Chapter 8. Configuring an iSCSI target Red Hat Enterprise Linux uses the targetcli shell as a command-line interface to perform the following operations: Add, remove, view, and monitor iSCSI storage interconnects to utilize iSCSI hardware. Export local storage resources that are backed by either files, volumes, local SCSI devices, or by RAM disks to remote systems. The targetcli tool has a tree-based layout including built-in tab completion, auto-complete support, and inline documentation. 8.1. Installing targetcli Install the targetcli tool to add, monitor, and remove iSCSI storage interconnects . Procedure Install the targetcli tool: Start the target service: Configure target to start at boot time: Open port 3260 in the firewall and reload the firewall configuration: Verification View the targetcli layout: Additional resources targetcli(8) man page on your system 8.2. Creating an iSCSI target You can create an iSCSI target to let the iSCSI initiator of the client to access the storage devices on the server. Both targets and initiators have unique identifying names. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . Procedure Navigate to the iSCSI directory. You can also use the cd command to navigate to the iSCSI directory. Use one of the following options to create an iSCSI target: Creating an iSCSI target using a default target name: Creating an iSCSI target using a specific name: Replace iqn.2006-04.com.example:444 with the specific target name. Verify the newly created target: Additional resources targetcli(8) man page on your system 8.3. iSCSI Backstore An iSCSI backstore enables support for different methods of storing an exported LUN's data on the local machine. Creating a storage object defines the resources that the backstore uses. An administrator can choose any of the following backstore devices that Linux-IO (LIO) supports: fileio backstore Create a fileio storage object if you are using regular files on the local file system as disk images. For creating a fileio backstore, see Creating a fileio storage object . block backstore Create a block storage object if you are using any local block device and logical device. For creating a block backstore, see Creating a block storage object . pscsi backstore Create a pscsi storage object if your storage object supports direct pass-through of SCSI commands. For creating a pscsi backstore, see Creating a pscsi storage object . ramdisk backstore Create a ramdisk storage object if you want to create a temporary RAM backed device. For creating a ramdisk backstore, see Creating a Memory Copy RAM disk storage object . Additional resources targetcli(8) man page on your system 8.4. Creating a fileio storage object fileio storage objects can support either the write_back or write_thru operations. The write_back operation enables the local file system cache. This improves performance but increases the risk of data loss. It is recommended to use write_back=false to disable the write_back operation in favor of the write_thru operation. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . Procedure Navigate to the fileio/ from the backstores/ directory: Create a fileio storage object: Verification Verify the created fileio storage object: Additional resources targetcli(8) man page on your system 8.5. Creating a block storage object The block driver allows the use of any block device that appears in the /sys/block/ directory to be used with Linux-IO (LIO). This includes physical devices such as, HDDs, SSDs, CDs, and DVDs, and logical devices such as, software or hardware RAID volumes, or LVM volumes. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . Procedure Navigate to the block/ from the backstores/ directory: Create a block backstore: Verification Verify the created block storage object: Additional resources targetcli(8) man page on your system 8.6. Creating a pscsi storage object You can configure, as a backstore, any storage object that supports direct pass-through of SCSI commands without SCSI emulation, and with an underlying SCSI device that appears with lsscsi in the /proc/scsi/scsi such as, a SAS hard drive . SCSI-3 and higher is supported with this subsystem. Warning pscsi should only be used by advanced users. Advanced SCSI commands such as for Asymmetric Logical Unit Assignment (ALUAs) or Persistent Reservations (for example, those used by VMware ESX, and vSphere) are usually not implemented in the device firmware and can cause malfunctions or crashes. When in doubt, use block backstore for production setups instead. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . Procedure Navigate to the pscsi/ from the backstores/ directory: Create a pscsi backstore for a physical SCSI device, a TYPE_ROM device using /dev/sr0 in this example: Verification Verify the created pscsi storage object: Additional resources targetcli(8) man page on your system 8.7. Creating a Memory Copy RAM disk storage object Memory Copy RAM disks ( ramdisk ) provide RAM disks with full SCSI emulation and separate memory mappings using memory copy for initiators. This provides capability for multi-sessions and is particularly useful for fast and volatile mass storage for production purposes. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . Procedure Navigate to the ramdisk/ from the backstores/ directory: Create a 1GB RAM disk backstore: Verification Verify the created ramdisk storage object: Additional resources targetcli(8) man page on your system 8.8. Creating an iSCSI portal You can create an iSCSI portal. This adds an IP address and a port to the target that keeps the target enabled. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . An iSCSI target associated with a Target Portal Groups (TPG). For more information, see Creating an iSCSI target . Procedure Navigate to the TPG directory: Use one of the following options to create an iSCSI portal: Creating a default portal uses the default iSCSI port 3260 and allows the target to listen to all IP addresses on that port: Creating a portal using a specific IP address: Verification Verify the newly created portal: Additional resources targetcli(8) man page on your system 8.9. Creating an iSCSI LUN Logical unit number (LUN) is a physical device that is backed by the iSCSI backstore. Each LUN has a unique number. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . An iSCSI target associated with a Target Portal Groups (TPG). For more information, see Creating an iSCSI target . Created storage objects. For more information, see iSCSI Backstore . Procedure Create LUNs of already created storage objects: Verify the created LUNs: Default LUN name starts at 0 . Important By default, LUNs are created with read-write permissions. If a new LUN is added after ACLs are created, LUN automatically maps to all available ACLs and can cause a security risk. To create a LUN with read-only permissions, see Creating a read-only iSCSI LUN . Configure ACLs. For more information, see Creating an iSCSI ACL . Additional resources targetcli(8) man page on your system 8.10. Creating a read-only iSCSI LUN By default, LUNs are created with read-write permissions. You can create a read-only LUN. Prerequisites Installed and running targetcli . For more information, see Installing targetcli . An iSCSI target associated with a Target Portal Groups (TPG). For more information, see Creating an iSCSI target . Created storage objects. For more information, see iSCSI Backstore . Procedure Set read-only permissions: This prevents the auto mapping of LUNs to existing ACLs allowing the manual mapping of LUNs. Navigate to the initiator_iqn_name directory: Create the LUN: Example: Verify the created LUN: The mapped_lun1 line now has ( ro ) at the end (unlike mapped_lun0's ( rw )) stating that it is read-only. Configure ACLs. For more information, see Creating an iSCSI ACL . Additional resources targetcli(8) man page on your system 8.11. Creating an iSCSI ACL The targetcli service uses Access Control Lists (ACLs) to define access rules and grant each initiator access to a Logical Unit Number (LUN). Both targets and initiators have unique identifying names. You must know the unique name of the initiator to configure ACLs. The /etc/iscsi/initiatorname.iscsi file, provided by the iscsi-initiator-utils package, contains the iSCSI initiator names. Prerequisites The targetcli service is installed and running. An iSCSI target associated with a Target Portal Groups (TPG). Procedure Optional: To disable auto mapping of LUNs to ACLs see Creating a read-only iSCSI LUN . Navigate to the acls directory: Use one of the following options to create an ACL: Use the initiator_iqn_name from the /etc/iscsi/initiatorname.iscsi file on the initiator: Use a custom_name and update the initiator to match it: For information about updating the initiator name, see Creating an iSCSI intiator . Verification Verify the created ACL: Additional resources targetcli(8) man page on your system 8.12. Setting up the Challenge-Handshake Authentication Protocol for the target By using the Challenge-Handshake Authentication Protocol (CHAP) , users can protect the target with a password. The initiator must be aware of this password to be able to connect to the target. Prerequisites Created iSCSI ACL. For more information, see Creating an iSCSI ACL . Procedure Set attribute authentication: Set userid and password : Additional resources targetcli(8) man page on your system 8.13. Removing an iSCSI object using targetcli tool You can remove the iSCSI objects by using the targetcli tool. Procedure Log off from the target: For more information about how to log in to the target, see Creating an iSCSI initiator . Remove the entire target, including all ACLs, LUNs, and portals: Replace iqn.2006-04.com.example:444 with the target_iqn_name. To remove an iSCSI backstore: Replace backstore-type with either fileio , block , pscsi , or ramdisk . Replace block_backend with the backstore-name you want to delete. To remove parts of an iSCSI target, such as an ACL: Verification View the changes: Additional resources targetcli(8) man page on your system

Commands:
yum install targetcli
systemctl start target
systemctl enable target
firewall-cmd --permanent --add-port=3260/tcp Success
firewall-cmd --reload Success
targetcli /> ls o- /........................................[...] o- backstores.............................[...] | o- block.................[Storage Objects: 0] | o- fileio................[Storage Objects: 0] | o- pscsi.................[Storage Objects: 0] | o- ramdisk...............[Storage Objects: 0] o- iscsi...........................[Targets: 0] o- loopback........................[Targets: 0]
/> iscsi/
/iscsi> create Created target iqn.2003-01.org.linux-iscsi.hostname.x8664:sn.78b473f296ff Created TPG1
/iscsi> create iqn.2006-04.com.example:444 Created target iqn.2006-04.com.example:444 Created TPG1 Here iqn.2006-04.com.example:444 is target_iqn_name
/iscsi> ls o- iscsi.......................................[1 Target] o- iqn.2006-04.com.example:444................[1 TPG] o- tpg1...........................[enabled, auth] o- acls...............................[0 ACL] o- luns...............................[0 LUN] o- portals.........................[0 Portal]
/> backstores/fileio
/backstores/fileio> create file1 /tmp/disk1 .img 200M write_back=false Created fileio file1 with size 209715200
/backstores/fileio> ls
/> backstores/block/
/backstores/block> create name= block_backend dev=/dev/ sdb Generating a wwn serial. Created block storage object block_backend using /dev/vdb.
/backstores/block> ls
/> backstores/pscsi/
/backstores/pscsi> create name= pscsi_backend dev=/dev/sr0 Generating a wwn serial. Created pscsi storage object pscsi_backend using /dev/sr0
/backstores/pscsi> ls
/> backstores/ramdisk/
/backstores/ramdisk> create name= rd_backend size= 1GB Generating a wwn serial. Created rd_mcp ramdisk rd_backend with size 1GB.
/backstores/ramdisk> ls
/iscsi> iqn.2006-04.example:444/tpg1/
/iscsi/iqn.20...mple:444/tpg1> portals/ create Using default IP port 3260 Binding to INADDR_Any (0.0.0.0) Created network portal 0.0.0.0:3260
/iscsi/iqn.20...mple:444/tpg1> portals/ create 192.168.122.137 Using default IP port 3260 Created network portal 192.168.122.137:3260
/iscsi/iqn.20...mple:444/tpg1> ls o- tpg.................................. [enambled, auth] o- acls ......................................[0 ACL] o- luns ......................................[0 LUN] o- portals ................................[1 Portal] o- 192.168.122.137:3260......................[OK]
/iscsi/iqn.20...mple:444/tpg1> luns/ create /backstores/ramdisk/rd_backend Created LUN 0. /iscsi/iqn.20...mple:444/tpg1> luns/ create /backstores/block/block_backend Created LUN 1. /iscsi/iqn.20...mple:444/tpg1> luns/ create /backstores/fileio/file1 Created LUN 2.
/iscsi/iqn.20...mple:444/tpg1> ls o- tpg.................................. [enambled, auth] o- acls ......................................[0 ACL] o- luns .....................................[3 LUNs] | o- lun0.........................[ramdisk/ramdisk1] | o- lun1.................[block/block1 (/dev/vdb1)] | o- lun2...................[fileio/file1 (/foo.img)] o- portals ................................[1 Portal] o- 192.168.122.137:3260......................[OK]
/> set global auto_add_mapped_luns=false Parameter auto_add_mapped_luns is now 'false'.
/> iscsi/target_iqn_name/tpg1/acls/ initiator_iqn_name /
/iscsi/target_iqn_name/tpg1/acls/ initiator_iqn_name > create mapped_lun=next_sequential_LUN_number tpg_lun_or_backstore=backstore write_protect=1
/iscsi/target_iqn_name/tpg1/acls/2006-04.com.example:888> create mapped_lun=1 tpg_lun_or_backstore=/backstores/block/block2 write_protect=1 Created LUN 1. Created Mapped LUN 1.
/iscsi/target_iqn_name/tpg1/acls/2006-04.com.example:888> ls o- 2006-04.com.example:888 .. [Mapped LUNs: 2] | o- mapped_lun0 .............. [lun0 block/disk1 (rw)] | o- mapped_lun1 .............. [lun1 block/disk2 (ro)]
/> iscsi/ target_iqn_name / tpg_name /acls/
iscsi/ target_iqn_name / tpg_name /acls> create initiator_iqn_name Created Node ACL for initiator_iqn_name Created mapped LUN 2. Created mapped LUN 1. Created mapped LUN 0.
iscsi/ target_iqn_name / tpg_name /acls> create custom_name Created Node ACL for custom_name Created mapped LUN 2. Created mapped LUN 1. Created mapped LUN 0.
iscsi/ target_iqn_name / tpg_name /acls> ls o- acls .................................................[1 ACL] o- target_iqn_name ....[3 Mapped LUNs, auth] o- mapped_lun0 .............[lun0 ramdisk/ramdisk1 (rw)] o- mapped_lun1 .................[lun1 block/block1 (rw)] o- mapped_lun2 .................[lun2 fileio/file1 (rw)]
/iscsi/iqn.20...mple:444/tpg1> set attribute authentication=1 Parameter authentication is now '1'.
/tpg1> set auth userid= redhat Parameter userid is now ' redhat '. /iscsi/iqn.20...689dcbb3/tpg1> set auth password= redhat_passwd Parameter password is now ' redhat_passwd '.
iscsiadm -m node -T iqn.2006-04.example:444 -u
/> iscsi/ delete iqn.2006-04.com.example:444
/> backstores/ backstore-type / delete block_backend
/> /iscsi/iqn-name/tpg/acls/ delete iqn.2006-04.com.example:444
/> iscsi/ ls