Configure iSCSI Initiator and Mount via fstab

0. Notes

When writing this article, I ran the commands as root on Debian 11.

1. Configure iSCSI initiator

a. Install iSCSI initiator tools

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# apt install -y open-iscsi

b. Discover the target

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# iscsiadm -m discovery -t sendtargets -p 10.10.11.6:3260
10.10.11.6:3260,-1 iqn.iscsi.truenas.r510.vmdata1

This returns the IP and IQN addresses of the target. The useful bit is the IQN address.

c. (OPTIONAL) Discover the target using CHAP

If your target requires CHAP for discovery, then you need to follow this step instead of step b.

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# iscsiadm -m discovery -t sendtargets -p 10.10.11.6:3261

This of course would fail but it generates the corresponding sendtargets configuration file.

Edit /etc/iscsi/send_targets/10.10.11.6,3261/st_config to add/change the lines as follows:

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discovery.sendtargets.auth.authmethod = CHAP
discovery.sendtargets.auth.username = example
discovery.sendtargets.auth.password = example_pwd

Then restart the iscsid.service:

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# systemctl restart iscsid

Now use discoverydb mode with the --discover flag passed in to instruct iscsiadm to discover targets using the existing configurations.

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# iscsiadm -m discoverydb -t sendtargets -p 10.10.11.6:3261 --discover
10.10.11.6:3261,-1 iqn.iscsi.truenas.r510.vmdata2

d. Configure CHAP authentication for the node

After the target is discovered, the configuration file of the corresponding node should have been generated.
Edit /etc/iscsi/nodes/iqn.iscsi.truenas.r510.vmdata1/10.10.11.6,3260 to add/change the lines as follows:

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node.session.auth.authmethod = CHAP
node.session.auth.username = example
node.session.auth.password = example_pwd

Then restart the iscsid.service:

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# systemctl restart iscsid

e. Connect to the target

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# iscsiadm -m node -T iqn.iscsi.example.target1 --login
Logging in to [iface: default, target: iqn.iscsi.truenas.r510.vmdata1, portal: 10.10.11.6,3260]
Login to [iface: default, target: iqn.iscsi.truenas.r510.vmdata1, portal: 10.10.11.6,3260] successful.

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# grep "Attached SCSI" /var/log/messages
Aug  7 09:58:18 owncloud kernel: [100867.993240] sd 3:0:0:0: [sdc] Attached SCSI disk

You should be able to also see it using lsblk:

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NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda       8:0    0    1T  0 disk /mnt/owncloud_data_backup
sdb       8:16   0   40G  0 disk 
├─sdb1    8:17   0 39.9G  0 part /
├─sdb14   8:30   0    3M  0 part 
└─sdb15   8:31   0  124M  0 part /boot/efi
sdc       8:32   0    2T  0 disk 
sr0      11:0    1    4M  0 rom

2. Make a file system and mount it in `/etc/fstab`

a. Configure the iSCSI target to connect at system boot

Edit /etc/iscsi/nodes/iqn.iscsi.truenas.r510.vmdata1/10.10.11.6,3260 to change the corresponding line as follows:

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node.startup = automatic

b. Create a file system on the iSCSI disk

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# mkfs.ext4 /dev/sdc

c. Edit `/etc/fstab` to mount the file system automatically at system boot

Get the UUID of the file system:

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# blkid /dev/sdc
/dev/sdc: UUID="e7779e54-9242-4509-a7d6-c01746fc6161" BLOCK_SIZE="4096" TYPE="ext4"

Then add the following line to /etc/fstab:

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UUID=e7779e54-9242-4509-a7d6-c01746fc6161 /mnt/owncloud_data ext4 rw,suid,_netdev,exec,auto,nouser,async 0 2

The fourth field here is based on what the defaults parameter uses as specified in the manual page of fstab, with dev changed to _netdev to ensure the system won’t try mounting the iSCSI disk until network is properly started. To mount the file system immediately instead of waiting until next reboot:

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# mount -a

It should be all good now:

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# lsblk -f
NAME    FSTYPE  FSVER LABEL  UUID                                 FSAVAIL FSUSE% MOUNTPOINT
sda                                                                              
├─sda1  ext4    1.0          a2a6f036-bdc2-4175-828e-722caae22b10   33.9G     9% /
├─sda14                                                                          
└─sda15 vfat    FAT16        D9CD-8857                             113.1M     9% /boot/efi
sdb     ext4    1.0          94c1979f-4214-4f15-9305-af4a0d175e39  221.1G    73% /mnt/owncloud_data_backup
sdc     ext4    1.0          e7779e54-9242-4509-a7d6-c01746fc6161    1.9T     0% /mnt/owncloud_data
sr0     iso9660       cidata 2023-08-06-13-56-57-00

3. References:

Red Hat documentation on iSCSI initiator

Red Hat documentation on setting up CHAP for iSCSI connection

Franciscon Santos' answer in Unix & Linux StackExchange regarding the _netdev mounting parameter