iscsiadm

iscsiadm is a command-line utility used to manage iSCSI connections on a Linux system. It is part of the Open-iSCSI package and is used to discover, log in to, log out of, and manage iSCSI sessions and targets. iSCSI (Internet Small Computer System Interface) is a protocol that allows SCSI commands to be sent over IP networks, enabling network-based storage.

Common Usage Scenarios of iscsiadm:

1. Discover iSCSI Targets: You can discover available iSCSI targets on a remote iSCSI server using the discovery command. There are different types of discovery methods:

   • sendtargets: A discovery method where the initiator requests a list of available targets from the target.

   Example command:

   iscsiadm -m discovery -t sendtargets -p <target_ip>

   • -m discovery: Specifies the mode of the operation (discovery mode).

   • -t sendtargets: Uses the SendTargets method of discovery.

   • -p <target_ip>: Specifies the IP address of the iSCSI target server.

2. Login to an iSCSI Target: After discovering the available targets, you can log in to a specific target using the login command.

   Example command:

   iscsiadm -m node -T <target_iqn> -p <target_ip> --login

   • -m node: Specifies node management mode.

   • -T <target_iqn>: Specifies the target IQN (iSCSI Qualified Name) you want to log in to.

   • -p <target_ip>: The IP address of the iSCSI target.

   • --login: Initiates a session with the iSCSI target.

3. Logout from an iSCSI Target: To log out from a connected iSCSI target, use the logout command.

   Example command:

   iscsiadm -m node -T <target_iqn> --logout

   • --logout: Terminates the session with the specified target.

4. List Active iSCSI Sessions: To check the active iSCSI sessions, use the following command:

   iscsiadm -m session

   This will display information about the current iSCSI sessions, including target IQN, session ID, and the IP address of the target.

5. Display Node Information: To display detailed information about a specific iSCSI target (node):

   iscsiadm -m node -T <target_iqn> -p <target_ip>

6. Remove iSCSI Target: If you want to remove a discovered iSCSI target, use the following command:

   iscsiadm -m node -o delete -T <target_iqn> -p <target_ip>

   • -o delete: Deletes the specified iSCSI target configuration.

7. Configure iSCSI Authentication: You can set CHAP (Challenge-Handshake Authentication Protocol) authentication credentials for logging into a target.

   Example command:

   iscsiadm -m node -T <target_iqn> -p <target_ip> --op update -n node.session.auth.username -v <username>
   iscsiadm -m node -T <target_iqn> -p <target_ip> --op update -n node.session.auth.password -v <password>

   • --op update: Updates the specified authentication settings for the target.

   • -n node.session.auth.username: Specifies the CHAP username to be used during login.

   • -n node.session.auth.password: Specifies the CHAP password to be used during login.

8. Rescan iSCSI Targets: After logging in, you can rescan for new or updated LUNs (Logical Unit Numbers) from the connected iSCSI targets.

   iscsiadm -m node -R

   • -R: Rescans the active iSCSI sessions for new LUNs.

Key iscsiadm Command Options:

• -m: Specifies the mode of operation (discovery, node, session, etc.).

• -T: Specifies the target IQN (iSCSI Qualified Name).

• -p: Specifies the target's IP address.

• --login: Logs in to the specified iSCSI target.

• --logout: Logs out from the specified iSCSI target.

• -R: Rescans the target for new LUNs.

• -o delete: Removes the target from the configuration.

• -n: Specifies the node/session option to configure, such as CHAP username or password.

• -v: Specifies the value for the option being updated (e.g., username or password).

iSCSI Configuration Files:

• /etc/iscsi/initiatorname.iscsi: Contains the initiator name (IQN) for the system.

• /etc/iscsi/iscsid.conf: The configuration file for the iSCSI daemon (iscsid). It includes settings for authentication, timeouts, and logging.

Conclusion:

iscsiadm is a powerful and versatile tool for managing iSCSI targets and sessions on Linux systems. It allows administrators to easily discover, connect to, manage, and disconnect from iSCSI storage targets over a network. The flexibility of iscsiadm to manage authentication, perform rescans for new LUNs, and control iSCSI sessions makes it an essential tool for handling network-attached storage in Linux environments.