Conquered a Major Challenge: A Case Study in Troubleshooting
Tags: linux
Published: 2023-07-15 03:59:59

**Problem**

As a software engineer for a large e-commerce company, I was faced with a challenging issue today. The newly launched order management system of the company was not functioning properly. When users attempted to create or view orders, they received an error message indicating that they did not have sufficient permissions to perform this operation. At the same time, our internal team discovered that the server was unable to connect to the internet properly, which was affecting the normal operation of other systems and services.

**Problem Analysis Steps**

1. **Confirm if the server process is running**: My first step was to use the `ps` command and `systemctl status` command to check if the order system service was running, and the results showed that everything was normal.

2. **Check Network Connection**: Then, I used the `ping 8.8.8.8` command to [test the network connection](https://www.howtouselinux.com/post/linux-command-check-network-status-on-linux) and found that our server could not access the internet properly.

3. **Check Server IP Address**: I [found the IP address of the server after using the `ip addr` command](https://www.howtouselinux.com/post/check-ip-address-in-linux) and confirmed that it was not being used by another device and could be accessed by other devices on the network.

4. **Check File Permissions and Ownership**: Next, I used the `ls -l` command to [check the permissions and ownership](https://www.howtouselinux.com/post/check-file-permissions-in-linux) of the files that the order system was trying to access. I noticed that some critical files were owned by a user that was unrelated to the order system, meaning that the order system could not access these files.

5. **Check Server Firewall and SELinux settings**: Lastly, I [checked the SELinux settings](https://www.howtouselinux.com/post/check-selinux-status-in-linux) and did not find any rules that could potentially block our system from accessing the network.

**Problem Solution**

1. **Change File Ownership**: My first step was to use the `chown` command to [change the ownership of the files](https://www.howtouselinux.com/post/linux-command-change-file-permissions-in-linux) to the order system's running user, for example, `sudo chown order_system:order_system /path/to/the/problematic/file`.

2. **Restart Network Service**: I suspected that the network issue might be due to a faulty configuration or failure of the network service, so I attempted to restart the network service using `systemctl restart networking`.

3. **Verify if the issue was resolved**: After making the changes, I restarted the order system and had the internal team and some selected users test it. Fortunately, they were able to create and view orders normally, and our server could also access the internet properly.

Solving this problem required step-by-step troubleshooting, but in the end, we were successful in resolving the issue and got the company's order management system back up and running. This experience emphasized the importance of detailed problem analysis and step-by-step troubleshooting strategy as an engineer.