Cloud Virtual Machine

Cloud Virtual Machine
FAQs
Product Documentation©2013-2022 Tencent Cloud. All rights reserved.

Page 1 of 131

Cloud Virtual Machine

Copyright Notice©2013-2024 Tencent Cloud. All rights reserved.
Copyright in this document is exclusively owned by Tencent Cloud. You must not reproduce, modify, copy or distributein any way, in whole or in part, the contents of this document without Tencent Cloud's the prior written consent.
Trademark Notice

All trademarks associated with Tencent Cloud and its services are owned by Tencent Cloud Computing (Beijing)
Company Limited and its affiliated companies. Trademarks of third parties referred to in this document are owned bytheir respective proprietors.
Service Statement
This document is intended to provide users with general information about Tencent Cloud's products and services
only and does not form part of Tencent Cloud's terms and conditions. Tencent Cloud's products or services are
subject to change. Specific products and services and the standards applicable to them are exclusively provided for in
Tencent Cloud's applicable terms and conditions.

©2013-2022 Tencent Cloud. All rights reserved.

Page 2 of 131

Cloud Virtual Machine

Contents
FAQs
Region and Availability Zone
Billing
Purchasing and Renewing
Instance
Issues on Logging in and Connecting to Instances
Purchasing
A CVM Instance Cannot Be Found
Usage
Use Limits
Adjusting Configuration
Spot Instances
Big Data Instance
OthersStorage
System Disks
Using Cloud Disks
Mounting and Unmounting Cloud Disks
Resizing Cloud Disks
Snapshots
Issues on Data Backup and Recovery
ImagesCustom Images
Copying Images
Issues on Custom Image
Changing Images (Reinstalling System)
Cloud-Init & Cloudbase-Init
FAQs about Red Hat Enterprise Linux Image
OthersService Migration
Network
IP Address
Elastic Public IP issues
Elastic Network Interface
Public Network Bandwidth©2013-2022 Tencent Cloud. All rights reserved.

Page 3 of 131

Cloud Virtual Machine

Network
Security
Passwords
Password Login and SSH Key Login
Security Groups
Security Group Rules
Port
FirewallOperating Systems
OPS & Monitoring
Uploading FilesOPS
Common Operations and Commands
Access Control
NTP Service
Use Cases©2013-2022 Tencent Cloud. All rights reserved.

Page 4 of 131

Cloud Virtual Machine

FAQs
Region and Availability Zone：

Last updated 2024-01-06 17:21:38

How can I view regions and availability zones?
To view regions and availability zones, try the followings:
Refer to Regions and Availability Zones document.
Use APIs to query regions and availability zones.
To view regions, use the DescribeRegions API.
To view availability zones, use the DescribeZones API.

What CVM regions and availability zones are available and how to choose?
For more information on available CVM regions and availability zones, see Regions and Availability Zones.
For more information on how to choose regions and availability zones, see How to Select the Region and Availability
Zone.

Can I change the region of a purchased CVM?
No. You cannot change the regions of purchased CVMs. If you need to deploy an existing CVM to another region oravailability zone, please try the following:
Terminate the instance and then purchase a new one.
Create a custom image for the original instance. Then, use the custom image to create an instance, launch it andupdate its configuration in a new availability zone.
1.1 Create a custom image for the current instance. For more information, see Create Custom Images.
1.2 If the network environment of the current instance is VPC and you need to retain the private IP address after
migration, please delete the subnet in the current availability zone and then create a subnet in the new availability zone
with the same IP address range as that of the original subnet.
Note:
If the subnet to be deleted contains available instances, first migrate all instances in the subnet to the new subnet.
1.3 Use the newly created custom image to create a new instance in the new availability zone.
You can choose the same instance type and configuration as that of the original instance, or configure new ones forthe new instance. For more information, see Creating an Instance.
1.4 If an elastic public IP address is associated with the original instance, disassociate it from the original instance andassociate it with the new instance. For more information, see Elastic IP Addresses (EIPs).
1.5 (Optional) If the pricing modes of the original instance is pay-as-you-go, you can terminate it. For more information,
see Terminate Instances.

©2013-2022 Tencent Cloud. All rights reserved.

Page 5 of 131

Cloud Virtual Machine

Can Tencent Cloud users in China enjoy the same product quality and services forresources purchased in China and other regions or countries?
Yes. Tencent Cloud China Console provides all users with the same product quality and services. The purchaseregion will not affect your user rights on the console.

Can I use the replication feature of a custom image to migrate a CVM in Mainland China toanother country or region?
No. Images can only be replicated within the same country or region. To replicate images between countries, pleasesubmit a ticket to apply.

What are the differences between instances in and outside Mainland China, and how do I
determine which region fits me the best?
Instances in other countries or regions are deployed outside Mainland China, providing geographical and market
advantages for global users. The fast local network can also meet international customer needs, which is suitable forusers who run businesses in other countries or regions.
For more information on supported regions, see Regions and Availability Zones.

Can I change between Linux and Windows operating systems for a CVM instance purchasedin a region outside Mainland China?
No. Switching OS between Windows and Linux is only available for CVM instances in Mainland China.

How do I apply for after-sale services for products purchased in regions outside Mainland
China?
If you purchased a product on the Tencent Cloud official website, call the Tencent Cloud 24/7 service hotline(4009100100) or submit a ticket.

How do I deploy CVM instances in regions outside China?
CVM instances in regions outside China have the same deployment method if they have the same type of operating
system.

Can I migrate instances to regions outside Mainland China?
The region and availability zone of an instance cannot be changed. To use an instance in other countries or regions,
you need to purchase another instance.

Why some instance types can only be purchased in China regions?
Some regions may not support certain instance types. For information on supported instance types, go to the CVM
purchase page to view instance purchase information.

©2013-2022 Tencent Cloud. All rights reserved.

Page 6 of 131

Cloud Virtual Machine

If I build a website using a CVM instance from a region outside Mainland China and myusers access the website through a domain name, does this domain name need ICP filing?
For websites in regions in Mainland China, ICP filing is required for domain names. For websites in other countries orregions, ICP filing is not required.

Do instances in different regions have the same price?
The pricing of a CVM instance includes its specifications, storage, network bandwidth, etc. The prices of thesecomponents vary by regions, so the instance price will be different.
For more information on pricing, see Pricing.

©2013-2022 Tencent Cloud. All rights reserved.

Page 7 of 131

Cloud Virtual Machine

Billing
Purchasing and Renewing：

Last updated 2024-01-06 17:26:45

Purchasing CVMs
What should I do if the CVM is not created successfully?
If it takes a long time to create a CVM, wait to see if the CVM is created successfully. If the creation fails, you can
submit a ticket to report your problems and receive assistance.

How do I terminate a CVM if it fails to be delivered?
You can submit a ticket to contact Customer Service and provide complete screenshots of the server information andtermination failure indicating delivery failure to facilitate troubleshooting.

Renewing CVMs
How do I renew an expired CVM?
For more information, see Renewing Instances.

How do I set auto renewal for CVMs?
For more information, see the steps for auto renewal in Renewing Instances.

Do pay-as-you-go instances need to be renewed?
For pay-as-you-go instances, charges are automatically deducted from the account every hour, so renewal is notneeded.

Other
Can I set auto release (termination) for CVM instances?
Yes. You can set auto release (termination) for pay-as-you-go instances and specify when to release them
automatically. For more information, see Terminating Instances.
If you have additional questions, please submit a ticket.

©2013-2022 Tencent Cloud. All rights reserved.

Page 8 of 131

Cloud Virtual Machine

I have purchased a Linux CVM with cloud disks that are over 20 GB. How will it be charged if
I reinstall the operating system as Windows?
The billing for the parts exceeding 20 GB of the previously purchased system disks will stop once the Windows OS issuccessfully installed.

I have purchased a Windows CVM with cloud disks. How will it be charged if I reinstall theoperating system as Linux?
Because the capacity of the system disk cannot be reduced, it needs to be reinstalled at the current capacity. You will
not incur additional charges. If you need to expand the system disk capacity after reinstalling the system as Linux, youwill incur additional fees. For more information, see System and Data Disks.
For more information on cloud disk prices, see Pricing List.
Note:
Changing OS is not supported for CVMs in regions outside the Chinese mainland.

What do the computing components in a CVM bill mean?
The computing components correspond to instance specifications. For example, the computing components for
S5.SMALL4 include the CPU, the memory, and the NVMe local disk.

©2013-2022 Tencent Cloud. All rights reserved.

Page 9 of 131

Cloud Virtual Machine

Instance
Issues on Logging in and Connecting to
Instances：

Last updated 2024-01-06 17:26:45

How do I log in to a CVM instance using VNC?
Tencent Cloud allows users to log in to a CVM instance by using the VNC web client. If you do not have a remote loginclient installed or cannot log in using the client, you can use a VNC web client to log in to a CVM instance. You can use
the web client to log in remotely, view the CVM instance status, and perform basic instance management. For detailed
instructions, refer to the following documents:
Logging into Linux Instances via VNC
Logging into Windows Instances via VNC

How do I enable multi-user remote login on a Windows server?
The Windows server supports multi-user remote login. For detailed configuration directions, refer to Setting Up Multiuser Remote Login for Windows CVMs.
If you fail to enable multi-user remote login on a Windows server after following the directions in the document above,
restart the instance and try logging in again.

How can I log in to an instance running Ubuntu as root?
The default user for Ubuntu is ubuntu . root is not enabled during the installation process by default. If
necessary, you can enable root by following the directions below:
1. Log in to the CVM instance using ubuntu .
2. ﻿Run the following command to set a password for root :©2013-2022 Tencent Cloud. All rights reserved.

Page 10 of 131

Cloud Virtual Machinesudo passwd root
3. Enter a password for root and press Enter.
4. Enter the password again and press Enter.
If the following message is displayed, the password was set successfully:©2013-2022 Tencent Cloud. All rights reserved.

Page 11 of 131

Cloud Virtual Machine

passwd: password updated successfully
5. Run the following command to open sshd_config :©2013-2022 Tencent Cloud. All rights reserved.

Page 12 of 131

Cloud Virtual Machinesudo vi /etc/ssh/sshd_config
6. Press i to switch to the editing mode. Find #Authentication and change the value of PermitRootLoginto yes , as shown in the following figure:Note:
If PermitRootLogin is commented, remove the comment marks ( # ).

©2013-2022 Tencent Cloud. All rights reserved.

Page 13 of 131

Cloud Virtual Machine

7. Press Esc and enter :wq to save the file and exit vi.
8. Run the following command to restart the SSH service.

©2013-2022 Tencent Cloud. All rights reserved.

Page 14 of 131

Cloud Virtual Machinesudo service ssh restart
9. Refer to Logging into Linux Instances Using the Standard Login Method on how to use the following information tolog in to your CVM instance running Ubuntu.
Username: root
Password: the password you set in Step 2.
A successful login using root is shown in the following figure:

What do I do if I cannot connect (log in) to my CVM instance after restarting it?
This problem may have been caused by the high CPU and memory usage of your instance. For more information,please refer to the following documents:
Failing to Log in to a Linux CVM Due to High CPU and Memory Usage
Failing to Log in to a Windows CVM Due to High CPU and Memory Usage

What do I do when I connect to my CVM instance remotely and the connection times out?
Make sure that:
The instance is running.
The instance is associated with security groups with the necessary security group rules. For detailed information, refer
to Adding Security Group Rules.
The instance has enabled SSH or RDP.
The instance has opened the corresponding ports. SSH uses port 22 by default and RDP uses port 3389 by default.

©2013-2022 Tencent Cloud. All rights reserved.

Page 15 of 131

Cloud Virtual Machine

Why is my remote connection to my Linux instance refused?
Make sure that:
The instance has enabled SSH or RDP.
The instance has opened the corresponding ports. SSH uses port 22 by default and RDP uses port 3389 by default.

Why do I get the invalid username or password message when I remotely connect to myLinux instance?
Make sure that:
You used the correct username. The default username for most Linux distributions is root . However, Ubuntu uses
ubuntu .
You entered your password correctly. If you forgot your password, reset it. For detailed directions, refer to Resetting
Instance Passwords.

Why do I get the invalid username or password message when I remotely connect to my
Windows instance?
Make sure that:
You used the correct username. The default username for Windows is Administrator .
You entered your password correctly. If you forgot your password, reset it. For detailed directions, refer to Resetting
Instance Passwords.
To use a user without administrator privileges to log in, that user needs to belong to the Remote Desktop Users group.

Does the Console support multi-user login via VNC?
No. If one user has already logged in, other users will not be able to log in.

What do I do if I forgot my CVM instance login password?
You can reset your password. For detailed directions, refer to Resetting Instance Passwords.

Why can’t I use Internet Explorer 8.0 to log in to my instances?
The VNC web client supports Internet Explorer 10 or later. Please download the latest version of Internet Explorer.
In addition, we recommend you use Google Chrome because the Tencent Cloud Console offers a better user
experience on Google Chrome than on Internet Explorer.

How do I log in to my Linux instance remotely?
Tencent Cloud recommends logging in to a Linux instance using the standard login mode. You can also:
Log in to a Linux instance using remote login software.
Log in to a Linux instance using SSH.
Log in to a Linux instance using VNC.

©2013-2022 Tencent Cloud. All rights reserved.

Page 16 of 131

Cloud Virtual Machine

What do I do if I cannot connect to my Linux instance?
If you cannot connect to your Linux instance, refer to Linux Instance Login Failures for troubleshooting instructions.
If this problem persists, please submit a ticket.

What do I do if I cannot connect to my Windows instance?
If you cannot connect to your Windows instance, refer to CVM Login Failure for troubleshooting instructions.
If this problem persists, please submit a ticket.

What do I do if I find that my CVM instance was logged into from unusual locations?
If you find that your CVM instance was logged into from locations you do not recognize:
1. Double check the login time from the unusual login location and check whether you or other administrators logged inat that time.
2. If no, follow the steps below:
2.1 ﻿Reset the password immediately.
2.2 Check your instance for viruses or trojans.
2.3 Use security groups to limit logins to specific IP addresses.

©2013-2022 Tencent Cloud. All rights reserved.

Page 17 of 131

Cloud Virtual Machine

Purchasing：

Last updated 2024-01-06 17:26:45

How do I purchase a CVM?
You can purchase both Tencent Cloud services and pay-as-you-go CVMs (billing is accurate to the seconds andsettled on an hourly basis) on the Tencent Cloud Console. For more information, see Billing Modes.

What instance types does CVM provide?
CVM provides multiple instance specifications. For more information, see Instance Types. You can select theappropriate instance type based on your business needs.
To manage sudden business surges, you can choose the pay-as-you-go billing method, which allows you toactivate/terminate instances at any time and only pay for resources that you actually use. Billing is accurate to theseconds to maximize your savings.

Can I purchase a Windows 2003 CVM?
Because Microsoft discontinued support for Windows Server 2003 and Windows Server 2003 R2 since July 14th,
2015, Tencent Cloud no longer provides the Windows 2003 server, which is not available for purchase.

What are some channels through which I can purchase CVMs?
You can purchase CVMs either from the Console or via an API.

When can I use the CVM I purchased?
After the CVM system installation is completed, you can log in to and use the CVM once its status becomes running.

How do I check which instances are available for purchase in a specific region or availabilityzone?
You can go to the CVM purchase page to view the instance types available in each region or availability zone.

What can I do if the resource of an instance I want to purchase is sold out?
If the resource of a specific instance you want to purchase is sold out, we recommend you:
Select another region
Select another availability zone
Select another resource
If the resource that you want to purchase is still not available after you take all of the measures above, try again later.
Instance resources are dynamic. When resources are insufficient, Tencent Cloud will replenish them as soon as
possible.

©2013-2022 Tencent Cloud. All rights reserved.

Page 18 of 131

Cloud Virtual Machine

How do I select a CVM instance that is suitable for my business?
Consider the following factors when you select a CVM instance. For more information about how to select a suitable
CVM instance for your business, see Instance Types.
Your business needs.
Your website type.
The average number of page views (PV) per day on your website.
The size of your homepage.
The data capacity of your website.

How do I pay for a CVM instance?
You can pay for a CVM instance online using your credit card.

How long does it take to launch a CVM?
Generally, it takes 1 to 2 minutes to create an instance. After the instance is created:
You can connect to the Linux instance by logging in to the Linux instance.
You can connect to the Windows instance by logging in to the Windows instance.
Note:
If an error occurs during instance creation, please submit a ticket.

I paid for a CVM instance but the instance was not created. Why did this happen?
If there are insufficient resources to create an instance of your selected type within the availability zone, the instancewill fail to be created. Your account will automatically be refunded the cost of the instance. If you do not receive arefund within 30 minutes, please submit a ticket.
You can go to the CVM purchase page to view the instance types available in each availability zone.

©2013-2022 Tencent Cloud. All rights reserved.

Page 19 of 131

Cloud Virtual Machine

A CVM Instance Cannot Be Found：

Last updated 2024-01-06 17:26:45

Problem Description
A purchased CVM instance cannot be found in the CVM console.

Possible Causes
1. ﻿The instance is not located in the current region﻿
2. ﻿You did not log in to the right console﻿
3. ﻿No instance is available under the current account﻿
4. ﻿The instance is released due to overdue payment or expiration﻿
5. ﻿The spot instance is automatically repossessed﻿
6. ﻿Refund is caused by insufficient resources﻿

Solutions
1. The instance is not located in the current region
If you did not switch to the region where the instance is located, you cannot find the instance. You can check this withthe following method.
Log in to the CVM console, and click Instances in the left sidebar. Switch to another region to check the instance atthe top of the page.

2. You did not log in to the right console©2013-2022 Tencent Cloud. All rights reserved.

Page 20 of 131

Cloud Virtual Machine

You maybe purchased a Lighthouse instance or another instance instead of a CVM instance, and you did not log in to
the right console.
Method 1: Go to Overview > Order Management, and check the prepaid and postpaid orders for the last threemonths. If the instance was purchased long ago, please click All time.

Method 2: View all the resources under your current account by clicking Overview > My Resources in the console.

3. No instance is available under the current account
You can find your account ID in an SMS you received related to CVMs.
The instance may not be purchased with an account under your name.

4. The instance is released due to overdue payment or expiration
If an instance is expired or with overdue payment, it will be released, and so you cannot find it in the console.

©2013-2022 Tencent Cloud. All rights reserved.

Page 21 of 131

Cloud Virtual Machine

Terminated instances cannot be recovered. You can check the Prepaid Service Expiration and Suspension
Notification via Message Center. If you did not receive a relevant message in Message Center, maybe you haveunsubscribed the notification.
If your account has overdue payment, please see Payment Overdue for status of the CVM instances and public
network bandwidth.

5. The spot instance is automatically repossessed
An allocated Spot Instance may be repossessed based on the prices or the relationship between supply and demand.
You will be notified via Message Center or metadata before the spot instance is terminated. You can check
Notification on Spot Instance Repossessing via Message Center. If you did not receive a relevant message in
Message Center, maybe you have unsubscribed the notification.

6. Refund is caused by insufficient resources
If you cannot find the newly purchased instance in the console, maybe it is because a refund is caused by insufficient
resources.
You can check the refund in Order Management, and then purchase again in another region or availability zone.

©2013-2022 Tencent Cloud. All rights reserved.

Page 22 of 131

Cloud Virtual Machine

Usage
：

Last updated 2024-01-06 17:26:45

How do I view CVMs that are currently in use?
You can log in to the CVM console to view CVMs that are currently in use.

Can VM be installed on a CVM?
No.

How do I shut down an instance?
For more information, see Shutdown Instances.

How do I restart an instance?
For more information, see Restarting Instances.

How do I terminate an instance?
For more information, see Terminating Instances.

How do I query the username and password of a Linux instance?
After you create a CVM instance, its username and password will be delivered to your account through the Message
Center. The admin account of a Linux instance is root by default.

How do I query, partition, and format the disks of a Linux instance?
You can run the df -h command to query the total and used disk capacities and run the fdisk -l command
to view the disk information. For information about how to partition and format the disks of Linux instances, see
Initializing Cloud Disks (Smaller than 2TB) and Initializing Cloud Disks (Larger than 2TB).

How do I upload files to a Linux instance?
You can use SCP to upload files to a Linux instance.
You can use FTP to upload files to a Linux instance.

How do I change the owners and owner groups of directories and files on a Linux instance?
If the file or directory permissions are incorrectly configured on the Web server, a 403 error will occur when you accessa website hosted on the instance. Therefore, before you adjust a file or directory, you must confirm the identity underwhich the file or directory process is running.
You can run the ps and grep commands to query the identities under which the file or directory process isrunning.

©2013-2022 Tencent Cloud. All rights reserved.

Page 23 of 131

Cloud Virtual Machine

You can run the ls –l command to query the owners and owner groups of files and directories.
You can run the chown command to modify the permissions. For example, you can run the chown -R www.www/tencentcloud/www/user/ command to change the owners and owner groups of all files and directories under
the /tencentcloud/www/user directory to account "www".

Do Linux instances support GUI?
Yes. If you need to build a GUI in a Linux instance, see Building a Visual Ubuntu Desktop.

Why can’t I add sound or video cards to CVM instances?
Tencent Cloud CVMs do not provide multimedia servers and sound and video card components by default. Therefore,sound and video cards cannot be added to CVM instances.

Can I specify a MAC address when purchasing a CVM instance?
No. A MAC address is randomly assigned when a CVM instance is created and cannot be specified.

Can I transfer the unused time of a CVM instance to another CVM instance?
No. If you want higher flexibility and cost-efficiency, we recommend that you purchase pay-as-you-go instances.

How do I query the region where the IP address of a CVM instance is located in?
The IP address of a CVM instance is located in the same region where you purchased the CVM instance.

Do CVM instances provide databases by default?
No. To use database services, you can:
Deploy your own database. For example, you can install and build MySQL.
Purchase TencentDB for MySQL separately.
Configure the environment database using the image marketplace.

Can I build a database on a CVM instance?
Yes. You can install database software and configure a database environment on a CVM instance as needed. You
can also purchase TencentDB for MySQL separately.

When can I forcibly stop a CVM instance? What are the consequences of forcibly stopping a
CVM instance?
You can forcibly stop a CVM instance when normal shutdown fails. Please note that forced shutdown is equivalent toa power outage and can result in the loss of unsaved data.

©2013-2022 Tencent Cloud. All rights reserved.

Page 24 of 131

Cloud Virtual Machine

Use Limits：

Last updated 2024-01-06 17:26:45

What are the limitations of changing public IP addresses of CVM instances?
The limitations of changing public IP addresses of CVM instances are:Each account can change public IP addresses in the same region a maximum of 3 times per day.
Each instance can only change its public IP once.
The old public IP will be released after the public IP is changed.

How many websites can be hosted on a CVM instance?
A CVM instance can host up to 5 websites, and each website can bind to multiple domain names.

Can a CVM instance access the Amazon website?
Yes, as long as your CVM instance can connect to the public network properly.

How do I purchase more pay-as-you-go CVMs?
If you have reached the maximum number of pay-as-you-go instances that you can purchase, you cannot purchasemore pay-as-you-go instances. For more information, see Purchase Limits.

How can I query the CVM resource quota?
To query the use limits and quotas of CVM resources, see CVM instance use limits in Use Limits Overview.

©2013-2022 Tencent Cloud. All rights reserved.

Page 25 of 131

Cloud Virtual Machine

Adjusting Configuration：

Last updated 2024-01-06 17:26:45

How do I upgrade/downgrade the configurations of CVMs?
You can only adjust the configurations of instances whose system disks and data disks are both cloud disks.
For more information about how to upgrade/downgrade instance configurations, see Changing InstanceConfigurations.
For more information about how to adjust bandwidth/network configurations, see Adjusting Network Configurations.
If your configuration adjustments do not take effect, please submit a ticket to contact us.

How do I check the records of configuration adjustments?
1. Log in to the CloudAudit Console.
2. On the Event history page, set filters such as the username, the resource type, and the resource name as needed
to view the record list.
For more information, see Getting Started.

Can I adjust the configurations of CVM instances?
Yes. You can adjust the configurations of instances whose system disks and data disks are both cloud disks. For payas-you-go instances, you can upgrade or downgrade their configurations as many times as you want.

What is the maximum number of times I can downgrade the configurations of CVMs?
You can upgrade or downgrade the configurations of pay-as-you-go instances as many times as you want.

Can I upgrade the specifications and the configurations of pay-as-you-go instances?
Yes. You can upgrade the configurations of pay-as-you-go CVM instances by following the directions listed in
Changing Instance Configurations or through the ResetInstancesType API.

How long does it take to upgrade a CVM instance?
About 1 to 2 minutes.

How is the cost incurred for a CVM instance upgrade calculated?
You can view the cost details at the Billing Center after you upgrade the specifications or the configurations of the
CVM instance.

Will upgrading CVM instances affect my business configurations on the instance?
After you upgrade a CVM instance, you must restart it to validate the new configurations. The upgrade operation willinterrupt your business for a short period of time. We recommend that you upgrade instances when business is slow.

©2013-2022 Tencent Cloud. All rights reserved.

Page 26 of 131

Cloud Virtual Machine

After being upgraded, instances will seamlessly resume your business and will not require environment
reconfiguration.

Why is the estimated refund of a CVM downgrade 0?
One possible reason is that you have purchased the instance at a discount but the downgraded configuration is
calculated according to the original price of the instance. When the price of the instance purchased at a discount islower than or equal to the original price of the instance, the estimated refund will be displayed as 0.

Why did the instance upgrade not take effect?
After you upgrade an instance, you must restart it on the Console or through an API.

©2013-2022 Tencent Cloud. All rights reserved.

Page 27 of 131

Cloud Virtual Machine

Spot Instances：

Last updated 2024-06-25 15:43:07

Instance Release
Why is a spot instance released automatically?
An important feature of spot instances is that the system will repossess assigned instances based on prices or the
supply-demand relationship. If the market price is higher than your bid or if the CVM resource pool corresponding to
your spot instances is in short supply, the process will be interrupted by the system.

Is it possible to avoid being repossessed by the system through bidding?
No. Because repossession trigged by insufficient inventory is unavoidable. You need to accept that instancerepossession may occur when you deploy businesses on the spot instance.

How do I know that an instance is about to be interrupted?
Two minutes before the interruption, we will notify you in the form of metadata that the instance is about to beinterrupted and repossessed.
For more information, see Querying the Repossession Status of a Spot Instance.

How to automatically apply for spot instances after inventory recovery?
You can use cloud products that can automatically maintain the CVM cluster, such as BatchCompute, Auto Scaling.
With their cross-model and cross-availability zone capabilities, you can maintain a specified number of CVM clusters
more effectively.

Price and Billing
What are the similarities and differences between spot instances and pay-as-you-go
instances?
Billing Method

Similarities

Differences

Spot
instances

Both of them are pay-as-you-go. There is no need to
pay in advance but certain costs must be frozen. You
can enable/terminate the CVM at any time and pay
according to actual usage. The billing time granularity

Price: In the vast majority of cases,
the price of spot instances is3%-20% of the pay-as-you-go priceunder the same specification, andis accurate to the second, and the account will besettled every hour.

fluctuates in response to market
supply and demand dynamics.

Pay as you go©2013-2022 Tencent Cloud. All rights reserved.

Page 28 of 131

Cloud Virtual Machine

Release mechanism: The lifecycleof a pay-as-you-go instance iscontrolled by the user, while spot
instance may be actively
repossessed by the system.
Feature limitations: Spot instances
Configuration adjustments are notallowed.

Which price, the market price and the highest bid specified by the user, will be used forbilling?
The market price will be used for billing. You can specify a high bid to prevent instances from being repossessed dueto the price. However, the system will only charge you at the current market price (the current market price will be
fixed).

How are billing periods calculated for spot instances?
You will be billed for the period from the moment you apply for a spot instance to the moment the spot instance ismanually released or interrupted by the system. The billing period is accurate to the second.

Where can I find the current market prices of all the spot instances?
During the beta testing period, we cannot provide a page where you can query the market prices of all instances, but it
will be available in the future. Currently, most of the spot instances will be priced at 20% of the regular pay-as-you-go
instances of the same model and specification.

Where can I view the consumption details regarding spot instances?
As with pay-as-you-go instances, you can find detailed usage and billing information of spot instances in Billing
Center > Bills at the top of the console. Spot instances are pay-as-you-go services.

Quotas and Limitations
In which regions are spot instances available? Which instance models and specifications do
spot instances support?
RegionModels Supportedby Spot Instances

Beijing, Shanghai, Chengdu, Chongqing, andGuangzhou OpenAll models
supported by pay-©2013-2022 Tencent Cloud. All rights reserved.

Discounts

3%-20% off the published prices ofPage 29 of 131

Cloud Virtual Machine

Guangzhou (excluding Guangzhou Zone 1)

as-you-go
instancespay-as-you-go instances with thesame specifications

Hong Kong (China), Singapore, Bangkok,
Seoul, Tokyo, Mumbai, Toronto, Silicon Valley,
Virginia, and Frankfurt

Are quota limits of spot instances shared by pay-as-you-go instances?
No. Each user can have up to 50 spot instance vCPU cores in each availability zone. To raise the quota limits, submit
a ticket.

Can I upgrade or downgrade the specifications of spot instances?
No.

Do spot instances support no charges when shut down?
No.

Do spot instances support system re-installation?
No.

Can I use vouchers for purchasing spot instances?
No.

©2013-2022 Tencent Cloud. All rights reserved.

Page 30 of 131

Cloud Virtual Machine

Big Data Instance：

Last updated 2024-01-06 17:26:45

What is a big data instance?
Big data instances are designed specifically for scenarios like Hadoop distributed computing, massive log processing,
distributed file system, large data warehouse, and more. This CVM instance type is mainly used to solve the cloudcomputing and storage problems of massive business data.

Which industry customers and business scenarios are big data instances applicable to?
Big data instances are applicable to customers in the Internet, game, finance and other industries that require big data
computing and storage analysis, as well as business scenarios that require massive data storage and offline
computing. They can meet the storage, capacity and private network bandwidth requirements of distributed
computing businesses represented by Hadoop.
In addition, with the highly available architectural framework of distributed computing services such as Hadoop, bigdata instances use local storage, making the total cost close to that of a self-built Hadoop cluster in IDC, while
ensuring massive storage capacity and high performance.

Features
A single instance has a throughput capacity up to 2.8 GB/s. HDD local disk is ideal for throughput-intensive storage.
With stable and high-performing sequential read/write throughput, big data instances are designed specifically for
Hadoop distributed computing, massive log processing, large data warehouse and other business scenarios.
Local storage has a unit price as low as 1/10 of S2 instances, making its total cost close to that of a self-built Hadoop
clusters in IDC while ensuring massive storage capacity and high performance. Big data instances deliver the optimal
cost-efficiency for big data scenarios.
Read/write latency is as lows as 2-5ms. Big data instances are high-performing models suitable for enterprisedevelopers.
It supports the pay-as-you-go billing method.

Specifications
Note:
For more information on instance specifications, see the “Big Data Family” section in Instance Types.

Notes on local data storage
Big data instances use local disk as the data disk, which may lose data (e.g., when the host crashes). If yourapplication cannot guarantee data reliability, we recommend you choose an instance that can use cloud disks as thedata disk.

©2013-2022 Tencent Cloud. All rights reserved.

Page 31 of 131

Cloud Virtual Machine

The table below shows you the local disk data status after you perform different operations on an instance with thelocal disk.
Operation

Local Disk
Data Status

Description

Log in to an instance to restart it, restart an instance on the
console, or forcibly restart an instance

Retained

Local disk storage as well as
the data is retained.

Log in to an instance to shut it down, shut down an instance on
the console, or forcibly shut down an instance

Retained

Local disk storage as well as
the data is retained.

Terminate (instance) on the console

ErasedLocal disk storage is erased.
No data is retained.

Note:
Do not store business data that needs to be retained for a long time on a local disk. Back up data in advance and use
a highly available architecture. We recommend you store the data on a CBS disk for long-term retention.

How can I purchase a local disk for big data instances?
Local disk can only be purchased when a big data instance is created. The instance specifications determine thenumber and capacity of local disks you can purchase.

Does the local storage of big data instances support snapshot?
No.

Does a big data instance support configuration adjustment and failover?
No.
Big data instances feature massive data storage and use local HDD as data disk. To prevent data loss (when the hostcrashes or local disk is damaged), we recommend you use a redundancy policy, for example, a file system that
supports redundancy and fault tolerance (such as HDFS and Mapr-FS). We also recommend you regularly back up
data to a persistent storage system, such as Tencent COS. For more information, please see Cloud Object Storage.
If the local disk is damaged, you will need to shut down the CVM instance for us to replace the local disk. We will notify
you and perform fixes if the CVM instance crashes.

What is the difference between the Big Data family and High IO I2 instances?
High IO I2 instances featuring ultra-high IOPS are designed specifically for business scenarios with low latency andhigh random IO. They are suitable for high-performance database (relational database, NoSQL, etc.). Big data
instances are designed specifically for business scenarios that require high sequential read/write and low-cost
massive data storage. This type features high storage cost-efficiency and private network bandwidth.

©2013-2022 Tencent Cloud. All rights reserved.

Page 32 of 131

Cloud Virtual Machine

How is the disk throughput of big data instances?
Big data D2 instances boast local disks with the sequential read/write throughput as follows.
For a single disk, the sequential read throughput is 220+ MB/s and sequential write throughput is 220+ MB/s (block
size of 128 KB and queue depth of 32).
For the CVM, the throughput can reach up to 2.8 GB/s (block size of 128 KB and queue depth of 32).

What is the difference between the local disk of big data instances and CBS?
Cloud Block Storage is a highly available, highly reliable, low-cost, and customizable block storage device. It can beused as an independent and scalable disk for CVM, providing efficient and reliable storage devices. It provides data
storage at the data block level and employs a three-copy distributed mechanism to ensure data reliability for CVM
instance, meeting the requirements of different use cases. The local disk of big data instances is designed specificallyfor business scenarios that require high sequential read/write for massive local data sets, such as Hadoop distributed
computing, large-scale parallel computing, and data warehouse.

©2013-2022 Tencent Cloud. All rights reserved.

Page 33 of 131

Cloud Virtual Machine

Others：Last updated 2024-01-06 17:26:45

How do I view the operation logs of a CVM?
You can view the operation logs of a CVM on the console as follows:
1. Log in to the CVM console and select Tool > Operation Log in the top-right corner.
2. Select CVM for the resource event and configure other filters as needed.
3. Click Query to obtain the CVM operation logs.
For more information about CloudAudit operation records, see Viewing the Event Details of Operation Records.

What if I cannot find my CVM in the console?
The reasons why a purchased CVM instance cannot be found in the CVM console include:
1. The instance is not located in the current region.
2. You did not log in to the right console.
3. No resource is available under the current account.
4. The instance is released due to overdue payment or expiration.
5. The spot instance is automatically repossessed.
6. Refund is caused by insufficient resources.
For detailed solutions, see A CVM Instance Cannot Be Found.

How to view the CPU frequency of a CVM?
The frequency viewed via /proc/cpuinfo on a Linux instance is only the base frequency, because someprivileged registers on the virtual machine cannot be accessed and the underlying real-time running frequency
information of the CPU cannot be read. For information on CPU models and frequencies of instances, see Instance
Types.

How to enable turbo frequency for a CVM?
Turbo frequency is enabled automatically when a CVM is running. The processor will automatically adjust the runningfrequency based on the CPU loading requirements of the application. The max turbo frequency can be reached whena CPU intensive application is running.

©2013-2022 Tencent Cloud. All rights reserved.

Page 34 of 131

Cloud Virtual Machine

Storage
System Disks：

Last updated 2024-01-06 17:26:45

What is the default capacity of a CVM system disk?
Currently, a new CVM system disk has a default capacity of 50 GB.

Can I change a CVM system disk from a local disk to a cloud disk?
When purchasing a CVM instance,
you can select the desired disk type for the CVM system disk.
After purchasing a CVM instanceif there are available cloud disks in the availability zone where the purchased CVM resides, you can use the change
disk media type feature to change the local system disk to a cloud disk.

Which regions and availability zones support expanding the system disk capacity to morethan 50 GB?
If the system disk is a cloud disk, the system disk capacity can be adjusted to more than 50 GB in all regions that
support snapshots.

Can I expand the system disk capacity of a CVM instance when reinstalling the operating
system?
It depends on the system disk type.
If the system disk is a cloud disk,
the system disk capacity cannot be expanded.
If the system disk is a local disk,
it depends on the system disk size.
If the default system disk capacity of the purchased instance is 50 GB, the system disk cannot be expanded.
For instances purchased at an earlier time: if the system disk capacity is 20 GB or less, the system disk can be
expanded to 20 GB by default. If the system disk capacity is more than 20 GB, the system disk can be expanded to 50
GB by default.

Can I reinstall the operating system to reduce the system disk capacity after the expansion?
The capacity of a system disk cannot be reduced.

How do I save the data on the CVM instance and then expand the system disk capacity?
For detailed directions, see Expanding Cloud Disks.

©2013-2022 Tencent Cloud. All rights reserved.

Page 35 of 131

Cloud Virtual Machine

What is the system disk capacity if I use an image of less than 50 GB to create or reinstall
the CVM?
The image capacity does not affect the system disk capacity. The minimum system disk capacity is 50 GB.

Does the CVM system disk support partitioning?
Yes, but we recommend you not partition a system disk.
If you partition the system disk with a third-party tool, system crash or data loss may occur. You can performpartitioning after expanding the system disk capacity.

©2013-2022 Tencent Cloud. All rights reserved.

Page 36 of 131

Cloud Virtual Machine

Using Cloud Disks：

Last updated 2024-01-06 17:26:45

How can I view the data disk?
1. Log in to the CVM console.
2. Click Cloud Block Storage in the left sidebar to access the Cloud Block Storage management page.
3. Click the filter icon next to the Attribute column title, select Data disk and click OK to view all data disks in theregion.

How do I read and write the original NTFS data disk after the Windows operating system isreinstalled to Linux?
Windows employs two major file systems, NTFS or FAT32, while EXT is the file system for Linux. When an operating
system is changed from Windows to Linux after reinstallation, the data disk remains in its original format. Therefore,
the system might be unable to access data disk’s file system. In these cases, you will need to use a format converter
to read the data disk. For details, see Reading/Writing NTFS Data Disks after Reinstalling a Windows CVM to LinuxCVM.

How do I read the data disk in EXT format after the Linux operating system is reinstalled toWindows?
Windows employs two major file systems, NTFS or FAT32, while EXT is the file system for Linux. When an operating
system is changed from Linux to Windows after reinstallation, the data disk remains in its original format. Therefore,
the system might be unable to access data disk’s file system. In these cases, you will need to use a format converter
to read the data disk. For details, see Reading/Writing EXT Data Disks after Reinstalling a Linux CVM to Windows
CVM.

What are the differences among Premium Cloud Storage, SDD and Enhanced SSD?
Premium Cloud Storage: Tencent Cloud Premium Cloud Storage is a hybrid storage type. It adopts the Cache
mechanism to provide a high-performance SSD-like storage, and employs a three-copy distributed mechanism toensure data reliability. Premium Cloud Storage is suitable for small and medium applications with high requirements
for data reliability and standard requirements for performance.
SSD: SSD uses NVMe SSD as the storage media, and employs a three-copy distributed mechanism. It provides highperformance storage with low latency, high random IOPS, high throughput I/O, and data security up to 99.9999999%,
making it suitable for applications with high requirements for I/O performance.
Enhanced SSD: Enhanced SSD is based on Tencent Cloud’s latest storage engine, NVMe SSD storage media andthe latest network infrastructure. It employs a three-copy distributed mechanism to provide high-performance storage
with low latency, high random IOPS, high throughput I/O, and data security up to 99.9999999%, making it suitable for
I/O-intensive applications with high requirements for latency, such as large databases and NoSQL.

©2013-2022 Tencent Cloud. All rights reserved.

Page 37 of 131

Cloud Virtual Machine

Pricing of the three types of cloud disks varies with region. You can select the cloud disk that best suits yourapplication requirements and budget. For pricing details, see Price Overview.
For more information on disk types and performance, see Cloud Disk Types.

How do I test the disk performance?
We recommend using FIO to perform stress test and verification on cloud disks. For instructions, see Measuring
Cloud Disk Performance.

What are the most common cloud disk operations?
For common cloud disk operations, see Operation Overview.

How do I check the available and used space on the cloud disks?
You can log in to the CVM instance to check the available and used space on the cloud disks. This information canalso be seen on the CVM console as follows.
1. Log in to the CVM console and access the Instances page.
2. Select the ID/Name of the target instance to access the details page.
3. Click on the Monitoring tab to view the instance disk usage:

Why was the cloud disk I separately created released together with my instance?
When mounting a cloud disk, you can decide if it should be released with the instance automatically. This can be
configured via the CBS console or ModifyDiskAttributes API.

How do I partition and format the a mounted cloud disk?
For more information, see Initializing Cloud Disks (Smaller than 2TB) or Initializing Cloud Disks (Larger than 2TB).

©2013-2022 Tencent Cloud. All rights reserved.

Page 38 of 131

Cloud Virtual Machine

Mounting and Unmounting Cloud Disks：

Last updated 2024-01-06 17:26:45

What is a device name (mount point)?
A device name (mount point) is the location of a cloud disk mounted to the CVM instance on the disk controller bus.
The selected device name matches the disk device number in Linux and matches the disk sequence number of thedisk manager in Windows.

Can I mount one cloud disk to multiple CVM instances?
No. You can mount up to 20 cloud disks to the same CVM, but you cannot mount the same cloud disk to multiple
CVMs. You can only share data by unmounting the cloud disk from CVM A and then mounting it to CVM B.

Do I need to partition the cloud disk after purchasing and mounting it to a CVM instance?
Yes. After you purchase a cloud disk, you must mount it to a CVM instance in the same availability zone, and theninitialize it by formatting, partitioning, and creating the file system before using it as a data disk. For more information,
see Mounting Cloud Disks and Initializing Cloud Disks.

Why am I unable to locate the data disk that I purchased for a Linux instance?
If you purchase a data disk separately, you must partition, format, and mount it to an instance to view and use its
storage space. For more information, see Mounting Cloud Disks and Initializing Cloud Disks.

How many cloud disks can be mounted to one CVM instance?
A maximum of 20 data disks can be mounted to one CVM instance.

Why can’t I locate the CVM to which I want to mount a cloud disk?
Make sure that the CVM instance has not been released and ensure that it is in the same region and availability zone
as the cloud disk is in.

Can I mount a cloud disk to a CVM instance in another availability zone?
No. A cloud disk can only be mounted to or unmounted from a CVM instance in the same availability zone as the cloud
disk is in.

When I unmount a cloud disk (data disk), will its data be lost?
Data in cloud disks will not be modified during mounting or unmounting. To ensure data consistency, we recommendthat you follow the steps below:
In Windows, we recommend that you stop all read and write operations on all file systems of the cloud disk to ensure
data integrity. Otherwise, the data that has not finished being read or written will be lost.

©2013-2022 Tencent Cloud. All rights reserved.

Page 39 of 131

Cloud Virtual Machine

In Linux, log in to the CVM instance and run the umount command on the cloud disk. After the command is
executed, log in to the CVM Console to unmount the cloud disk.

How do I unmount a cloud disk?
For more information, see Unmounting Cloud Disks.

Can cloud disks be mounted and unmounted?
Cloud disks can be mounted and unmounted.
System disks cannot be mounted or unmounted.

Can cloud disks be mounted and unmounted in batches?
Cloud disks can be mounted and unmounted in batches.
System disks cannot be mounted or unmounted.

Can system disks be unmounted?
No.

©2013-2022 Tencent Cloud. All rights reserved.

Page 40 of 131

Cloud Virtual Machine

Resizing Cloud Disks：

Last updated 2024-01-06 17:26:45

How do I expand the capacity of a cloud disk?
If your CVM uses a cloud disk, you can expand the disk capacity. For more information on how to expand the disk
capacity, see Expanding Cloud Disks.

Can I reduce the capacity of a cloud disk?
No. If you want to reduce the capacity of a cloud disk you purchased, we recommend that you create a cloud disk ofyour desired capacity and mount it to the same instance that the original cloud disk is mounted to. Then, copy the datastored in the original disk to the new disk and release the original disk.

How do I expand a system disk?
For data security reasons, a CVM system disk cannot be expanded directly on the Console. You must reinstall theoperating system of the instance to expand the capacity of its system disk.

Can the system disks of all types of cloud disks be expanded?
Yes. The system disks of all types of cloud disks, including SSD, Premium Cloud Storage, and HDD, can be
expanded.

Can the system disks of pay-as-you-go CVM instances be expanded?
Yes. The system disks of pay-as-you-go CVM instances can be expanded.

What is the capacity range of the system disk? What is its maximum capacity?
The expanded system disk’s capacity must be greater than its existing capacity but less than or equal to 500 GB.

©2013-2022 Tencent Cloud. All rights reserved.

Page 41 of 131

Cloud Virtual Machine

Snapshots：

Last updated 2024-01-06 17:26:45

Is snapshot available in all availability zones?
Yes.

Will creating a snapshot affect the disk performance?
Creating a snapshot will occupy a small amount of the cloud disk I/O. We recommend creating snapshots whenbusiness is slow.

How long does it take to create a snapshot?
The time it takes to create a snapshot is influenced by factors such as the number of disk writes and the underlying
read-write operations. Creating a snapshot will not affect your disk use.

Do I need to shut down the CVM to roll back snapshots?
For a cloud disk that has been mounted to a CVM, you have to shut down the CVM to roll back snapshots.
For a cloud disk that has not been mounted, you can directly roll back snapshots.

How is the size of the first full snapshot of a cloud disk calculated?
The first snapshot created on a cloud disk is a full snapshot that copies all the data of the cloud disk at a point in time.
The snapshot size equals the used capacity of the cloud disk. For example, if the total capacity of a cloud disk is 200
GB and 122 GB have been used, the size of the first full snapshot is 122 GB.

Can I download or export CVM instance snapshots to a local device?
No. Snapshots cannot be downloaded or exported to local devices. You need to create a custom image from asnapshot and then export the image.

Do automatic snapshots differ from or conflict with manual snapshots?
No. You can use both of them at the same time. However, you cannot create manual snapshots while automatic
snapshots are being created.
You cannot create a custom disk snapshot until the automatic disk snapshot has finished being created, and viceversa.
If one snapshot created from a large disk lasts longer than the interval between two automatic snapshots, the next
automatic snapshot will be skipped. For example, if you configure the automatic snapshots to be created at 9:00,
10:00, and 11:00 and the automatic snapshot created at 9:00 lasts for 70 minutes and ends at 10:10, the next
automatic snapshot will be created at 11:00 and not at 10:00.

©2013-2022 Tencent Cloud. All rights reserved.

Page 42 of 131

Cloud Virtual Machine

Can I create snapshots for local disks?
No. We recommend that you use data redundancy at the application layer or create deployment sets for clusters to
improve the availability of applications.

After I release the cloud disk, will local snapshots be deleted?
No. You need to delete snapshots via the Console or APIs. For more information, see Deleting Snapshots.

Why does the used disk capacity displayed in the file system differ from the snapshot size?
A cloud disk snapshot is a block-level clone or backup. In general, the snapshot capacity will be larger than the datacapacity displayed in the file system because:
The underlying data block stores the metadata of the file system.
Some data are deleted. Deleting data modifies the written-in data block, which will be backed up to snapshots.

How can I prevent snapshots from being deleted by Tencent Cloud?
Manual snapshots: Tencent Cloud will never delete them, regardless of whether their corresponding disk or instancehas been released.
Scheduled snapshots: you can set the retention period of scheduled snapshots to long-term retention to prevent themfrom being deleted. This way, only the snapshot created earliest will be deleted when the snapshot quota is reached.
For detailed directions, see Scheduled Snapshot and Use Limits.

How can I delete snapshots to reduce backup costs?
For cloud disk snapshots, you can delete them directly via the Console or APIs. For more information, see Deleting
Snapshots.
For snapshots associated with custom images, you must first delete the custom images and then delete thesnapshots.

Will automatic snapshots be deleted after the instance expires or the cloud disk is released?
No. Automatic snapshots will not be deleted after the instance expires or the cloud disk is released because they areretained based on the retention period policies of scheduled snapshots. To modify the policies of scheduledsnapshots, see Scheduled Snapshot.

How can I delete snapshots from which an image or cloud disk was created?
Snapshots from which a cloud disk was created: you can delete the snapshots separately. After you delete asnapshot, you will not be able to operate a business that depends on the original snapshot data.
Snapshots from which a custom image was created: you have to first delete the image and then delete the snapshots.
Snapshots from which an instance was created: you can delete the snapshots separately. After you delete a snapshot,
you will not be able to operate a business that depends on the original snapshot data.

©2013-2022 Tencent Cloud. All rights reserved.

Page 43 of 131

Cloud Virtual MachineWill the snapshot policy fail to be executed if I create a custom image or cloud disk basedon the scheduled snapshot?
No.

Can a cloud disk have multiple automatic snapshot policies?
No.

How can I prevent data loss caused by incorrect operations?
You can create snapshots to back up data before you perform risky operations. For example, you can create asnapshot before you modify critical system files, migrate instances from a classic network to a VPC, back up data,
restore an instance that was released accidentally, prevent network attacks, change operating systems, or provide
data support for a production environment. For more information, see Creating Snapshots. If an error occurs, you canroll back snapshots to reduce risks.

I created an instance in the Guangzhou region and created snapshots for the data disks of
the instance. After the instance expired and was released, I purchased another instance in
the Guangzhou region. Can I roll back the snapshots on the new instance to restore theoriginal instance?
No. Snapshots can only be rolled back to the cloud disk in which they are created. You can use the snapshots of theprevious data disk to create a cloud disk and mount the cloud disk to the new instance. For more information, see
Creating Cloud Disks Using Snapshots and Mounting Cloud Disks.

What are the differences between snapshots and images?
If no data disk is mounted to an instance and all data is written on the system disk, the data on the system disk cannot
be protected by creating an image. Images cannot be scheduled for continuous backup. Once the system disk data isdamaged, you can only recover the data to the state when the image was initially created. Therefore, images are notsuitable for data protection. Specific differences are as follows:
Name

Snapshots

ImagesCharacteristics

Backup data of a cloud disk at a
certain point in time

CVM software configuration template, whichcontains information about the operating systemand pre-installed programs

Use Cases

Regularly back up important businessdata
Back up data before major operations
Produce multiple copies of data

Back up systems that will remain unchanged in
the short term
Deploy applications in batches
Migrate the system

How can I migrate snapshot data from account A to account B?

©2013-2022 Tencent Cloud. All rights reserved.

Page 44 of 131

Cloud Virtual Machine

Snapshots cannot be migrated. Instead, you can create an image from the snapshot that you want to migrate andshare the image with another account.

Can I create a custom image from data disk snapshots?
No. You can only create a custom image from system disk snapshots.

©2013-2022 Tencent Cloud. All rights reserved.

Page 45 of 131

Cloud Virtual Machine

Issues on Data Backup and Recovery：

Last updated 2024-01-06 17:26:45

How do I back up data for CVM?
If your CVM uses a cloud disk, you can back up your business data by creating a system disk custom image and adata disk snapshot.
For more information on how to create a custom image, see Create Custom Images.
For more information on how to create a snapshot, please see Creating Snapshots.
If your CVM uses a local disk, you can back up data on system disk by creating a custom image. For business data inyour data disk, you still need to customize the backup policy.
You can use FTP to back up data in the server to other places. For specific FTP deployment methods, see:For Windows: Build the FTP Service (Windows)
For Linux: Build the FTP Service (Linux)

What are common data backup and recovery solutions?
The data backup and recovery solutions vary by application scenarios and businesses. The following
recommendations can be used based on your actual needs:
Back up the instance regularly using the CBS Snapshot feature.
Deploy key components of an application across multiple availability zones, and copy the data as needed.
Use Elastic Public IP for domain name mapping to ensure that the service IP can be quickly redirected to another
CVM instance when the server is unavailable.
View the monitoring data regularly and configure corresponding alarms. For more information, please see Cloud
Monitor.
Process emergency requests with auto scaling. For more information, please see Auto Scaling.

©2013-2022 Tencent Cloud. All rights reserved.

Page 46 of 131

Cloud Virtual Machine

ImagesCustom Images：

Last updated 2024-01-06 17:26:45

What should I do if the Windows system fails to create a custom image?
If the Windows system fails to create a custom image, you can troubleshoot the issue as follows:
1. The creation of a custom image relies on the Windows Modules Installer provided by Microsoft. Make sure thisservice is working properly.
2. Some antivirus tools or Safedog may block custom image creation scripts from being executed. To avoid creation
failure, we recommend you disable these tools before creating a custom image.
3. If the image creation tool is interrupted by system pop-ups, remotely log in to the CVM and check and adjust theCVM configuration to block pop-ups.

Can a custom image be created from the data disk snapshot?
No. A custom image can be created from the system disk snapshot, but not from the data disk snapshot.
If you need to keep the data on the data disk of the original instance when launching a new instance, you can first takea snapshot of the data disk, and then use this data disk snapshot to create a new CBS data disk. For more
information, see Creating Cloud Disks using Snapshots.

Do local disks support custom images?
If the system disk of an instance is a local disk, you can create custom images.
If the data disk of an instance is a local disk, you can create only images of the system disk of the instance.

How do I confirm that a data disk has been unmounted and a custom image can be created?
1. Confirm that the partition statement row of the automatically mounted data disk has been deleted in the/etc/fstab file.
2. Execute the mount command to query the mounting information of all devices. Ensure that the execution result
does not include the corresponding data disk partition information.

Will the custom image still exist after the instance is released?
Yes.

Can I change the operating system of an instance created from a custom image? After Ichange the operating system, will I still be able to use the original custom image?
Yes. You can continue to use the original custom image after changing the operating system.

©2013-2022 Tencent Cloud. All rights reserved.

Page 47 of 131

Cloud Virtual Machine

Can I upgrade the CPU, memory, bandwidth, disk, and other configurations of a CVM
instance enabled by a custom image?
Yes. You can upgrade all of them. For more information, see Change Instance Configuration and Adjust Network
Configuration.

Can a custom image be used across regions?
No. A custom image can only be used in the same region. For example, you cannot directly launch a CVM instance in
East China (Nanjing) using the custom image created from a CVM instance in East China (Shanghai).
To use a custom image across regions, copy the image to the target region first. For more information, see Copying
Images.

Where can I view the image creation progress? How long does it take to create an image?
You can view the image creation progress on the Images page of the CVM Console. The time it takes to create animage depends on the size of the instance’s data.

©2013-2022 Tencent Cloud. All rights reserved.

Page 48 of 131

Cloud Virtual Machine

Copying Images：

Last updated 2024-01-06 17:26:45

Under what circumstances do I need to copy an image?
Custom images can only be used in the same region. You can perform the following operations by copying images:
Deploy applications on the CVM instance in multiple regions.
Migrate the CVM instance to other regions.
Use custom images across regions.

Which images can I copy?
You can only copy custom images and cannot copy public images, service marketplace images, and images that
others have shared with you.

Which regions currently support copying images?
All Tencent Cloud regions support copying images.

How long does it take to copy an image?
It depends on the network transmission speed and the task waiting queue length. To copy an image, you need totransfer the image files from a region’s availability zone to the target region’s availability zone via the network. Pleasewait patiently.

How much does it cost to copy an image？

Copying images across regions is free for now, but the copied image will occupy the snapshot capacity and incur acost. For more information, see Pricing List.

How do I copy the image resources under my account to other regions under another
Tencent Cloud account?
You need to first copy your image to the target region, and then share the image under the target region with another
Tencent Cloud account. After the image is shared, it will appear in the target account’s shared image list.

Is there a capacity limit for copying images?
No.

©2013-2022 Tencent Cloud. All rights reserved.

Page 49 of 131

Cloud Virtual Machine

Issues on Custom Image：

Last updated 2024-05-16 10:19:57

What is the maximum number of users an image can be shared with?
500 users.

Can the name and description of a shared image be changed?
No.

Does a shared image count toward my image quota?
No.

Are there any region limitations for a shared image on creating and reinstalling a CVM
instance?
Yes. The shared image should be in the same region as the source image. The CVM instance can only be created andreinstalled in the same region.

Can a shared image be copied to other regions?
No.

Can a custom image that has been shared with other users be deleted?
Yes, but you need to cancel all sharing for this custom image first.

Can an image shared by other users be deleted?
No.

What are the risks of using a custom image shared by other users?
Tencent Cloud does not guarantee the integrity and security of images shared by other users. Please select images
shared by a trusted account.

Can I share with others an image another user shared with me?
No.

What are the risks of sharing a custom image with another account?
Data and software leakage may occur. Before sharing a custom image with another account, make sure the image
has no sensitive data or software. Be aware that the account you share the image with can create CVM instances fromthe shared image to create more custom images. The constant transfer of data will increase the risk of leakage.

©2013-2022 Tencent Cloud. All rights reserved.

Page 50 of 131

Cloud Virtual Machine

Can I create an instance using an image that I shared with other users?
Yes. You can create a CVM instance using the image you shared with another account. You can also create a custom
image based on the CVM instance.

Can an image created on Server A in North China be shared with Server B in East China?
If both servers are under the same account, you can directly copy the image to Server B in East China. For detailed
directions, see Copying Images.
If both servers are under different accounts, you need to copy the image to the East China region and then share itwith the account of Server B. For detailed directions, see Copying Images, Sharing Custom Images, and Cancelling
Image Sharing.

©2013-2022 Tencent Cloud. All rights reserved.

Page 51 of 131

Cloud Virtual Machine

Changing Images (Reinstalling System)：

Last updated 2024-01-06 17:26:45

Does CVM support reinstalling the operating system?
Reinstalling the operation system is an important method to restore instances to their initial status in the event of asystem failure. For more information, see Reinstalling System.

How long does it take to reinstall the operating system for an instance?
Reinstallation generally takes 10-30 minutes.

What should I do if re-installation is very slow or fails?
Reinstallation generally takes 10-30 minutes.
If it has been less than 30 minutes, please continue to wait.
If reinstallation does not complete within 30 minutes or fails, contact us by submitting a ticket.

Will reinstalling the operating system cause data loss?
After reinstallation, all data on the server’s system disk will be cleared and the system disk will be restored to its initial
status. All data on the server’s data disk will be retained but cannot be used until the data disk is mounted manually.

How can I replace the operating system of a CVM with an existing image?
See Reinstalling System.

©2013-2022 Tencent Cloud. All rights reserved.

Page 52 of 131

Cloud Virtual Machine

Cloud-Init & Cloudbase-Init：

Last updated 2024-03-26 10:28:49

Cloud-init
What is cloud-init?
Cloud-init is an open source tool that runs inside a CVM instance as a non-resident service. It is executed at startup
and exits immediately after execution. It does not listen to any ports.
All the Linux public images of Tencent Cloud are pre-installed with the cloud-init service. You need to run the service
as the root user because the service is mainly used for the initialization of CVM instances such as configuring DNS,
hostname, and IP, and the execution of some custom scripts that users specify to be executed during the first bootwhen creating the CVM instances.

How do I check whether the cloud-init service inside a Linux instance is working properly?
Troubleshooting cloud-init service errors
Log in to a Linux instance using the standard login method (recommended). Then, run the following commands insequence and observe whether an error is reported. If the execution result is displayed, the service is runningnormally. Otherwise, the cause of the error will be reported. You can troubleshoot the error accordingly.
Note:This step only applies to CVM instances created with public Linux images. If you installed cloud-init by yourself, adjust
the commands according to the actual situation.
1. Delete the cloud-init cache directory.

©2013-2022 Tencent Cloud. All rights reserved.

Page 53 of 131

Cloud Virtual Machinerm -rf /var/lib/cloud
2. Perform complete cloud-init initialization.

©2013-2022 Tencent Cloud. All rights reserved.

Page 54 of 131

Cloud Virtual Machine/usr/bin/cloud-init init --local
3. Pull data from the configured data source.

©2013-2022 Tencent Cloud. All rights reserved.

Page 55 of 131

Cloud Virtual Machine/usr/bin/cloud-init init
4. Cloud-init initialization involves multiple stages. To ensure sufficient dependencies between the stages, specify theconfig stage for the cloud-init modules.

©2013-2022 Tencent Cloud. All rights reserved.

Page 56 of 131

Cloud Virtual Machine/usr/bin/cloud-init modules --mode=config
5. Specify the final stage for the cloud-init modules.

©2013-2022 Tencent Cloud. All rights reserved.

Page 57 of 131

Cloud Virtual Machine/usr/bin/cloud-init modules --mode=final

What initialization operations does cloud-init perform on instances?
Tencent Cloud implements all instance initialization operations through cloud-init, ensuring the transparency of theoperations inside an instance. The following briefly covers some initialization operations. For more details, see cloudinit documentation.
Initialization
Type

Default Behavior©2013-2022 Tencent Cloud. All rights reserved.

Customization

Notes

Page 58 of 131

Cloud Virtual Machine

hostname

During the first launch of

If you create or reinstall an

If preserve_hostname isinitialization

an instance, cloud-init sets

instance with a custom image

scripts-user is disabled, th

the hostname of theinstance according to theand you want to keep thecustom `hostname` settings of/var/lib/cloud/instanceinside the instance will not be exe

hostname information in
vendor_data.json .

the image, you can set
preserve_hostname inconfiguration will also affect the in
sub-items such as the installation/etc/cloud/cloud.cfg

Observability Platform and cloud

to true and delete -software source settings. Also, th
not be executed when you create

scripts-user

beforecreating the custom image.

/etc/hosts
initialization

If you create or reinstall an

After you disable - scripts-

instance with a custom image
and you want to keep theinitialization script

custom `/etc/hosts` settings ofthe image, of the image, you

inside the instance will not be exe
configuration will also affect the in
sub-items such as the installation

initializes /etc/hosts

can delete the following
configuration fromto 127.0.0.1/etc/cloud/cloud.cfg$hostname by default.

before creating the custom

During the first launch of
an instance, cloud-init/var/lib/cloud/instanceObservability Platform and cloud
software source settings. Also, th

image: - scripts-user

not be executed when you create
During instance restart,
the

and

settings of some existing instanc-['update_etc_hosts','once-per-instance'] .

For information about the solution
etc/hosts Configuration of Linux I

If you create or reinstall an
instance with a custom image
During the first launch of
DNS
initialization(non-DHCP
scenario)an instance, cloud-init sets
the DNS of the instanceaccording to thenameservers informationinvendor_data.json .

and you want to keep thecustom DNS settings of theimage, you can delete thefollowing configuration from/etc/cloud/cloud.cfg

None.

before creating the custom
image: - resolv_conf
andunverified_modules:['resolv_conf'] .

SoftwareDuring the first launch of

If you create or reinstall ansourceinitialization

an instance, cloud-init sets
the software source of theinstance with a custom image
and you want to keep the

instance according to thecustom software source

write_files information in
vendor_data.json.

settings of the image, you candelete the following

None.

configuration from©2013-2022 Tencent Cloud. All rights reserved.

Page 59 of 131

Cloud Virtual Machine/etc/cloud/cloud.cfg
before creating the custom
image: - write-files .

NTPinitialization

During the first launch of

If you create or reinstall an

an instance, cloud-init
sets the INTP server

instance with a custom image
and you want to keep theconfiguration of thecustom NTP settings of theinstance according to the
NTP Server information inimage, you can delete thefollowing configuration fromvendor_data.json/etc/cloud/cloud.cfg

and starts the NTP
service.

before creating the custom
image: - ntp .

None.

If you create or reinstall an
instance with a custom image
During the firstlaunch of an instance,
Password
initialization

cloud-init sets the default
account password of theand you want to keep thecustom default accountpassword of the image, you
can delete the following

instance according to thechpasswd information in

configuration fromvendor_data.json .

before creating the custom

None.

/etc/cloud/cloud.cfg
image: - setpasswords .
If you create or reinstall an

Key binding

During the first launch of
an instance, cloud-init sets

instance with a custom image
and you want to keep thethe default account key ofthe instance according tocustom key of the image, you
can delete the following

the `ssh_authorized_keys`

configuration frominformation in
vendor_data.json .

/etc/cloud/cloud.cfg

If you manually bind the instanceinstance, the previous key will be
perform the key binding operatio

before creating the custom
image: - users-groups .

NetworkDuring the first launch of

If you create or reinstall an

initialization(non-DHCP

an instance, cloud-init sets
the IP, Gateway, andinstance with a custom image
and you want to keep the

scenario)

Mask of the instancecustom network information ofaccording to theinformation in

the image, you can add thefollowing configuration to

network_data.json .

/etc/cloud/cloud.cfg

None.

before creating the custom©2013-2022 Tencent Cloud. All rights reserved.

Page 60 of 131

Cloud Virtual Machine

image: network:{config: disabled} .

How can I fix common issues related to Cloud-Init?
1. Error due to the unmounting of Cloud-Init dependencies
Problem description:
When commands are used to check whether the Cloud-Init service is working properly, the following error is returned:©2013-2022 Tencent Cloud. All rights reserved.

Page 61 of 131

Cloud Virtual Machine

Traceback (most recent call last):
File "/usr/bin/cloud-init", line 5, in********
raise DistributionNotFound(req)pkg_resources.DistributionNotFound: pyyaml
Problem analysis:“pkg_resources.DistributionNotFound: xxxxx” indicates that the cloud-init dependencies have been uninstalled.
Solution:
1.1 Reinstall the dependencies.
1.2 Follow Troubleshooting cloud-init service errors to see if the error is returned again.
2. Error due to the modification of the default Python interpreter
Problem description:
An error is returned when cloud-init is run on startup.
Problem analysis:
When cloud-init is installed, Python 2 is used as the default Python interpreter, which means that symbolic links,/usr/bin/python and /bin/python , are linked to Python 2. Users may change the default Pythoninterpreter to Python 3 inside the instance by directing the symbolic links, /usr/bin/python and/bin/python , to Python 3. Due to compatibility issues, an error will be returned when cloud-init is run on startup.
Solution:
1.1 Taking Python 2.7 for example, modify the Python interpreter specified in the /usr/bin/cloud-init file bychanging #!/usr/bin/python or #!/bin/python to #!/usr/bin/python2.7 .
Note:
Do not use symbolic links. Point directly to a specific interpreter.
1.2 Follow Troubleshooting cloud-init service errors to see if the error is returned again.

Cloudbase-Init
What is Cloudbase-Init?
Like cloud-init, Cloudbase-Init is a bridge by which you can communicate with Windows CVM instances. The
Cloudbase-Init service is run when an instance boots up for the first time. The service will read the configuration
information of the instance and initialize it. Following operations such as resetting password and modifying IP
addresses are also done via Cloudbase-Init.

How do I check whether the Cloudbase-Init service inside a Windows instance is working
properly?

©2013-2022 Tencent Cloud. All rights reserved.

Page 62 of 131

Cloud Virtual Machine

Troubleshooting Cloudbase-Init service errors
1. Log in to the instance.
Note:
If you forget your password or fail to reset your password because of Cloudbase-Init service exceptions, you can reset
your password by following Step 2.
2. ﻿
Choose Control panel > Administrative tools > Services.
3. Find the Cloudbase-Init service, right-click it, and go to Properties.
View Startup type and make sure it is set to Automatic, as shown in the figure below:

View Log on as and make sure that Local System account is selected, as shown in the figure below:©2013-2022 Tencent Cloud. All rights reserved.

Page 63 of 131

Cloud Virtual Machine

Manually start the Cloudbase-Init service and see if any error is returned.
If any error is returned, you need to fix the issue first and check whether you have installed any security software which
may stop Cloudbase-Init from performing related operations.

©2013-2022 Tencent Cloud. All rights reserved.

Page 64 of 131

Cloud Virtual Machine

Open the registry, find each LocalScriptsPlugin, and make sure its value is 2, as shown in the figure below:©2013-2022 Tencent Cloud. All rights reserved.

Page 65 of 131

Cloud Virtual Machine

Check whether CD-ROM loading is disabled. If there is an optical disc drive as shown in the figure below, the loading
has not been disabled. Otherwise, you need to enable the loading.

©2013-2022 Tencent Cloud. All rights reserved.

Page 66 of 131

Cloud Virtual Machine

How do I view Cloudbase-Init execution logs?
You can view the log files for different operating systems:
Linux: /var/log/cloud-init-output.log
Windows: C:\\Program Files\\Cloudbase Solutions\\Cloudbase-Init\\log\\cloudbaseinit.log

How do I fix common issues related to Cloudbase-Init?
Failed to reset password during initialization
Possible reasons:
The Cloudbase-Init account password is manually changed, which results in the failure to start the Cloudbase-Init
service, which further led to the failure of operations such as resetting password during initialization.

©2013-2022 Tencent Cloud. All rights reserved.

Page 67 of 131

Cloud Virtual Machine

The Cloudbase-Init service is disabled, which led to the failure of operations such as resetting password duringinitialization.
The security software installed stops the Cloudbase-Init service from resetting password so that the operation returns
a successful result but actually failed.
Solution:
Follow the corresponding solution to each possible reason to fix the issue.
1.1 Change the Cloudbase-Init service to LocalSystem service. For details, see step 2 in Checking the operation of the
Cloudbase-Init service.
1.2 Change the startup type of the Cloudbase-Init service to automatic. For details, see step 2 in Checking theoperation of the Cloudbase-Init service.
1.3 Uninstall the security software involved or add the relevant operations of the Cloudbase-Init service to the white listof the security software.

©2013-2022 Tencent Cloud. All rights reserved.

Page 68 of 131

Cloud Virtual Machine

FAQs about Red Hat Enterprise Linux Image：

Last updated 2024-03-28 10:28:31

Which Red Hat Enterprise Linux image tags are available? Which models support Which Red
Hat Enterprise Linux?
Note:
To use Red Hat Enterprise Linux images, select an instance type that is verified by Red Hat Enterprise Linux when
you purchase the CVM.
Instance specifications

RHEL 7 Series

RHEL 8 Series

RHEL 9 Series

Standard SA5

Not supporte

Supported

Supported

Standard SA3, S6, SA2, S5

Supported

Supported

Supported

MEM optimized M6, M5

Supported

Supported

Supported

Computing C4, C3

Supported

Supported

Supported

Why can't I see the Red Hat Enterprise Linux image when purchasing certain types of
instances?
Please check if your selected instance model is the one listed in the table above.

What should I do if my existing image tag or model doesn't meet the requirements?
You can submit a ticket to contact us.

How is the Red Hat Enterprise Linux image billed?
For billing details, see Billing Description.

After-sales support
Free source updates (including version updates and vulnerability patches) are available to the officially licensed Red
Hat Enterprise Linux OS sold on Tencent Cloud official website. If you have any problems during use, please submit aticket.

Are refunds supported after I purchased the Red Hat Enterprise Linux image?
The Red Hat Enterprise Linux images are licensed through official authorization from Red Hat. Once a license has
been purchased and activated on Tencent Cloud, it is not eligible for a refund.
For instances with a pay-as-you-go billing mode, those using Tencent Cloud authorized Red Hat Enterprise Linux
images can be terminated or returned.

©2013-2022 Tencent Cloud. All rights reserved.

Page 69 of 131

Cloud Virtual Machine

For instances with a monthly subscription billing mode, those using Tencent Cloud authorized Red Hat EnterpriseLinux images are not eligible for termination or refund. If you wish to receive a refund of the instance fee, you canreinstall the system with another open-source Linux operating system, such as CentOS, and then proceed with theregular refund process for the instance.

：

Note

After the system is reinstalled, the fee of the image will not be refunded.

How is the Red Hat Enterprise Linux image billed under the RI mode?
For details, see Billing Description - Red Hat Enterprise Linux Image.

Does the same discount apply to both the CVM instance and the Red Hat Enterprise Linux
image?
The discount available to the CVM instance is not applied to the Red Hat Enterprise Linux image. No other discounts
are available.

Can I use a voucher to purchase Red Hat Enterprise Linux images?
No. Vouchers cannot be used to purchase Hat Enterprise Linux images.

Does Tencent Cloud support BYOL for Red Hat Enterprise Linux images?
Yes. You can import a custom image to create an instance. No commercial image license fee occurs. For more
information, see Importing Images.

Can I change the configuration and the billing mode for an instance with Red Hat EnterpriseLinux OS?
No.

©2013-2022 Tencent Cloud. All rights reserved.

Page 70 of 131

Cloud Virtual Machine

Others：Last updated 2024-01-06 17:26:45

What is an image?
An image is the template for CVM software configuration (operating systems, pre-installed programs, etc.). Tencent
Cloud requires users to use images to launch instances. An image can launch multiple instances, and users can use it
repeatedly. For more information on images, please see Overview.

What do I need to do before importing the image?
Before importing an image, you need to complete two major steps: applying for permissions and preparing image files.
For more information, please see Overview.

How do I export an image for local testing?
Tencent Cloud Service Migration supports images in qcow2, vhd, raw, and vmdk formats.
You can use the image export tools of virtualization platforms such as VMWare vCenter Convert or Citrix XenConvert.
For more information, please reference each platform’s export tool documentation. You can also export images using
Disk2vhd (Windows) or by running commands (Linux).

Can I delete a custom image that has been used to create a CVM instance?
Yes. After a custom image is deleted, it can no longer be used to launch a new CVM instance. It will not affectinstances that have already been launched. If you want to delete all instances launched from this image, see
Reclaiming Instances or Terminating Instances.

Can I delete a custom image that has been shared with another account?
No. You cannot delete a custom image that has been shared with another account. To delete it, you need to cancel
image sharing first. For more information, see Cancelling Image Sharing.

©2013-2022 Tencent Cloud. All rights reserved.

Page 71 of 131

Cloud Virtual Machine

Service Migration：

Last updated 2024-03-26 10:29:23

Offline Migration
Why do COS upload and migration take so long?
The time it takes to upload images to COS is related to the image file size and bandwidth. We recommend you use
compressed image formats (QCOW2 or VHD) to shorten the transmission and migration time.

Why did the migration task fail?
Tencent Cloud's service migration supports images in QCOW2, VHD, VMDK and RAW formats. Make sure that yourimage is in one of these formats.
Make sure that your image file has been uploaded to COS, check COS permissions, and check that the temporary
URL is valid and that the file is not corrupted.
Make sure that the target CVM or cloud disk are not expired.

How do I troubleshoot the error occurred in a migration task?
Failed to obtain the metadata of the image file: The image file is damaged or the image file format is notsupported. Supported image file format: QCOW2, VHD, VMDK, and RAW.
Image decompression failed: Image creation error. Check the image package and export the image again. Make
sure that the destination disk has a larger capacity than the source disk.
The storage space of the target device is too small: The capacity of the system disk or data disk you want tomigrate to is smaller than the capacity of the source disk or the size of the image file.
Failed to access the COS image file: Not authorized to access COS. Make sure the COS file is in the current
region, COS permission is assigned and the temporary URL is valid.
Failed to migrate to the destination disk:
The destination disk does not have enough capacity.
An error occurred during the image creation.
Task timeout, System error, and Other reasons: Try again. If the problem persists, contact us.

What should I do if the network is disconnected after the offline migration of the Windows
server?
You can reset the Windows network configuration as instructed below. For more information, see Ping Failures.
1. For VPCs created before June 2018, check if the server supports DHCP. If not, check the static IP.
2. If the server supports dhcp, check if the assigned private IP is correct. If it is incorrect, run the command as theadmin without restarting the server: ipconfig /release; ipconfig /renew .

©2013-2022 Tencent Cloud. All rights reserved.

Page 72 of 131

Cloud Virtual Machine

3. If the assigned IP is correct, but the network is disconnected, run ncpa.cpl to open the local connection, and disableand enable the ENI.
4. Run the command as the admin and restart the server: reg delete"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows
NT\\CurrentVersion\\NetworkList\\Profiles"/f .

Online Migration
Which types of operating systems and disks are supported by online migration?
Mainstream Linux and Windows operating systems are supported.
Migration is irrelevant to disk type and usage.

What is the difference between online migration and image import?
Both can migrate source systems to Tencent Cloud. However, online migration allows you to transfer the system anddata from the source server to Tencent Cloud without manually preparing, exporting and importing an image.

Will the public IP of the source server be migrated?
No. The online migration only syncs the source system and data, rather than the public IP.

Does the online migration tool support checkpoint restart?
Yes. You can run the tool again to resume the transfer after an interruption.

Do I need to retain the tool after migration is completed?
No. Once migration is completed, you can directly delete the tool on the source server.

What about migration speed and cost?
Speed: The speed is subject to the destination CVM instance bandwidth. In the test where a 1CIG pay-as-you-go
instance with a bandwidth of 12 Mbps is used, the actual migration speed is about 9 Mbps. For the specific calculation
method, see Migration Time Estimation.
Cost: The migration tool is free of charge. You will be charged for bandwidth and other resources used during
migration. They will be billed by traffic and duration.

Can I migrate multiple CVMs at the same time?
Yes. You can migrate multiple CVMs to different destination CVMs simultaneously.

How do I check and install Virtio?
Check and install Virtio by referring to Checking Virtio Drivers in Linux.

©2013-2022 Tencent Cloud. All rights reserved.

Page 73 of 131

Cloud Virtual Machine

How do I install Rsync?
Select one of the following commands based on the operating system of the source server to install Rsync:
CentOS: yum -y install rsync： apt-get -y install rsync

UbuntuSUSE: zypper install rsync
For the specific commands of other Linux distributions, see the installation document at the corresponding official
website.

How do I disable SELinux?
Edit the /etc/selinux/config file and set SELINUX=disabled .

FAQs about Console-Based Online Migration
Where can I download the online migration tool?
Click here to download the online migration tool package and use it as instructed in Migration in Console.

How do I import a migration source?
1. Download and decompress online migration tool package.
2. Run the executable file for the source server architecture to import the migration source to the online migration pagein the CVM console.
If the source server is 32-bit, run go2tencentcloud_x32 .
If the source server is 64-bit, run go2tencentcloud_x64 .

How do I update a migration source or import a migration source again?
If information such as migration source disk changes, you need to update the migration source information or import
the source again. Delete the existing migration source first and then run the client to import the source again.

How do I delete a migration source?
Log in to the CVM console, go to the online migration page, and click Delete on the right of the target migration
source. If your migration source is associated with a migration task that has not been completed, pause and delete thetask first and then delete the source.

How do I select the destination CVM instance before migration?
We recommend you use the same operating system for the source server and destination CVM instance. For
example, to migrate a CentOS 7 source server, select a CentOS 7 CVM as the destination.

Which migration task status indicates that the task has been completed?

©2013-2022 Tencent Cloud. All rights reserved.

Page 74 of 131

Cloud Virtual Machine

A migration task has been completed only when it is in the Successful status; otherwise, it has not been completed.

How do I delete a migration task?
Perform the following operations based on the actual migration task status:
When a migration task is in the Not started or Successful status, you can click Delete on the right to directly deleteit.
When a migration task is in the Failed status, to delete it, you need to keep the migration source online and click
Delete on the right. Then the task will enter the Deleting status, and the migration tool will automatically clear the
resources generated by the migration task and delete the task.

How do I cancel a migration task if it takes too long?
In this case, log in to the CVM console, go to the online migration page, pause the migration task, and click Delete on
the right to delete it.

What should I do if the relay instance is terminated?
During migration to the destination Tencent Cloud image, if the created relay instance is terminated by mistake, you
can delete the current migration task and create and start a migration task for the migration source again.

What should I do if an error or failure occurred during migration in the console?
Check the common errors below:
During migration to the destination CVM instance, ports 80 and 443 are not open in the security group of thedestination CVM instance.
Solution: modify the security group rules of the destination CVM instance to open ports 80 and 443.
During migration to the destination CVM instance, the disk capacity of the destination CVM instance is insufficient.
Solution: Select a CVM instance with a sufficient capacity, mount a disk with a sufficient capacity to it, and create amigration task again to start migration.
An error occurred when you create a relay instance during migration to the destination Tencent Cloud image; forexample, a log error message Failed create transit instance, maybe no available source in target region isdisplayed.
Solution: there are no available resources in the destination region of the migration task. In this case, you can selectanother region or migrate the server to the specified CVM instance.
If the problem persists or the reason is not identified, contact us and provide the migration log file (in the log
directory of the migration tool by default).

What can I get after migration?
After a migration task is completed, a Tencent Cloud resource is generated according to your specified destination
type.

©2013-2022 Tencent Cloud. All rights reserved.

Page 75 of 131

Cloud Virtual Machine

Migrate to a CVM image: A destination Tencent Cloud image will be generated for the migration source after
migration. You can click the CVM image ID in the row of the migration task to view the image details on the CVM
image page, and use the image to quickly create CVM instances. After a CVM image is created successfully, a CVM
snapshot associated with it will be created at the same time.
Migrate to a CVM instance: The migration source will be migrated to the destination CVM instance after migration.

How do I check the system after migrating a Linux server?
Check whether the target CVM instance starts up normally, whether data on the target CVM instance is consistent
with that on the source server, and whether the network and other system services are normal.

How do I migrate a source again after migration is completed?
Log in to the CVM console, and create and start a migration task for the migration source again.

What should I do if the network is disconnected after the online migration of the Windows
server?
You can reset the Windows network configuration as instructed below. For more information, see Ping Failures.
1. Check if the server supports dhcp (all VPCs created after June 2018 support dhcp). If not, check if the static IP iscorrect.
2. If the server supports dhcp, check if the assigned private IP is correct. If it is incorrect, run the command as theadmin without restarting the server: ipconfig /release; ipconfig /renew .
3. If the assigned IP is correct, but the network is disconnected, run ncpa.cpl to open the local connection, and disableand enable the ENI.
4. Run the command as the admin and restart the server: reg delete"HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows
NT\\CurrentVersion\\NetworkList\\Profiles"/f .

Online Migration Tool
Where can I download the online migration tool?
Click here to download the compressed migration tool package and use it as instructed in Online Migration Tool.

How do I use the online migration tool?
You need to download the tool and upload it to the source server and modify the configuration file based on the actual
server conditions before running it. To perform batch migration, you can write a script to implement batch processing.

What should I do if an error or failure occurred during migration with the tool?
Check the common errors below:©2013-2022 Tencent Cloud. All rights reserved.

Page 76 of 131

Cloud Virtual Machine

Ports 80 and 443 are not open in the security group of the destination CVM instance.
The DataDisks field in the user.json file is not configured for migrating the data disk of the source server.
The system disk capacity of the destination CVM instance is insufficient to store all the data.
In the private network migration mode, the migration stage 3 is not implemented, which causes the destination CVM toexit the migration mode.
If the problem persists or the reason is not identified, contact us and provide the migration log file (in the log
directory of the migration tool by default).

©2013-2022 Tencent Cloud. All rights reserved.

Page 77 of 131

Cloud Virtual Machine

Network
IP Address：

Last updated 2024-01-06 17:26:45

Public IP
How can a CVM without public IP access public network?
If you did not purchase the public IP when purchasing the CVM or have returned the public IP, you can apply for an
EIP on the EIP Console and bind it to your CVM to allow public network access.

Can I change my public IP?
You can change the public IP of your CVM. For more information on specific operations, please see Changing
Instance Public IP.

How do I keep a public IP unchanged?
If you need to retain a specific public IP under your account, you can convert it to an EIP, which can be bound to thedevice and used to access the public network. This EIP will be retained under your account until you release it.
For more information on the related operations, see EIP.

What is a public IP address?
A public IP address is an unreserved IP address on the Internet. A CVM with a public IP address can be accessible toand by other computers on the Internet.
For more information, see Internet Access.

How do I obtain the public IP address of an instance?
For details, see Getting Public IP Addresses.

How do I change the public IP address of an instance?
For details, see Changing Instance Public IP.

What are the differences between public gateways and CVMs with public IP addresses?
Public gateways enable the public network traffic forwarding feature in the image. However, CVMs with public IP
addresses do not have this feature by default. Therefore, CVMs created on Windows public image cannot function as
public gateways because the Windows image has no traffic forwarding feature.

Why can’t I change the public IP of my CVM?

©2013-2022 Tencent Cloud. All rights reserved.

Page 78 of 131

Cloud Virtual Machine

Possible reasons include:
The CVM instance is shut down and incurs no charges when shut down.
The public IP of the CVM has been changed.

How can I obtain the public IP address of an instance that has no public IP (IPv4) assigned
during the instance creation?
You can obtain the public IP of an instance by applying and binding an EIP to it. For the step-by-step operations, see
EIP.

Private IP
What is a private IP address?
A private IP address cannot be accessed through the Internet. That is how Tencent Cloud provides private network
services.
For more information, please see Private Network Access.

How do I obtain the private IP address of an instance?
For details, see Getting Private IP Addresses and Setting DNS.

Can I change the private IP address of an instance in addition to its public IP address?
Yes, you can change the private IP of an instance. For operations, see Modifying Private IP Addresses.

©2013-2022 Tencent Cloud. All rights reserved.

Page 79 of 131

Cloud Virtual Machine

Elastic Public IP issues：

Last updated 2024-01-06 17:26:45

What are EIPs used for?
ElPs are applicable to the following scenarios:
Disaster recovery. We strongly recommend you use EIPs for disaster recovery. For example, when one of your servers
fails, you can unbind the EIP from this server and then bind it to a healthy server to quickly resume services.
Retaining a specific public IP. If you need to retain a specific public IP under your account, you can convert it to an
EIP, which can be bound with or unbound from the device and used to access the public network. This EIP will be
retained under your account until you "release" it.
Other special cases. When you need to change an IP in some cases, you can convert the public IP to an EIP and thenbind the EIP to or unbind from your device. But the EIP resource under an account is limited in each region, pleaseplan and use EIPs accordingly.

How is an EIP billed?
1. The fee displayed on the console applies to EIPs that have been idle for more than 1 hour. EIPs can be billedaccurately to seconds. EIPs that have been bound/unbound multiple times are billed based on the total duration (insec) for which they are unbound.
2. EIPs that have been idle for less than 1 hour are billed for resource occupation fee on a pro rata basis.

When is an EIP billed?
You can apply for, bind, unbind or release EIPs. With limited EIP resources available, an EIP is billed for a small
resource occupation fee only when it is unbound.

How do I stop EIP billing?
When you no longer need an EIP, you can release it to stop the billing.
For more information on the specific operations, see Releasing EIPs.
If you need to retain an EIP but want to stop the billing, bind it to a device (such as CVM or NAT). A bound EIP will not
be billed.

Can an EIP be converted back to a public IP?
An EIP cannot be converted back to a public IP.

Can an EIP be retrieved?
You can retrieve public IPs that have not been assigned to other users. For details, see Retrieving the Public IP
Address.

©2013-2022 Tencent Cloud. All rights reserved.

Page 80 of 131

Cloud Virtual Machine

Elastic Network Interface：

Last updated 2024-01-06 17:26:45

What is ENI?
Elastic Network Interface (ENI) is an elastic network interface bound to CVMs in a VPC, which can be migrated
among multiple CVMs. ENI is very useful for configuring management networks and establishing highly reliablenetwork solutions.
ENI has VPC, availability zone and subnet attributes. You can only bind it to CVMs under the same availability zone. A
CVM can be bound with multiple ENIs, and the maximum number allowed varies by CVM specifications.

What are the restrictions to use ENIs on CVMs?
For details, please see use limits section in Use Limits Overview.

What is the basic information of an ENI?
Please see Concepts in Elastic Network Interface (ENI).

How do I create an ENI?
Please see Creating an ENI.

How do I view the ENI information?
Please see Viewing ENI Information.

How do I bind an ENI to a CVM instance?
Please see Binding and Configuring CVMs.

How do I configure an ENI in the CVM instance?
Please see Binding and Configuring CVMs.

How do I modify or customize the private IP of an ENI?
CVMs in VPC support modifying and customizing the private IP of an ENI. Follow the steps below:
1. Log in to VPC Console.
2. In the left side bar, click IP and Interface > ENI to enter the ENI list page.
3. Click the ID/Name of an ENI to enter its details page to view its information.
4. Select the IPv4 address management tab and click Assign Private IP.
5. In the pop-up window, select the IP assigning method as Enter manually to enter the IP address you want tomodify.
6. Click OK to complete the operation.

©2013-2022 Tencent Cloud. All rights reserved.

Page 81 of 131

Cloud Virtual Machine

After the modification is made on the console, you also need to modify the configuration file of the ENI. For more
information, please see Binding and Configuring CVMs.

©2013-2022 Tencent Cloud. All rights reserved.

Page 82 of 131

Cloud Virtual Machine

Public Network Bandwidth：

Last updated 2024-01-06 17:26:45

What do the inbound bandwidth and the outbound bandwidth for CVM instances mean?
Inbound bandwidth: a bandwidth that flows into CVM instances. For example, the bandwidth resulting fromdownloading external network resources on the CVM instance.
Outbound bandwidth: a bandwidth that flows out of CVM instances. For example, the bandwidth resulting fromexternal access from the CVM instance.

How is the public network bandwidth billed for CVM instances?
For more information, see Public Network Billing.

The bandwidth cap for pay-as-you-go instances using the bill-by-traffic billing mode is 200
Mbit/s. How do I increase the bandwidth cap?
The public network bandwidth cap depends on the billing modes and the configurations of CVM instances. For more
information, see Public Network Bandwidth Cap.

©2013-2022 Tencent Cloud. All rights reserved.

Page 83 of 131

Cloud Virtual Machine

Network：

Last updated 2024-01-06 17:26:45

There is no network connection after I log in to the CVM. How do I solve this problem?
If there is no network access (for example, the webpage is inaccessible) after you log in to the CVM, you need tocheck the DNS configuration. Set the CVM to obtain the DNS address automatically by following the instructions
below.
Note:
The following operations take Windows Server 2012 as an example.
1. Log in to the Windows CVM.
2. On the desktop, click

and select Control panel -> Network and Internet -> View network status and tasks -> Change adapter
settings.
3. Right-click Ethernet and select Properties to open the “Ethernet Properties” window.
4. In the “Ethernet Properties” window, double-click and open the Internet Protocol Version 4 (TCP/IPv4)
Properties window.
5. In the Internet Protocol Version 4 (TCP/IPv4) Properties window, select Obtain an IP address
automatically and Obtain DNS server address automatically, and click OK, as shown below:©2013-2022 Tencent Cloud. All rights reserved.

Page 84 of 131

Cloud Virtual Machine

Can a VPC instance interconnect with the classic network instance?
Yes, but it has the following restriction:
The VPC IP address range (CIDR) must be 10.0.0.0/16 - 10.0.47.0/16 (including subsets). Otherwise, there will beconflicts.
Directions
Log in to the VPC Console, click the VPC ID/name to access its details page, and then click the Classiclink tab toassociate the classic network CVM to be interconnected.

How do I view classic network CVMs that are interconnected with VPC CVMs?
Log in to the VPC Console, click the VPC ID/name to access its details page, and view classic network CVMs
interconnected with VPC CVMs in Classiclink.

Can the CVM be switched to an overseas network?
After being purchased, the network cannot be changed for CVM. If you need an overseas network, we recommendthat you return the CVM and purchase an overseas CVM.

©2013-2022 Tencent Cloud. All rights reserved.

Page 85 of 131

Cloud Virtual Machine

How do I configure a private network DNS?
Please see Private Network Access.

Within the same IP range, the VPN can obtain the IP address of an IP range but cannot
access the internet. How do I solve this problem?
Please check that the following configurations are correct:
1. Are the manually added IP and the automatically obtained IP in the same IP subnet? Are the subnet masks thesame? Is the default gateway configured? Is the default gateway address correct?
2. Is DNS configured and is the DNS address correct?
3. If all of the configurations above are correct, check if the statically configured IP address has an IP conflict.
If none of the above works, please submit a ticket to contact us.

How do I add CVMs under accounts A and B to the same subnet?
By default, accounts are not interconnected by network. To interconnect accounts, see Creating Cross-accountPeering Connection or Network Instance Interconnection Crossing Account.

©2013-2022 Tencent Cloud. All rights reserved.

Page 86 of 131

Cloud Virtual Machine

Security
Passwords：

Last updated 2024-01-06 17:26:45

How can I obtain the initial CVM password?
If you purchase the CVM through Custom Configuration, you can obtain the initial password based on different login
methods as follows:
Login Method

Description

RandomPassword

The initial password will be sent to you via email and Message Center on the console.

SSH Key Pair

Disabled by default you can log in to the CVM using your username and password, but theinitial password will still be sent to you via email and Message Center on the console.

CustomPassword

The password you set is the initial password.

For more information, see Managing Login Password.

What should I do if I cannot receive the initial password via Message Center?
When you purchase a CVM, the initial password will be sent to you via email and Message Center on the console.
If you cannot find the password in Message Center, please confirm that you log in to the console with a root account. If
not, switch to the root account and check again.

What should I do if I forget my password?
You can reset the password. For more information, see Resetting Instance Password.

How do I change or reset the CVM password?
To reset the password of your CVM, see Resetting Instance Password.

What should I do if I fail to reset the password?
For Windows CVM, see Failed to Reset the CVM Password or the CVM Password Is Invalid to troubleshoot the issue.
For Linux CVM, please submit a ticket.

How do I reset CVM passwords in batches?
To reset CVM passwords in batches, see Resetting Instance Password.

©2013-2022 Tencent Cloud. All rights reserved.

Page 87 of 131

Cloud Virtual Machine

What are the default CVM login username and password?
The default username varies by operating systems:
For Windows instance, the default username is Administrator .
For Linux instance, the default username is root ( ubuntu for Ubuntu system).
The CVM password for remote login is set by you when you create the instance. For more information, see Creating
Instances. If you forgot the login password, you can reset it. For more information, see Resetting Instance Password.

©2013-2022 Tencent Cloud. All rights reserved.

Page 88 of 131

Cloud Virtual Machine

Password Login and SSH Key Login：

Last updated 2024-03-26 10:30:53

What is the difference between SSH key login and password login?
An SSH key allows you to log in to a Linux server remotely. It uses the key generator to create a key pair (public andprivate). The public key is added to the server, and the client can use the private key to complete the authenticationand login. Compared to password login, SSH key login is more secure and efficient.
Currently, Linux instance supports both password and SSH key login, while Windows instance only supports
password login. For related documentation, see:
Logging in to Linux Instance
Logging in to Windows Instance

I cannot use the password to log in to a Linux instance that is associated with an SSH key.
After the CVM is associated with an SSH key, password login is disabled by default. See Logging in to Linux
Instance (SSH Key).

Can I use SSH key together with the password login?
When you log in to Linux instance via SSH key, password login is disabled by default to improve security.

How do I create an SSH key and what if I lose it?
For more information on key creation, see Managing SSH keys.
If you lost the key, troubleshoot by the following methods:
Create a new key via SSH Key on the console and bind it with the original instance.
1.1 Create an SSH key.
1.2 After the key is successfully created, log in to the CVM Console.
1.3 Select the original instance with which you want to bind the key, click More -> Password/key -> Load a key.
You can then use the new key to log in to the instance.
Reset your password through the CVM Console and log in to the instance with your new password. For more
information, see Resetting Instance Password.

How do I bind/unbind an SSH key to or from the server?
For more information, see the Binding/Unbinding a key to or from a CVM section in Managing SSH keys.

How do I modify the SSH key name/description?
For more information, see the Modifying the SSH key name and description section in Managing SSH keys.

How do I delete an SSH key?

©2013-2022 Tencent Cloud. All rights reserved.

Page 89 of 131

Cloud Virtual Machine

For more information, see the Deleting SSH keys section in Managing SSH keys.

What are the use limits on SSH keys?
For more information, see the Use Limits section in SSH Keys.

How to troubleshoot if I fail to log in to a Linux instance using an SSH key?
For more information, see Unable to Log in to a Linux Instance via SSH.

I can not download my key.
The key can only be downloaded once. If you lost the key, we recommend that you create a new key, download andsave it.

How can I query which key is used by the CVM instance?
You can log in to the CVM Console and go to the instance details page to view keys used by the CVM.

©2013-2022 Tencent Cloud. All rights reserved.

Page 90 of 131

Cloud Virtual Machine

Security Groups：

Last updated 2024-01-06 17:26:45

Why does a security group have a reject rule by default?
Security group rules take effect in sequence from top to bottom. After a preceding allow rule is applied, other rules are
ignored by default. If all ports are open to the internet, the last deny rule does not take effect. We provide this default
configuration for security reasons.

How can I adjust the priority of a security group?
For more information, see Adjusting Security Group Priority.

If I bind an incorrect security group to an instance, what impact will this have on the
instance? How can I fix this problem?
Potential problems
You may fail to remotely connect to a Linux instance over SSH or a Windows instance via remote desktop.
You may fail to remotely ping the public IP and private IP addresses of the CVM instance in this security group.
You may fail to access over HTTP the web services exposed by the CVM instance in this security group.
The CVM instance in this security group may fail to access Internet services.
Solutions
If any of the aforementioned problems occur, you can go to Security Groups in the console and modify the security
group rule. For example, you can change the rule to "bind only all-ports-open security groups by default".
For more information on how to set a security group rule, see Security Groups.

What do the security group direction and policy mean?
The security group policies involve inbound and outbound directions. Outbound policies are used to filter outboundtraffic from the CVM, and inbound policies are used to filter inbound traffic to the CVM.
Security group policies are divided into those that allow and refuse traffic.

In which order do the security group policies take effect?
Security group policies take effect from top to bottom. When traffic passes through the security group, policy matchingis performed from top to bottom. A policy takes effect once matching is successful.

Why can an IP address that is rejected by a security group still access the CVM instance?
Possible reasons:
The CVM is bound to multiple security groups, and this IP address is allowed by another security group among them.
This IP address belongs to an approved Tencent Cloud public service.

©2013-2022 Tencent Cloud. All rights reserved.

Page 91 of 131

Cloud Virtual Machine

Can iptables be used along with security groups?
Yes, iptables and security groups can be used at the same time. Your traffic will be filtered twice as follows:
Outbound: processes in your instance > iptables > security groups.
Inbound: security groups > iptables > processes in your instance.

Why can't security groups be deleted even though all CVM instances have been returned?
Check whether there are still bound CVMs in the recycle bin. The security group cannot be deleted even if it is boundto a CVM in the recycle bin.

Can the name of a cloned security group be the same as that of a security group in thetarget region?
No. The name must be different from names of existing security groups in the target region.

Can a security group be cloned across different users?
No.

Can I clone a security group to another project or region using an API?
To facilitate the use of the console, we provide MC support but not cloud API support. You can use the cloud APIs forimporting and exporting security group rules in batches to clone security groups across projects and regions.

When I clone a security group across projects and regions, will CVM instances managed by
the security group also be copied?
No. Only the inbound and outbound rules of the security group are cloned. You need to associate CVMs again aftercloning.

What is a security group?
A security group is a virtual firewall that features stateful data packet filtering. It is used to configure the network
access control of CVM, Cloud Load Balancer, TencentDB, and other instances while controlling their outbound andinbound traffic. It is an important means of network security isolation.
Each CVM instance is bound to at least one security group, which must be specified when the instance is created.
CVM instances are interconnected in the same security group but cannot communicate with CVM instances acrosssecurity groups. However, you can authorize the interconnection between two security groups. For more information,see Security Groups.

Why do I need to choose a security group when creating CVM instances?
Before creating CVM instances, you must choose a security group to partition the security domains of the application
environment and authorize the security group rules to properly implement network security isolation.

©2013-2022 Tencent Cloud. All rights reserved.

Page 92 of 131

Cloud Virtual Machine

What should I do when I create CVM instances if I have not created a security group?
In this case, you can create a security group.
A security group supports the following rules. You can open IPs and ports as needed.
ICMP: opens to the ICMP protocol and allows the pinging of the server over the public network.
TCP:80: opens port 80 and allows access to Web services over HTTP.
TCP:22: opens port 22 and allows a remote connection to Linux CVMs over SSH.
TCP:443: opens port 443 and allows access to Web services over HTTPS.
TCP:3389: opens port 3389 and allows a remote connection to Windows CVMs over RDP.
Open the private network: opens to the private network and allows private network access among different cloud
resources (IPv4).

In what situations will the default security group rule be used to a security group?
The default security group rule will be used in the following situations:
When creating a CVM instance, if you select Quick Configuration to purchase the instance, the system willautomatically create a default security group for you, which will adopt the default security rule (i.e., allowing all IPv4
addresses).
However, for security reasons, we recommend you associate your CVM with a new security group that only opens
ports when absolutely necessary to avoid unnecessary security risks.
You can choose a template when creating a security group in the CVM console. Currently, supported templates
include Windows login, Linux login, Ping, HTTP(80) and HTTPS(443).

©2013-2022 Tencent Cloud. All rights reserved.

Page 93 of 131

Cloud Virtual Machine

Security Group Rules：

Last updated 2024-01-06 17:26:45

In what scenarios do I need to add security group rules?
To ensure the accessibility of CVM instances, you need to add security group rules in the following scenarios:
There is no security group rule (added or default) for CVM instances. If your CVM instances need to access the public
network or communicate with CVM instances associated to other security groups in the same region, you need to add
security rules.
The application you built uses a custom port or port range, instead of the default port. In this case, you need to open
the custom port or port range before testing the application connectivity. For example, if you set up an Nginx service
on your CVM instances that listens on the TCP 1800 communication port but your security group only opens port 80,
you need to add security group rules to ensure the accessibility of the Nginx service.
For other scenarios, see Security Group Use Cases.

What impact will incorrectly configuring security group rules have?
If any security group rule is configured incorrectly, CVM instances will fail to access other devices over the private
network or public network. For example:
You may fail to remotely connect to a Linux instance over SSH or a Windows instance via remote desktop.
You may fail to remotely ping the public IP of a CVM instance.
You may fail to access Web services provided by CVM instances over the HTTP or HTTPS protocol.
You may fail to access other CVM instances over the private network.

Are the inbound rules and outbound rules of a security group counted separately?
A maximum of 100 inbound and 100 outbound rules can be set for a security group.

Can I adjust the maximum number of security group rules allowed?
Each security group can configure up to 200 security group rules, including 100 inbound rules and 100 outboundrules. One CVM instance can be associated with up to 5 security groups and can therefore adopt up to 1,000 security
group rules, which is enough to meet the needs of most scenarios.
If your usage surpasses this upper limit, check whether redundant rules exist.
If so, remove them.
If not, create more security groups.
In addition, you can submit a ticket to raise the upper limit of security group rules.

©2013-2022 Tencent Cloud. All rights reserved.

Page 94 of 131

Cloud Virtual MachinePort：

Last updated 2024-01-06 17:26:45

Which ports should be opened to the Internet before I log in to an instance?
Generally, you need to open port 22 for a Linux instance, or port 3389 for a Windows instance. For more information
about ports applicable to other instance types, see Security Group Use Cases.

Which ports are often used in CVM?
For more information, see Server Common Port.

Why should a port be opened to the Internet? How can I open a specific port?
You can use the service only after you open the port to the Internet in the security group. For example:
If you want to access web pages using port 8080, the port must be enabled and opened to the Internet in the security
group.
To open a port to the Internet, follow the steps below:
1. Go to the security group page, and click the ID/name of the security group bound with this instance to go to its
details page.
2. Select Inbound/Outbound rule and click Add a Rule.
3. Enter your IP address (range) and port to be opened, and then select Allow to open the port.
For more information, see Adding Security Group Rules.

How can I change the default remote port of a CVM instance?
For more information, see Modifying the Default Remote Port of CVM.

Why cannot the service be used after I change the port?
After modifying the service port, you also need to open the corresponding port to the Internet in the security group.

Which ports are not supported by Tencent Cloud?
By default, TCP port 25 is blocked by Tencent Cloud. If you need to unblock this port, see Unblocking Port 25.
Some ports have security risks. Although these ports are not blocked by Tencent Cloud, they will be blocked by ISPs
and cannot be accessed. To avoid this, we recommend that you change ports and do not use the following ports forlistening:
ProtocolTCP
UDP

Blocked Port42, 135, 137, 138, 139, 445, 593, 1025, 1434, 1068, 3127, 3128, 3129, 3130, 4444, 5554, 5800,
5900, 9996
1026, 1027, 1434, 1068, 5554, 9996, 1028, 1433, 135 - 139©2013-2022 Tencent Cloud. All rights reserved.

Page 95 of 131

Cloud Virtual Machine

Why cannot I use TCP 25 port?
TCP port 25 is the default email service port. For security reasons, port 25 of CVM instances is blocked by default. If
you need to use it, see Unblocking Port 25.

©2013-2022 Tencent Cloud. All rights reserved.

Page 96 of 131

Cloud Virtual Machine

Firewall：Last updated 2024-05-29 15:50:55

How should I configure the firewall software iptables on a Linux OS?
Note:
iptables varies greatly between versions earlier and later than CentOS 7.
In versions earlier than CentOS 7, the iptables service is used as the firewall by default. After running the service
iptables stop command, the iptables service will first clear rules and then unload the iptables module. When theiptables service restarts, it will load rules from the configuration file. You can stop the iptables service to test whether
the firewall restrictions were applied.
In versions later than CentOS 7, the firewall service is used as the firewall by default, and the iptables_filter module isloaded to ensure compatibility. You can use the iptables command to add rules. However, the iptables service isdisabled by default. After you confirm that the iptable_filter module is loaded, the rules will take effect.
To determine the firewall, run iptables -nvL to view the rules.
The following two scenarios describe how to configure the iptables firewall software program.
Scenario 1
In an Ubuntu 14 OS, the security group and listening port are enabled, but the Telnet connection fails.
Security group inbound rules:

Security group outbound rules:©2013-2022 Tencent Cloud. All rights reserved.

Page 97 of 131

Cloud Virtual Machine

Telnet connection failure:

Solution
1. Capture the packets on the CVM to check whether the packets were sent to the CVM.
If no, the packets may be blocked by the security group, the upper TGW, or the ISP.
If yes but the CVM does not respond, this issue may be caused by the iptables policy of the CVM. As shown in thefollowing figure, the CVM does not return TCP packets to 64.11 after the Telnet connection is established.

2. After confirming that the issue is caused by the iptables policy, run iptables –nvL to check whether the policy
opened port 8081. In this example, port 8081 is closed.

©2013-2022 Tencent Cloud. All rights reserved.

Page 98 of 131

Cloud Virtual Machine

3. Run the following command to open port 8081:©2013-2022 Tencent Cloud. All rights reserved.

Page 99 of 131

Cloud Virtual Machine

iptables -I INPUT 5 -p tcp--dport 8081 -j ACCEPT

4. Check whether port 8081 is open. If yes, the issue has been solved.
Scenario 2
Based on the iptables configuration, the policy has been enabled, but the destination server still cannot be pinged
through.

©2013-2022 Tencent Cloud. All rights reserved.

Page 100 of 131

Cloud Virtual Machine

SolutionIf the information shown below appears,

run the following command to delete the first output rule:©2013-2022 Tencent Cloud. All rights reserved.

Page 101 of 131

Cloud Virtual Machine

iptables –D OUTPUT 1
Test to verify that the issue has been solved.

How can I remove a firewall?
Windows instances:
1. After logging in to the instance, choose Start > Control Panel > Firewall Settings to access the "Firewall
Settings" page.
2. Check whether the firewall and other security software, such as safedog, have been enabled. If yes, disable them.

©2013-2022 Tencent Cloud. All rights reserved.

Page 102 of 131

Cloud Virtual Machine

Linux instances:
1. Run the following command to check whether the firewall policy has been enabled. If no, skip step 2 and go to step3.

iptables -vnL
2. If the firewall policy has been enabled, run the following command to back up the firewall policy:©2013-2022 Tencent Cloud. All rights reserved.

Page 103 of 131

Cloud Virtual Machine

iptables-save
3. Run the following command to clear the firewall policy:©2013-2022 Tencent Cloud. All rights reserved.

Page 104 of 131

Cloud Virtual Machine

iptables -F

Will the firewall intercept a non-Tencent Cloud CDN CVM?
No. If you are worried that the firewall may disrupt your business, you can disable the firewall.

©2013-2022 Tencent Cloud. All rights reserved.

Page 105 of 131

Cloud Virtual Machine

Operating Systems：

Last updated 2024-01-06 17:26:45

Why an error occurs when I execute an update on Ubuntu OS?
Possible reasons:Tencent Cloud Ubuntu system source is synced with the official source at 00:00, 08:00 and 16:00 every day (UTC+8).
If you run the apt-get update and apt-get install commands just before and after the time points, theapt verification will be failed and an error will occur.
Solution:
Run the apt-get clean all command to purge cache before you run the apt-get update command.

How do I change the owners and owner groups of directories and files on a Linux instance?
If the file or directory permissions are incorrectly configured on the Web server, a 403 error will occur when you accessa website hosted on the instance. Therefore, before you adjust a file or directory, you must confirm the identity underwhich the file or directory process is running.
You can run the ps and grep commands to query the identities under which the file or directory process isrunning.
You can run the ls –l command to query the owners and owner groups of files and directories.
You can run the chown command to modify the permissions. For example, you can run the chown -R www.www/tencentcloud/www/user/ command to change the owners and owner groups of all files and directories under
the /tencentcloud/www/user directory to account “www”.

Do Linux instances support GUI?
Yes. For directions on building GUI on a Linux instance, see Building a Visual Ubuntu Desktop.

How can I activate the operating system of a Windows CVM instance?
You can refer to Activating Windows with slmgr Command or Windows Server System Activation for directions.

Why do I need to boot into the single-user mode on a Linux instance, and how to do this?
Linux's users sometimes need to boot into the single-user mode to perform special operations, such as password
management, sshd repair, or maintenance before disk attaching. For directions, see Booting into Linux Single User
Mode.

How can I check the login logs of a CVM instance?
For more information, see Getting Instance Login Logs.

©2013-2022 Tencent Cloud. All rights reserved.

Page 106 of 131

Cloud Virtual Machine

OPS & Monitoring
Uploading Files：

Last updated 2024-03-26 10:31:21

Does CVM come with FTP?
Yes. You can install and configure FTP as needed.
To build FTP sites using Windows’ built-in FTP service, see Building the FTP Service (Windows).
To build FTP sites using vsftpd software, see Building the FTP Service (Linux).

How do I upload files to a Windows CVM?
For a local Windows, see Uploading Files from Windows to a Windows CVM using MSTSC.
For a local Linux, see Uploading Files from Linux to Windows CVM using RDP.
For a local MacOS, see Uploading Files from MacOS to Windows CVM using MRD.

How does a local host transfer data to and from a Windows CVM?
To transfer data:
If you use the RDP file to log in to a Windows CVM from a local Windows computer, you can directly drag and upload
local files to the CVM.
Upload Files from Windows to a Windows CVM using MSTSC
Build the FTP Service (Linux) on the local host.

How do I upload files to a Linux CVM using WinSCP?
For more information, see Uploading Files via WinSCP to a Linux CVM from Windows.

How do I upload files to or download files from a Linux CVM?
For more information, see Uploading Files via SCP to a Linux CVM from Linux.

What should I do if the client-server connection times out during FTP file upload?
The server firewall or security group may have blocked the connection. Follow the steps below to troubleshoot thisissue:
1. Check the server’s firewall settings.
2. Disable the firewall or add rules.

©2013-2022 Tencent Cloud. All rights reserved.

Page 107 of 131

Cloud Virtual MachineOPS：

Last updated 2024-01-06 17:26:45

Do you have any advice regarding OPS for small websites hosted on CVM?
To maintain the website applications, you can:Back up data to the cloud disk daily. For more information, see Creating Snapshots.
Use SSL Certificates Service for identity verification and encrypted connections.
Install anti-virus plugins or anti-DDoS services or purchase Cloud Workload Protection.
Monitor the traffic to and from the website and identify exceptions in the traffic range. Add the security group rules ofdenied access to temporarily control the exception request of a single point. For more information, see Getting
Monitoring Statistics and Adding Security Group Rules.
Monitor the performance of CVM instances and the cloud disk, and mark the traffic/access peak period. Familiarize
yourself in advance with upgrade/degrade, auto scaling, or cloud disk expansion to respond to request surges. For
more information, see Change Instance Configuration, What is Auto Scaling (AS)?, or Cloud Disk Expansion
Scenarios.
Update the admin password regularly for scenarios where you log in to CVM instances with the root/Administrator
username and password. For more information, see Reset Instance Password.
Update the software patches regularly.

©2013-2022 Tencent Cloud. All rights reserved.

Page 108 of 131

Cloud Virtual Machine

Common Operations and Commands：

Last updated 2024-01-06 17:26:45

What is the Linux server load average?
Load is used to measure the workload of a server; that is, the length of the queue of tasks to be executed by the CPU.
The greater the value, the more processes that are currently running or waiting to be executed.

How can I check the Linux server load?
You can run the w , top , uptime , and procinfo commands or access the /proc/loadavg file toview the load.
Please refer to "Installing Software in the Linux Environment" for instructions on how to install the procinfo tool.

What should I do when the server load is too high?
The server load/load average is displayed based on the length of the process queue. A high server load (werecommend referencing the 15-minute average) may be caused by insufficient CPU resources, I/O read/write
bottlenecks, insufficient memory resources, or intensive computing tasks. We recommend you run the vmstat ,iostat , and top commands to identify the reason for the high load and optimize the processes.

How do I check the server memory usage?
You can check the server memory usage by running the free , top (after running, you can press shift+m tosort the memory), vmstat , and procinfo commands or by accessing the /proc/meminfo file.

How do I check the memory usage of a single process?
You can check the memory usage of a single process by running the top -p PID , pmap -x PID , and ps
aux|grep PID commands or by accessing the /proc/$process_id (process PID) /status file (forexample, the /proc/7159/status file).

How do I check the services and ports that are currently in use?
You can check the services and ports that are currently in use by running the netstat -tunlp , netstat antup , and lsof -i:PORT commands.

How do I check the server process information?
You can check the server process information by running the ps auxww|grep PID , ps -ef , lsof -p
PID , and top -p PID commands.

How do I stop a process?

©2013-2022 Tencent Cloud. All rights reserved.

Page 109 of 131

Cloud Virtual Machine

You can run kill -9 PID (PID indicates the process ID) and killall program name (for example, killallcron) to stop a process.
To stop a zombie process, you need to kill the parent process by running kill -9 ppid (ppid indicates theparent process ID, which can be queried by running ps -o ppid PID (for example, ps -o ppid 32535)).

How do I locate a zombie process?
You can run top to view the total of zombie processes, and run ps -ef | grep defunct | grep -v
grep to locate a specific zombie process.

Why can't I enable the server port?
You need to check the operating system and the application to ensure a port is enabled.
Only the root user can enable ports below 1024 on the Linux operating system. Run sudo su - to obtain root
permissions before enabling the server port.
For application issues such as port conflicts or configuration problems, use the application startup logs to troubleshootthem. The Tencent server system uses port 36000.

What are the commands commonly used to check the performance of a Linux server?
CommandName

top

Description
top is a task manager program that monitors the overall performance of the system.
This command can be used to display information such as the system load, the process, theCPU, the memory, and paging. Use shift+m and shift+p to sort the processes bymemory usage and CPU usage.

vmstatvmstat is a computer system monitoring tool mainly used for virtual memory that collects anddisplays summary information about CPU, processes, memory paging, and IO.
For example, vmstat 3 10 outputs results every 3 seconds and is executed 10 times.

iostatiostat is a computer system monitoring tool that collects and displays statistics about CPU and
IO.
For example, iostat -dxmt 10 outputs detailed information about IO in MB every 10 seconds.

df

df is a command used to display the amount of available disk space.
For example: df -m displays the disk space usage in MB.
lsof reports a list of all open files, which is very useful for Linux system management.
For example:

lsof

lsof -i: 36000 displays the processes using port 36000.
lsof -u root displays the programs run by root.
lsof -c php-fpm displays the files opened by the php-fpm process.
lsof php.ini displays the processes for which php.ini is opened.

©2013-2022 Tencent Cloud. All rights reserved.

Page 110 of 131

Cloud Virtual Machineps

ps is a process query command that displays information related to the processes.
Commonly used command parameter combinations are `ps -ef` and `ps aux`. Use `ps -A -o` tooutput custom fields.
For example:`ps -A -o pid,stat,uname,%cpu,%mem,rss,args,lstart,etime |sort -k6,6 -rn` outputs results
according to the listed fields and sorts them using the 6th field.
`ps -A -o comm |sort -k1 |uniq -c|sort -k1 -rn|head` lists the process with the largest number ofrunning instances.

Other commonly used commands and files: free -m , du , uptime , w , /proc/stat ,/proc/cpuinfo , and /proc/meminfo .

What do I do when Cron doesn’t work?
Follow the steps below to troubleshoot this problem:
1. Verify whether crontab is running normally.
2. Run crontab -e to add the following test item.

©2013-2022 Tencent Cloud. All rights reserved.

Page 111 of 131

Cloud Virtual Machine\\*/1 \\* \\* \\* \\* /bin/date >> /tmp/crontest 2>&1 &3. Check the /tmp/crontest file.
If there are any problems, run ps aux|grep cron to look for the pid of cron, run kill -9 PID to terminate
the cron process, and then run /etc/init.d/cron start to restart cron.
4. Verify whether the script path in the cron entry is an absolute path.
5. Check whether you used the right account to execute cron. Also, check whether the account is included in/etc/cron.deny .
6. Check the execution permission of the script, the script directory, and the log file permission.

©2013-2022 Tencent Cloud. All rights reserved.

Page 112 of 131

Cloud Virtual Machine

7. We recommend that you run the script in the background by adding an "&" at the end of the script entry. For
example, \\*/1 \\* \\* \\* \\* /bin/date >> /tmp/crontest 2>&1 & .

How do I set up a startup task for my CVM instance?
The Linux kernel startup sequence is as follows:
1. Start the /sbin/init process.
2. Run the init initial scripts in sequence.
3. Run the level script /etc/rc.d/rc\\*.d , where the value of * means the running mode, which can be queriedin /etc/inittab .
4. Run /etc/rc.d/rc.local .
Note:
The startup task can be configured in /etc/rc.d/rc.local or in the S\\*\\*rclocal file in/etc/rc.d/rc\\*.d .

Why is the server disk read-only?
Common reasons for a read-only server disk are as follows:
The disk space is full
You can run df -m to check the disk usage and then delete unnecessary files to free disk space. (We do notrecommend you delete non-third party files. Please check the files before you delete them).
Disk inode resources are all occupied
You can run df -i to view and confirm relevant processes.
There is a hardware failure
If none of the above works, please submit a ticket.

How do I view Linux system logs?
The storage path for system-level log files is /var/log .
The commonly used system log is /var/log/messages .

How do I find large files in the file system?
You can find them by following the steps below:
1. Run df to query the disk partition usage (for example, df -m ).
2. Run du to query the size of a specific folder (for example, du -sh ./\\* , du -h --maxdepth=1|head -10 ).
3. Run ls to list the files and file sizes (for example, ls -lSh ).
You can also directly check the size of files under a specific directory by using the find command (for example,
find / -type f -size +10M -exec ls -lrt {} \\ ).

How do I check the version of a server’s operating system?

©2013-2022 Tencent Cloud. All rights reserved.

Page 113 of 131

Cloud Virtual Machine

You can run the following commands to check the version of a server’s operating system:
uname -acat /proc/version
cat /etc/issue

Why are Chinese characters displayed as unintelligible code in the Linux terminal?
The server itself does not impose restrictions on the display language. Therefore, this is most likely a client problem. If
you are using secureCRT, try to change the settings in Options -> Session Options -> Appearance. If you areusing other terminal software, please search on Google for solutions.
If this problem appears in a pure Linux shell, run export to check the user environment variables such as LANG
and LC_CTYPE.

How do I configure a connection timeout using SecureCRT?
You can configure the following settings so that the connection to your CVM instance remains stable when connecting
to CVM via SecureCRT:
1. Open SecureCRT and select Options.
2. Select Session Options and click Terminal.
3. Select Send protocol NO-OP in the Anti-idle box on the right and set the time to “every 120 seconds”.

Why isn't disk space on a Linux server freed after a file is deleted?
Cause:
After logging in to your Linux CVM instance and deleting a file using rm , you may find that the available disk spacedoes not increase when you use df to check the disk space. This is because when the file is deleted, if anotherprocess happens to be accessing the file, the space occupied by the deleted file will not be immediately freed at thetime you check the disk space.
Solution:
1. Run lsof |grep deleted using the root permission and find the PID of the process that is using the deletedfile.
2. Kill the process using kill -9 PID .

How do I delete files on a Linux server?
You can run rm to delete files. Files deleted with this command cannot be recovered. Therefore, please use thiscommand with caution.
Format of rm : rm (option) (parameter) .
Options:-d: directly deletes all hardwired data contained in the directory to be deleted, and then deletes the directory itself.
-f: forcibly deletes a file or a directory.
-i: asks the user before deleting an existing file or directory.

©2013-2022 Tencent Cloud. All rights reserved.

Page 114 of 131

Cloud Virtual Machine-r or -R: deletes all files and sub-directories under a specific directory together using recursive processing.
--preserve-root: does not implement recursive operations on the root directory.
-v: displays the detailed execution processes of the commands.
Parameter: specifies the file or file list to be deleted. If the parameter contains a directory, add the -r or -R
option.
Example:Run rm test.txt to delete the test.txt file.
Run rm -r test to delete the test directory.
Run rm -r * to delete all files and sub-directories under the current directory.

©2013-2022 Tencent Cloud. All rights reserved.

Page 115 of 131

Cloud Virtual Machine

Access Control：

Last updated 2024-01-06 17:26:45

How can I create a custom policy?
If preset policies do not meet your requirements, you can create a custom policy.
The syntax of a custom policy is as follows:{"version": "2.0",©2013-2022 Tencent Cloud. All rights reserved.

Page 116 of 131

Cloud Virtual Machine"statement": [{"action": ["Action"],"resource": "Resource","effect": "Effect"}]}
Action: replace this with the operation to be allowed or denied.
Resource: replace this with the resources that you want to authorize.
Effect: replace this with "Allow" or "Deny".

How should I configure the read-only policy for a CVM?
To allow a user to query CVM instances but not to create, delete, start, or shut down the instances, enable the
QcloudCVMInnerReadOnlyAccess policy.
To do this, log in to the CAM Console. On the Policies page, search for CVM to find the policy.
The policy syntax is as follows:©2013-2022 Tencent Cloud. All rights reserved.

Page 117 of 131

Cloud Virtual Machine{"version": "2.0","statement": [{"action": ["name/cvm:Describe*","name/cvm:Inquiry*"],"resource": "*",
"effect": "allow"}©2013-2022 Tencent Cloud. All rights reserved.

Page 118 of 131

Cloud Virtual Machine]}
The preceding policy grants users the permissions to perform the following operations:
All operations starting with "Describe" in CVM.
All operations starting with "Inquiry" in CVM.

How can I configure the read-only policy for CVM-related resources?
To allow a user to query CVM instances and relevant resources (VPC and CLB instances) but not to create, delete,start, or shut down the instances and relevant resources, enable the QcloudCVMReadOnlyAccess policy.
To do this, log in to the CAM Console. On the Policies page, search for CVM to find the policy.
The policy syntax is as follows:©2013-2022 Tencent Cloud. All rights reserved.

Page 119 of 131

Cloud Virtual Machine{"version": "2.0","statement": [{"action": ["name/cvm:Describe*","name/cvm:Inquiry*"],"resource": "*",
"effect": "allow"},©2013-2022 Tencent Cloud. All rights reserved.

Page 120 of 131

Cloud Virtual Machine{"action": ["name/vpc:Describe*","name/vpc:Inquiry*","name/vpc:Get*"],"resource": "*",
"effect": "allow"},{"action": ["name/clb:Describe*"],"resource": "*",
"effect": "allow"},{"effect": "allow","action": "name/monitor:*","resource": "*"}]}The preceding policy grants users the permissions to perform the following operations:
All operations starting with "Describe" and "Inquiry" in CVM.
All operations starting with "Describe", "Inquiry", and "Get" in VPC.
All operations starting with "Describe" in CLB.
All operations in the monitor.

©2013-2022 Tencent Cloud. All rights reserved.

Page 121 of 131

Cloud Virtual Machine

NTP Service：

Last updated 2024-01-06 17:26:45

How can I adjust the sync interval of NTP after configuring the NTP service?
After configuring the NTP service as instructed in Setting Up NTP Service (Linux), you can restart ntpd to reset thesync interval. To manually set the ntpd synch interval, perform the following steps:
1. Run the following command to modify the NTP configuration file.

©2013-2022 Tencent Cloud. All rights reserved.

Page 122 of 131

Cloud Virtual Machinevi /etc/ntp.conf
2. Press i to enter the edit mode and configure as follows:
2.1 Add the pound sign ( # ) at the beginning of server time1.tencentyun.com iburst , if any, tocomment it out.
2.2 ii. Add the following configurations. minpoll 4 means the minimum interval is 24, and maxpoll 5 means
the maximum interval is 25.

server time1.tencentyun.com minpoll 4 maxpoll 5©2013-2022 Tencent Cloud. All rights reserved.

Page 123 of 131

Cloud Virtual Machine

The result should be as follows. Enter :wq to save changes and close the file.

3. Restart ntpd and run ntpq -p . The poll value you will see is 16 (namely, 24).

What is the time source of Tencent Cloud's ntpd servers?
NTP servers usually use the BeiDou satellite clock.

What should I do when the NTP configuration reports the localhost.localdomain
timeout error?
The error is shown below.

©2013-2022 Tencent Cloud. All rights reserved.

Page 124 of 131

Cloud Virtual Machine

Check and confirm whether you ran POSTROUTING . If yes, change the source IP in the ntp.conf configuration
file to eth0's IP address.

Can off-cloud servers share a NTP with Tencent Cloud CVMs? What is the NTP
synchronization address?
Tencent Cloud provides private NTP servers for Tencent Cloud resources. For other devices, you can use the public
NTP servers provided by Tencent Cloud for synchronization.
Private NTP Server©2013-2022 Tencent Cloud. All rights reserved.

Page 125 of 131

Cloud Virtual Machine

time1.tencentyun.com
time2.tencentyun.com
time3.tencentyun.com
time4.tencentyun.com
time5.tencentyun.com
Public NTP Server

ntp.tencent.com
ntp1.tencent.com
ntp2.tencent.com
ntp3.tencent.com©2013-2022 Tencent Cloud. All rights reserved.

Page 126 of 131

Cloud Virtual Machine

ntp4.tencent.com
ntp5.tencent.com
The following are old public NTP server addresses. These old addresses can still be used, but you are advised to use
the new ones.

time.cloud.tencent.com
time1.cloud.tencent.com
time2.cloud.tencent.com
time3.cloud.tencent.com
time4.cloud.tencent.com©2013-2022 Tencent Cloud. All rights reserved.

Page 127 of 131

Cloud Virtual Machine

time5.cloud.tencent.com

Why is the time of a CVM instance created from a custom image incorrect?
Please check whether the NTP service is enabled. To use the NTP synchronization feature later, see the following
documents to set NTP. Then re-create the custom image.
Setting Up NTP Service (Linux)
Setting Up NTP Service (Windows)

Why is the ntp.conf content of a CVM created from a custom image restored?
It may be caused by the Cloud-Init initialization. Please delete the NTP-related configurations in/etc/cloud/cloud.cfg before creating a custom image. For more information, see Cloud-Init & Cloudbase-Init.

What impact will a modified private network DNS have?
All services involving Tencent Cloud private domain name resolution will be affected. For example,
The YUM repository uses the Tencent Cloud private domain name. You need to modify the YUM repository after
changing DNS.
The reporting of monitoring data uses the private domain name and will be affected.
The NTP feature depends on the private domain name to sync server time, and will be affected.

Why does the local time of a Windows instance reset from the configured EST to UTC+8
after restart?
Check that the windowstime service is enabled on the instance. You may need to manually enable it to auto sync the
instance's system time. We recommend enabling the service autostart.

Why cannot I use the ntpq -np command to view the synchronization time?
The error is shown below.

Please check whether no IP or incorrect IP is configured for listen in the /etc/ntp.conf configuration file.
Change to the primary private IP of the instance and restart ntpd.

How do I fix the error occurred when using the public NTP servers to sync time?
When using the public NTP servers to sync time, the no server suitable for synchronization founderror occurs.

©2013-2022 Tencent Cloud. All rights reserved.

Page 128 of 131

Cloud Virtual MachineThis may be caused by the NTP protection policy in response to the DDoS attacks to the public IP address of theinstance. This policy blocks all public inbound traffic at the Tencent Cloud's source point 123 and causes
synchronization exception. We recommend trying to use the private NTP servers to sync time.

©2013-2022 Tencent Cloud. All rights reserved.

Page 129 of 131

Cloud Virtual Machine

Use Cases：

Last updated 2024-01-06 17:26:45
About Building a Website
Setting up a Website

OPS
CVM Login Failures
Slow Website Access
Website Access Failure
Instance IP Address Ping Failure
How Do I Choose a Certificate?
Passwords
Use Limits
About Building an Environment

Accelerating Software Package Download and Update with Tencent Cloud Software Source
CVM Login Failures
Passwords
Failed to Reset the CVM Password or the CVM Password Is Invalid
Common Operations and Commands
Introduction to Linux Kernel Parameters
Booting into Linux Single User Mode
System and Data Disks
Changing Images (Reinstalling System)
Changing Instance Configuration
About Data Backup
Formatting and Mounting Data Disks
Initializing Data Disks (Windows CVM)
Expanding Cloud Disks
Copying Local Files to CVMs
Backup and Restore
Creating Snapshots©2013-2022 Tencent Cloud. All rights reserved.

Page 130 of 131

Cloud Virtual Machine

Creating Custom Images
Reinstalling System
Snapshots
About Other Use Cases
Security Group Use Cases
Adjusting Security Group Priority
Modifying VNC Resolution
Modifying the Default Remote Port of CVM
CVM Login Failures
Instance IP Address Ping Failure
Failed to Shut Down or Restart a CVM
Failed to Reset the CVM Password or the CVM Password Is Invalid
System Activation
Setup Windows CVM For Multi-user Remote Login©2013-2022 Tencent Cloud. All rights reserved.

Page 131 of 131