The iscsiadm command in Linux is a core tool for managing iSCSI connections. As a key component of the iSCSI initiator userspace suite, iscsiadm provides comprehensive control over iSCSI nodes, sessions, connections, and discovery history, helping system administrators build stable and efficient storage area networks.

iSCSI technology transmits SCSI commands over TCP/IP, making it possible to build storage area networks on standard network infrastructure. This technology not only reduces storage network deployment costs but also offers performance and reliability comparable to traditional Fibre Channel. As an iSCSI initiator management tool, iscsiadm allows administrators to fine-tune connections to iSCSI targets, ensuring reliable access to storage resources.

Installation and initial configuration are prerequisites for using the iscsiadm command. In Red Hat Enterprise Linux and its derivatives, the iscsi-initiator-utils package must be installed for full iSCSI support. After installation, the iSCSI service uses lazy startup by default and is only started when the iscsid or iscsi kernel module is required for the actual execution of the iscsiadm command. If you need to start the service immediately, you can force activation using the systemctl start iscsid.service command.

Target discovery is the first step in establishing an iSCSI connection. Administrators use the discovery command to locate available iSCSI targets on the network, which serves as the basis for subsequent connection operations. iscsiadm supports multiple discovery methods, the most commonly used of which is the SendTargets method:

iscsiadm -m discovery -t st -p 192.168.1.1:3260

This command queries for iSCSI targets at the specified IP address and port and returns a list of target names. After a successful discovery, the target information is saved in the /var/lib/iscsi/nodes directory, ready for subsequent connection establishment.

Node management covers logging in, logging out, and configuring parameters for iSCSI targets. Logging in to a discovered target can be accomplished with a simple command:

iscsiadm -m node -T iqn.2015.06.example:target -p 192.168.1.1:3260 -l

This command establishes a connection between the initiator and the specified target, making the remote storage device visible to the local system. For environments requiring automated management, you can configure the node to automatically log in:

iscsiadm -m node -T iqn.2015.06.example:target -p 192.168.1.1:3260 --op update -n node.startup -v automatic

With this configuration, the system automatically establishes a connection to the target at startup.

Session management is crucial in complex network storage environments. Administrators need to monitor the status of iSCSI sessions in real time to ensure connection health and stability. You can view currently active iSCSI sessions using the following command:

iscsiadm -m session -P 3

This command displays detailed session information, including the session state, session ID, and information about the SCSI devices accessed through the session. For more concise output, use the iscsiadm -m session command, which displays a list of active sessions in a compact format. If the network configuration or target changes, you may need to rescan sessions to update connection information:

iscsiadm -m session --rescan

This command rescans existing sessions to discover newly added storage devices or logical units.

Security configuration is crucial for iSCSI management. iSCSI supports CHAP authentication, ensuring that only authorized initiators can connect to targets. Configuring CHAP authentication requires executing a series of commands before logging into the target:

iscsiadm -m node -T iqn.2015.06.example:target -o update --name node.session.auth.authmethod --value=CHAP
iscsiadm -m node -T iqn.2015.06.example:target --op update --name node.session.auth.username --value=myuser
iscsiadm -m node -T iqn.2015.06.example:target --op update --name node.session.auth.password --value=mypassword

These commands set the authentication method, username, and password, respectively, establishing a secure connection between the initiator and the target.

Troubleshooting is another important application of the iscsiadm command. When connection anomalies occur or storage device access becomes inaccessible, administrators can utilize the various diagnostic features provided by iscsiadm. By viewing system logs, checking session status, and verifying network connectivity, the root cause can be quickly identified. For abnormal connections, you can terminate the session using the logout command:

iscsiadm -m node -T iqn.2015.06.example:target -p 192.168.1.1:3260 -u

If the connection is completely lost, you may need to use the delete command to completely remove the node record.

The power of the iscsiadm command lies not only in basic connection management but also in its rich parameter options and flexible configuration. From simple single-target connections to complex multipath I/O configurations, iscsiadm provides solutions. In enterprise-class storage environments, mastering the iscsiadm command is crucial for building a high-performance, highly available storage infrastructure.