Simple ISCSI setup in Linux

simple-iscsi-setup-in-linux.md

Mostly gleaned from the instructions at https://wiki.archlinux.org/index.php/ISCSI_Initiator to setup the initiator.

Overview of the steps:

server1 is serving the targets and has IP 10.1.1.1/24 desktop1 is initiator. Both machines are in the 10.1.1.0/24 subnet.

• installed netbsd-iscsi (yum install netbsd-iscsi in my case for Centos 6.5)

• updated the netmask in /etc/iscsi/targets to be 10.1.1.0/24.

• created the empty file that would be the backing store for the target with dd if=/dev/zero of=/tmp/iscsi-target0 bs=1024 count=100000 (this matches what's in the sample config in /etc/iscsi/targets)

• on server1, service netbsd-iscsi start

• lsof the netbsd-iscsi process to see which port it was listening on.

• opened tcp port 3260 on the machine that's the target (iptables -I INPUT -p tcp -s 10.1.1.0/24 --dport 3260 -j ACCEPT)

• Ran iscsiadm -m discovery -t sendtargets -p 10.1.1.1 on desktop1, and saw that target0 was listed

• Did iscsiadm -m node -L all to login to all the targets (only one, target0, was found, so that's the only one I was logging into)

• Did iscsiadm -m session -P 3 and saw which device it was:

  iscsiadm -m session -P 3

           ************************
           Attached SCSI devices:
           ************************
           Host Number: 12 State: running
           scsi12 Channel 00 Id 0 Lun: 0
                   Attached scsi disk sdi          State: running
  

• on desktop1, mke2fs /dev/sdi (prompted me for whole disk, since I didn't use fdisk to create a partition, hit y)

• on desktop1, mount /dev/sdi /mnt

• cp /etc/group /mnt

• umount /mnt from desktop0

• logout of the target using iscsiadm -m node -U all

• on server1, I verified that things were written to the target's backing store with `losetup /dev/loop0 /tmp/iscsi-target0 ; mount /dev/loop0 /mnt ; ls /mnt and saw the group file I copied to it on desktop1. (this is why I didn't run fdisk on /dev/sdi first, so I could easily mount the image on the server using the loopback filesystem without having to calculate partition offsets).

Note that if you have iscsi-initiator-utils and netbsd-iscsi installed on the same machine, both packages put files in /etc/iscsi.

It's unfortunate that ISCSI uses non-standard names for the client and server portions, I find that really confusing. And the target names are overly complex (iqn.1994-04.org.netbsd.iscsi-target:target0 in this default setup, some portion of that is customizable). Getting the target running was pretty straight forward. I find all the initiator side stuff kind of confusing. Of course, you'll want authentication and some kind ACLs on the exported targets, but that's the next step.