Network Attached Storage – iSCSI

iSCSI is typically used when you need fast, block‑level storage for workloads such as databases. It isn’t usually something you’d attach to a consumer desktop.

Starting with iSCSI

I prefer to run on Ubuntu, so I’m using the current LTS (24.04.3) for this guide. The server is named vault.

First, update the system:

sudo apt update && sudo apt -y full-upgrade

Next, create the parent directories:

sudo mkdir -p /srv/iscsi

Install the iSCSI target

sudo apt install -y targetcli-fb

Create shared image files

Create some backing files that can be used as targets. Optionally, you can use disk partitions or LVM volumes.

sudo dd if=/dev/zero of=/srv/iscsi/disk00.img bs=1 count=0 seek=50G # Creates a 10GB image file
sudo dd if=/dev/zero of=/srv/iscsi/disk01.img bs=1 count=0 seek=50G # Creates a 50GB image file
sudo dd if=/dev/zero of=/srv/iscsi/disk02.img bs=1 count=0 seek=50G # Creates a 50GB image file
sudo dd if=/dev/zero of=/srv/iscsi/disk03.img bs=1 count=0 seek=50G # Creates a 50GB image file
sudo dd if=/dev/zero of=/srv/iscsi/disk04.img bs=1 count=0 seek=50G # Creates a 50GB image file
sudo dd if=/dev/zero of=/srv/iscsi/disk05.img bs=1 count=0 seek=50G # Creates a 50GB image file

The image files start out small and grow as data is written to them. Be careful not to over‑provision the system, as it becomes a single point of failure for anything that uses iSCSI.

Mount on loopback and format new drives (optional)

sudo losetup -f /srv/iscsi/disk00.img
sudo losetup -a
sudo mkfs.ext4 /dev/loopX   # replace X with the loop device returned by losetup -a
sudo losetup -d /dev/loopX

Or format all of them in one shot:

for image in /srv/iscsi/*.img; do
  sudo losetup -f "$image"
  sudo mkfs.ext4 /dev/loop0
  sudo losetup -d /dev/loop0
done

Configure the iSCSI target using TargetCLI

sudo targetcli

Inside the shell, follow the steps below to create a backstore from the disk images you created.

cd /backstores/fileio
create disk00 /srv/iscsi/disk00.img
create disk01 /srv/iscsi/disk01.img
create disk02 /srv/iscsi/disk02.img
create disk03 /srv/iscsi/disk03.img
create disk04 /srv/iscsi/disk04.img
create disk05 /srv/iscsi/disk05.img

Create the actual LUNs:

cd /iscsi
create iqn.2025-11.com.example:storage
cd iqn.2025-11.com.example:storage/tpg1/luns
create /backstores/fileio/disk00
create /backstores/fileio/disk01
create /backstores/fileio/disk02
create /backstores/fileio/disk03
create /backstores/fileio/disk04
create /backstores/fileio/disk05

To enable authentication:

cd ../
set attribute generate_node_acls=1
set attribute demo_mode_write_protect=0
set attribute authentication=1
set auth userid=your_username
set auth password=your_secret_password

To restrict iSCSI to specific addresses:

cd iqn.2025-11.com.example:storage/tpg1/portals
delete 0.0.0.0:3260
create 10.0.0.5:3260

To save the configuration:

cd /
saveconfig
exit

Verification / validation

sudo targetcli ls

Setup firewall

sudo ufw allow 3260/tcp

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