This guide explains how to connect a Synology iSCSI LUN to a Proxmox host and mount it for use with containers (LXC).

⚠️ Important: If using a standard filesystem such as ext4, only one node should mount the LUN at a time. Mounting the same LUN on multiple nodes without a cluster filesystem can cause data corruption.

1) Discover the iSCSI Target

Run the discovery command from your Proxmox node:

iscsiadm -m discovery -t sendtargets -p NAS_IP

Example:

iscsiadm -m discovery -t sendtargets -p 192.168.x.x

You should see output similar to:

192.168.x.x:3260,1 iqn.YYYY-MM.com.synology:target-name

2) Get the Proxmox Initiator Name

You’ll need to add this to the Allow List in Synology DSM.

cat /etc/iscsi/initiatorname.iscsi

Output will look like:

InitiatorName=iqn.YYYY-MM.org.debian:unique-id

Copy everything from iqn onwards and add it to your Synology iSCSI target permissions.

3) Log In to the iSCSI Target

iscsiadm -m node --login

If successful, the session will establish without errors.

To log out from another node (if required):

iscsiadm -m node --logout

4) Confirm the Disk Appears

Check block devices:

lsblk

Or confirm the by-path entry:

ls -l /dev/disk/by-path | grep iscsi

You should see something similar to:

ip-192.168.x.x:3260-iscsi-iqn...-lun-1 -> ../../sdb

5) Format the LUN (If Required)

If this is a new LUN:

mkfs.ext4 /dev/sdX

Replace sdX with the correct device.

6) Create a Mount Point

mkdir -p /mnt/storage

7) Add to /etc/fstab

Edit:

nano /etc/fstab

Add:

/dev/disk/by-path/ip-NAS_IP:3260-iscsi-iqn.TARGET_NAME-lun-1  /mnt/storage  ext4  _netdev,noatime,discard  0  2

Reload systemd and mount:

systemctl daemon-reload
mount -a

8) Ensure iSCSI Auto-Starts on Boot

iscsiadm -m node --op update -n node.startup -v automatic

Verify:

iscsiadm -m node

9) Add Mount to an LXC Container

Edit the container config file:

nano /etc/pve/lxc/CTID.conf

Add at the bottom:

mp0: /mnt/storage,mp=/mnt/storage,backup=0

Restart the container after saving.

Optional Security Recommendation

Consider enabling CHAP authentication on your Synology iSCSI target to prevent unauthorised access, even on internal networks.