iSCSI, standing for Internet Small Computer System Interface, is a Storage Area Network (SAN) protocol utilized for online storage management. It is an IP-based storage networking standard that provides block-level access to storage devices by carrying SCSI commands over a TCP/IP network.
iSCSI comprises two main components: the iSCSI target and iSCSI initiator. The iSCSI target is a service on the iSCSI server offering access to shared storage, whereas the iSCSI initiator is a client connecting to the target to access the shared storage.
In this guide, we will demonstrate how to set up an iSCSI target and initiator on an Ubuntu 18.04 server.
Requirements
- A fresh Ubuntu 18.04 server for iSCSI target with a 2GB external HDD.
- A fresh Ubuntu 18.04 server for iSCSI initiator.
- A static IP address 192.168.0.103 configured on the iSCSI target and 192.168.0.102 on the iSCSI initiator.
- Root passwords configured on both servers.
Getting Started
Begin by updating both servers to the latest version. Execute the following commands on both servers:
apt-get update -y
apt-get upgrade -y
Reboot both servers to apply changes.
Install iSCSI Target
First, install the Target Framework (TGT) package on the iSCSI target server using the command:
apt-get install tgt -y
After installation, check the TGT status by running:
systemctl status tgt
Expected output:
? tgt.service - (i)SCSI target daemon
Loaded: loaded (/lib/systemd/system/tgt.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2019-11-08 07:40:28 UTC; 27s ago
Docs: man:tgtd(8)
Main PID: 2343 (tgtd)
Status: "Starting event loop..."
Tasks: 1
CGroup: /system.slice/tgt.service
??2343 /usr/sbin/tgtd -f
Nov 08 07:40:28 ubuntu systemd[1]: Starting (i)SCSI target daemon...
Nov 08 07:40:28 ubuntu tgtd[2343]: tgtd: iser_ib_init(3431) Failed to initialize RDMA; load kernel modules?
Nov 08 07:40:28 ubuntu tgtd[2343]: tgtd: work_timer_start(146) use timer_fd based scheduler
Nov 08 07:40:28 ubuntu tgtd[2343]: tgtd: bs_init(387) use signalfd notification
Nov 08 07:40:28 ubuntu systemd[1]: Started (i)SCSI target daemon.
Configure iSCSI Target
Next, create a Logical Unit Number (LUN) device on your iSCSI server. The LUN is a backend storage device that the initiator will later use. Create the configuration file in the /etc/tgt/conf.d directory:
nano /etc/tgt/conf.d/iscsi.conf
Add the following configuration:
<target iqn.2019-11.example.com:lun1>
# Provided device as an iSCSI target
backing-store /dev/sdb1
initiator-address 192.168.0.102
incominguser iscsi-user password
outgoinguser iscsi-target secretpass
</target>
Save the changes and restart the TGT service:
systemctl restart tgt
Configuration explanations:
- target: Name of the specific target.
- backing-store: Specifies the storage disk for the initiator.
- initiator-address: IP address of the initiator.
- incominguser: Provides security credentials for LUN access.
- outgoinguser: Used for mutual CHAP authentication.
Verify the iSCSI target server:
tgtadm --mode target --op show
Expected output confirming the target availability:
Target 1: iqn.2019-11.example.com:lun1
System information:
Driver: iscsi
State: ready
I_T nexus information:
LUN information:
LUN: 0
Type: controller
SCSI ID: IET 00010000
SCSI SN: beaf10
Size: 0 MB, Block size: 1
Online: Yes
Removable media: No
Prevent removal: No
Readonly: No
SWP: No
Thin-provisioning: No
Backing store type: null
Backing store path: None
Backing store flags:
LUN: 1
Type: disk
SCSI ID: IET 00010001
SCSI SN: beaf11
Size: 2146 MB, Block size: 512
Online: Yes
Removable media: No
Prevent removal: No
Readonly: No
SWP: No
Thin-provisioning: No
Backing store type: rdwr
Backing store path: /dev/sdb1
Backing store flags:
Account information:
iscsi-user
iscsi-target (outgoing)
ACL information:
192.168.0.102
Install and Configure iSCSI Initiator
On the iSCSI initiator server, install the iSCSI Initiator package:
apt-get install open-iscsi -y
Then, discover the target on the iSCSI target server:
iscsiadm -m discovery -t st -p 192.168.0.103
Expected discovery output:
192.168.0.103:3260,1 iqn.2019-11.example.com:lun1
This command generates files with LUN information. List them with:
ls -l /etc/iscsi/nodes/iqn.2019-11.example.com\:lun1/192.168.0.103\,3260\,1/ /etc/iscsi/send_targets/192.168.0.103,3260/
Expected files:
/etc/iscsi/nodes/iqn.2019-11.example.com:lun1/192.168.0.103,3260,1/: total 4 -rw------- 1 root root 1840 Nov 8 13:17 default /etc/iscsi/send_targets/192.168.0.103,3260/: total 8 lrwxrwxrwx 1 root root 66 Nov 8 13:17 iqn.2019-11.example.com:lun1,192.168.0.103,3260,1,default -> /etc/iscsi/nodes/iqn.2019-11.example.com:lun1/192.168.0.103,3260,1 -rw------- 1 root root 547 Nov 8 13:17 st_config
Edit the default file to define the CHAP credentials for accessing the iSCSI target:
nano /etc/iscsi/nodes/iqn.2019-11.example.com\:lun1/192.168.0.103\,3260\,1/default
Update the following lines:
node.session.auth.authmethod = CHAP node.session.auth.username = iscsi-user node.session.auth.password = password node.session.auth.username_in = iscsi-target node.session.auth.password_in = secretpass node.startup = automatic
Save and restart the iSCSI initiator service:
systemctl restart open-iscsi
Expected service restart output:
* Unmounting iscsi-backed filesystems [ OK ]
* Disconnecting iSCSI targets iscsiadm: No matching sessions found
[ OK ]
* Stopping iSCSI initiator service [ OK ]
* Starting iSCSI initiator service iscsid [ OK ]
* Setting up iSCSI targets
Logging in to [iface: default, target: iqn.2019-11.example.com:lun1, portal: 192.168.0.103,3260] (multiple)
Login to [iface: default, target: iqn.2019-11.example.com:lun1, portal: 192.168.0.103,3260] successful.
[ OK ]
* Mounting network filesystems [ OK ]
Verify the storage disk is shared from the iSCSI target with:
lsblk
Expected disk availability:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 465.8G 0 disk ??sda1 8:1 0 93.1G 0 part / ??sda2 8:2 0 1K 0 part ??sda5 8:5 0 186.3G 0 part /home ??sda6 8:6 0 181.6G 0 part /Data ??sda7 8:7 0 4.8G 0 part [SWAP] sdb 8:16 0 2G 0 disk
Verify iSCSI connections:
tgtadm --mode conn --op show --tid 1
Expected output:
Session: 1
Connection: 0
Initiator: iqn.1993-08.org.debian:01:2e1e2383de41
IP Address: 192.168.0.102
Create Filesystem and Mount the Shared Device
Create a filesystem on the shared device (sdb) to make it usable:
fdisk /dev/sdb
Expected output walkthrough for partition creation:
Welcome to fdisk (util-linux 2.31.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0x06091fe8.
Command (m for help): n
Partition type
p primary (0 primary, 0 extended, 4 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (1-4, default 1):
First sector (2048-4194303, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-4194303, default 4194303):
Created a new partition 1 of type 'Linux' and of size 2 GiB.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
Format the partition:
mkfs.ext4 /dev/sdb1
Mount the partition to the /mnt directory:
mount /dev/sdb1 /mnt
Verify the mounted device:
df -h
Expected output showing the mounted device:
Filesystem Size Used Avail Use% Mounted on udev 1.9G 4.0K 1.9G 1% /dev tmpfs 384M 1.2M 383M 1% /run /dev/sda1 92G 36G 51G 42% / none 4.0K 0 4.0K 0% /sys/fs/cgroup none 5.0M 0 5.0M 0% /run/lock none 1.9G 54M 1.9G 3% /run/shm none 100M 48K 100M 1% /run/user /dev/sda5 184G 96G 79G 55% /home /dev/sda6 179G 32G 138G 19% /Data /dev/sdb1 2.0G 3.0M 1.9G 1% /mnt
Congratulations! You have successfully installed and configured an iSCSI target server and connected to it from an iSCSI initiator. You can now use this shared iSCSI device like a normal attached disk.
FAQ
- What is iSCSI?
iSCSI, or Internet Small Computer System Interface, is a storage networking standard for accessing storage devices over an IP network. - What are the primary components of iSCSI?
iSCSI consists of an iSCSI target, which provides access to shared storage, and an iSCSI initiator, which acts as a client to access the target. - Which Ubuntu version is this guide for?
This guide is tailored for Ubuntu 18.04 servers. - How much external storage is required for the iSCSI target?
A 2GB external HDD is required for the iSCSI target in this setup. - How do I verify if the iSCSI target is available?
Use the command `tgtadm –mode target –op show` on the target server to verify availability. - What authentication method is used with iSCSI?
CHAP (Challenge-Handshake Authentication Protocol) is used for authentication in this setup.