CentOS 7.x iSCSI initiator client setup

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To use iSCSI drive from a target on a client machine using initiator use following steps:

  1. Ensure that package iscsi-initiator-utils is present
  2. Ensure that InitiatorName is present in /etc/iscsi/initiatorname.iscsi file
  3. Ensure that iscsid service is enabled and running
  4. Discover the target using below command
    iscsiadm -m discovery -t st -p
    iscsiadm --mode discovery --type sendtargets --portal
  5. Login to the discovered target using values from discovery command:
    iscsiadm -m node -T iqn.2003-01.org.linux-iscsi.iscsi.x8664:sn.4f81e28c9c7d -p -l
    Other option is to run discovery with "-l" so that automatic login to all discovered luns is done.
    iscsiadm --mode discovery --type sendtargets --portal -l
  6. Check status of current iscsi sessions on server using (Only in case of Linux target iscsi server):
    targetcli sessions
  7. On client check sessions using:
    iscsiadm -m session
  8. On client disk should be visible using "fdisk -l". However if you want to distinguish between various disks (Say if you have 3 disks all three of 5 GB) then you can look at "/dev/disk/by-path/" devices. In this folder devices are named based on iqn so it is easy to select a disk/lun based on iqn.
  9. If client was already logged in and a new disk is shared it may not become visible directly. To see new disks either
    • Disconnect session as explained in next step and connect again
    • Or rescan SCSI devices using:
      echo "- - -" > /sys/class/scsi_host/host<n>/scan
      where <n> should vary based on folders visible under /sys/class/scsi_host. We need to scan all hosts once using above command.
  10. On client disconnect session using:
    iscsiadm -m session -r <session_number> -u
    where session number is listed using 'iscsiadm -m session' command
  11. On client delete unwanted or wrong discovered sessions using:
    iscsiadm -m discovery
    iscsiadm -m discovery -p -o delete
    If you do not do this and if iscsi server is not available during reboot then system wont boot properly with following lines in /var/log/messages
    Sep 27 20:08:38 barjatiyarklp iscsid: cannot make a connection to (-1,101)
    To fix such a system you would have to boot in single mode and use iscsiadm command with -o delete as explained above
  12. On client various information about iSCSI target is cached in sub-folders inside /var/lib/iscsi folder.


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