iSCSI or Internet Small Computer System is a block-level storage solution shares the disks over the network. It depends on the network and strictly recommend to use high throughput interfaces. In iSCSI, we can create various types of iSCSI devices as a fileio or using block devices and logical volumes then present them as targets.

In a small production environment, we are good to use with software iSCSI. However, in critical environment with high load required physical HBA card which will provide high performance. In this guide, we are about to perform installing and configuring software iSCSI server and client on top of Red Hat Enterprise Linux 8.

  • IQN is a unique name to identify the SCSI targets.
  • Target is the server side setup available for Initiator.
  • LUN – Logical unit number

Let start to configure the iSCSI server and client setup in a test environment for demonstration purpose.

iSCSI Target Server Setup

Server IP       : 192.168.107.225
Server Hostname : linuxsysadmins-iSCSI-srv
Server IQN : iqn.2019-04.com.linuxsysadmins.com:tgt0
Port No required: 3260

Installing iSCSI Package

Search for iSCSI server package to start the installation. The targetcli package coming from AppStream repository in Red Hat Enterprise Linux 8 to know how to use and work with AppStream clik here to read.

# dnf search targetcli
# yum search targetcli

Install iSCSI server package “targetcli” using dnf or yum.

# dnf install targetcli -y
# yum install targetcli -y

The output of installation will be similar to below by resolving all required dependencies.

[root@linuxsysadmins-iSCSI-srv ~]# dnf install targetcli -y
Updating Subscription Management repositories.
Last metadata expiration check: 0:10:40 ago on Tue 02 Apr 2019 10:57:50 PM +04.
Dependencies resolved.
Package Arch Version Repository Size
Installing:
targetcli noarch 2.1.fb49-1.el8 AppStream 73 k
Installing dependencies:
cairo x86_64 1.15.12-2.el8 AppStream 721 k
cairo-gobject x86_64 1.15.12-2.el8 AppStream 33 k
libX11 x86_64 1.6.7-1.el8 AppStream 612 k
libX11-common noarch 1.6.7-1.el8 AppStream 157 k
libXau x86_64 1.0.8-13.el8 AppStream 36 k
libXext x86_64 1.3.3-9.el8 AppStream 45 k
libXrender x86_64 0.9.10-7.el8 AppStream 33 k
libxcb x86_64 1.13-5.el8 AppStream 230 k
pixman x86_64 0.34.0-9.el8 AppStream 256 k
python3-cairo x86_64 1.16.3-6.el8 AppStream 90 k
python3-gobject x86_64 3.28.3-1.el8 AppStream 25 k
dejavu-fonts-common noarch 2.35-6.el8 BaseOS 74 k
dejavu-sans-fonts noarch 2.35-6.el8 BaseOS 1.5 M
fontconfig x86_64 2.13.1-2.el8 BaseOS 274 k
fontpackages-filesystem noarch 1.44-22.el8 BaseOS 16 k
python3-configshell noarch 1:1.1.fb25-1.el8 BaseOS 74 k
python3-kmod x86_64 0.9-20.el8 BaseOS 90 k
python3-rtslib noarch 2.1.fb69-2.el8 BaseOS 100 k
python3-urwid x86_64 1.3.1-4.el8 BaseOS 783 k
target-restore noarch 2.1.fb69-2.el8 BaseOS 23 k
Transaction Summary
Install 21 Packages
Total size: 5.1 M
Installed size: 17 M
Running scriptlet: targetcli-2.1.fb49-1.el8.noarch 21/21
Running scriptlet: fontconfig-2.13.1-2.el8.x86_64 21/21
Verifying : cairo-1.15.12-2.el8.x86_64 1/21
Verifying : cairo-gobject-1.15.12-2.el8.x86_64 2/21
Verifying : libX11-1.6.7-1.el8.x86_64 3/21
Verifying : libX11-common-1.6.7-1.el8.noarch 4/21
Verifying : libXau-1.0.8-13.el8.x86_64 5/21
Verifying : libXext-1.3.3-9.el8.x86_64 6/21
Verifying : libXrender-0.9.10-7.el8.x86_64 7/21
Verifying : libxcb-1.13-5.el8.x86_64 8/21
Verifying : pixman-0.34.0-9.el8.x86_64 9/21
Verifying : python3-cairo-1.16.3-6.el8.x86_64 10/21
Verifying : python3-gobject-3.28.3-1.el8.x86_64 11/21
Verifying : targetcli-2.1.fb49-1.el8.noarch 12/21
Verifying : dejavu-fonts-common-2.35-6.el8.noarch 13/21
Verifying : dejavu-sans-fonts-2.35-6.el8.noarch 14/21
Verifying : fontconfig-2.13.1-2.el8.x86_64 15/21
Verifying : fontpackages-filesystem-1.44-22.el8.noarch 16/21
Verifying : python3-configshell-1:1.1.fb25-1.el8.noarch 17/21
Verifying : python3-kmod-0.9-20.el8.x86_64 18/21
Verifying : python3-rtslib-2.1.fb69-2.el8.noarch 19/21
Verifying : python3-urwid-1.3.1-4.el8.x86_64 20/21
Verifying : target-restore-2.1.fb69-2.el8.noarch 21/21
Installed:
targetcli-2.1.fb49-1.el8.noarch cairo-1.15.12-2.el8.x86_64
cairo-gobject-1.15.12-2.el8.x86_64 libX11-1.6.7-1.el8.x86_64
libX11-common-1.6.7-1.el8.noarch libXau-1.0.8-13.el8.x86_64
libXext-1.3.3-9.el8.x86_64 libXrender-0.9.10-7.el8.x86_64
libxcb-1.13-5.el8.x86_64 pixman-0.34.0-9.el8.x86_64
python3-cairo-1.16.3-6.el8.x86_64 python3-gobject-3.28.3-1.el8.x86_64
dejavu-fonts-common-2.35-6.el8.noarch dejavu-sans-fonts-2.35-6.el8.noarch
fontconfig-2.13.1-2.el8.x86_64 fontpackages-filesystem-1.44-22.el8.noarch
python3-configshell-1:1.1.fb25-1.el8.noarch python3-kmod-0.9-20.el8.x86_64
python3-rtslib-2.1.fb69-2.el8.noarch python3-urwid-1.3.1-4.el8.x86_64
target-restore-2.1.fb69-2.el8.noarch
Complete!
[root@linuxsysadmins-iSCSI-srv ~]#

Adding Firewall Rule

From RHEL 7.x all the RHEL based operating systems will come with iSCSI-target firewallD service. Instead of adding a port we required to add the service.

# cat /usr/lib/firewalld/services/iscsi-target.xml

A simple XML format firewall service will make our life more easier.

[root@linuxsysadmins-iSCSI-srv ~]# cat /usr/lib/firewalld/services/iscsi-target.xml 
<?xml version="1.0" encoding="utf-8"?>
<service>
  <short>iSCSI target;/short>>
  <description>Internet SCSI target is a storage resource located on an iSCSI server.</description>
  <port protocol="tcp" port="3260"/>
  <port protocol="udp" port="3260"/>
</service>
[root@linuxsysadmins-iSCSI-srv ~]#

Let’s add the required service, so that we will be good with opening the required ports.

# firewall-cmd --add-service=iscsi-target --permanent
# firewall-cmd --reload
# firewall-cmd --list-all

To make sure the firewall in place verify as shown below. Once the iSCSI service started we need to list the port and check whether it’s listening.

[root@linuxsysadmins-iSCSI-srv ~]# firewall-cmd --add-service=iscsi-target --permanent
success
[root@linuxsysadmins-iSCSI-srv ~]# firewall-cmd --reload
success
[root@linuxsysadmins-iSCSI-srv ~]# firewall-cmd --list-all
public
target: default
icmp-block-inversion: no
interfaces:
sources:
services: cockpit dhcpv6-client iscsi-target ssh
ports:
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:
[root@linuxsysadmins-iSCSI-srv ~]#

Start the “target” service

# systemctl start target
# systemctl enable target
# systemctl status target

Verify target service status by running above command.

[root@linuxsysadmins-iSCSI-srv ~]# systemctl start target
[root@linuxsysadmins-iSCSI-srv ~]#
[root@linuxsysadmins-iSCSI-srv ~]# systemctl enable target
Created symlink /etc/systemd/system/multi-user.target.wants/target.service → /usr/lib/systemd/system/target.service.
[root@linuxsysadmins-iSCSI-srv ~]# systemctl status target
● target.service - Restore LIO kernel target configuration
Loaded: loaded (/usr/lib/systemd/system/target.service; enabled; vendor preset: disabled)
Active: active (exited) since Tue 2019-04-02 23:10:04 +04; 1min 20s ago
Main PID: 9908 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 11368)
Memory: 0B
CGroup: /system.slice/target.service
Apr 02 23:10:04 linuxsysadmins-iSCSI-srv systemd[1]: Starting Restore LIO kernel target configuration…
Apr 02 23:10:04 linuxsysadmins-iSCSI-srv target[9908]: No saved config file at /etc/target/saveconfig.json, ok,>
Apr 02 23:10:04 linuxsysadmins-iSCSI-srv systemd[1]: Started Restore LIO kernel target configuration.
[root@linuxsysadmins-iSCSI-srv ~]#

At last, let us verify the port using “netstat or “ss” command before moving forward.

# netstat -tnlp | grep 3260
# ss -napt | grep 3260

The enabled port for target is Up and we are good to continue with setup.

[root@linuxsysadmins-iSCSI-srv ~]# netstat -tnlp | grep 3260
tcp 0 0 0.0.0.0:3260 0.0.0.0:* LISTEN -
[root@linuxsysadmins-iSCSI-srv ~]#
[root@linuxsysadmins-iSCSI-srv ~]# ss -napt | grep 3260
LISTEN 0 256 0.0.0.0:3260 0.0.0.0:*
[root@linuxsysadmins-iSCSI-srv ~]#

Start Configuring iSCSI Target

To start the iSCSI target configuration we need to run the “targetcli” command from privileged account.

# targetcli

Let’s go through each step, Once we log-in to the target command line press TAB key twice to know all the available commands and options in the targetcli.

Navigate to backstores/block and start to create the backstore using our 2 TB physical disk /dev/sdb.

/backstores/block> create name=LUN0 dev=/dev/sdb

Incase, if we required to create a 1GB of fileio backstore, use below command

cd ../fileio/ create file01 /data/disk1 1G

Then back to / directory of targetcli or navigate to iscsi path using cd ../../iscsi.

cd ../../iscsi

Create an IQN for the target, When we are creating the IQN it will manage to create the TPG under this IQN.

create iqn.2019-04.com.linuxsysadmins.com:tgt0

From created IQN navigate to LUNs and map it.

cd iqn.2019-04.com.linuxsysadmins.com:tgt0/tpg1/luns

Create the LUN

create /backstores/block/LUN0

Navigate to ACL under target and create one for the client nodes.

cd ../acls

Allow the client machine by creating an ACL.

create iqn.2019-04.com.linuxsysadmins:client01

Navigate to created ACL and set and username and password for CHAP authentication

cd iqn.2019-04.com.linuxsysadmins:client01/

Choose any username and password

set auth userid=linuxsysadmins
set auth password=sysadmins@123

Creating portal will be automatically done while we create with IQN.

To make all changes persistent navigate to root directory of targetcli and run the command “saveconfig to save the configuration in json format. And type “exit” to come out of targetcli.

cd ../../../../
saveconfig
exit

The RAW output from command line is below for your reference.

[root@linuxsysadmins-iSCSI-srv ~]# targetcli
targetcli shell version 2.1.fb49
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.
/>
/> ls
o- / …………………………………………………………………………………………………………. […]
o- backstores ……………………………………………………………………………………………….. […]
| o- block …………………………………………………………………………………….. [Storage Objects: 0]
| o- fileio ……………………………………………………………………………………. [Storage Objects: 0]
| o- pscsi …………………………………………………………………………………….. [Storage Objects: 0]
| o- ramdisk …………………………………………………………………………………… [Storage Objects: 0]
o- iscsi ……………………………………………………………………………………………… [Targets: 0]
o- loopback …………………………………………………………………………………………… [Targets: 0]
/>
/> cd backstores/block
/backstores/block>
/backstores/block> create name=LUN0 dev=/dev/sdb
Created block storage object LUN0 using /dev/sdb.
/backstores/block>
/backstores/block> ls
o- block ………………………………………………………………………………………… [Storage Objects: 1]
o- LUN0 ……………………………………………………………………. [/dev/sdb (2.0TiB) write-thru deactivated]
o- alua …………………………………………………………………………………………. [ALUA Groups: 1]
o- default_tg_pt_gp ………………………………………………………………… [ALUA state: Active/optimized]
/backstores/block>
/backstores/block> cd ../..
/>
/> cd iscsi
/iscsi>
/iscsi> create iqn.2019-04.com.linuxsysadmins.com:tgt0
Created target iqn.2019-04.com.linuxsysadmins.com:tgt0.
Created TPG 1.
Global pref auto_add_default_portal=true
Created default portal listening on all IPs (0.0.0.0), port 3260.
/iscsi>
/iscsi> ls
o- iscsi ……………………………………………………………………………………………….. [Targets: 1]
o- iqn.2019-04.com.linuxsysadmins.com:tgt0 ………………………………………………………………….. [TPGs: 1]
o- tpg1 ……………………………………………………………………………………. [no-gen-acls, no-auth]
o- acls ……………………………………………………………………………………………… [ACLs: 0]
o- luns ……………………………………………………………………………………………… [LUNs: 0]
o- portals ………………………………………………………………………………………… [Portals: 1]
o- 0.0.0.0:3260 …………………………………………………………………………………………. [OK]
/iscsi>
/iscsi> cd iqn.2019-04.com.linuxsysadmins.com:tgt0/tpg1/luns
/iscsi/iqn.20…gt0/tpg1/luns> ls
o- luns …………………………………………………………………………………………………… [LUNs: 0]
/iscsi/iqn.20…gt0/tpg1/luns> create /backstores/block/LUN0
Created LUN 0.
/iscsi/iqn.20…gt0/tpg1/luns> ls
o- luns …………………………………………………………………………………………………… [LUNs: 1]
o- lun0 ……………………………………………………………………. [block/LUN0 (/dev/sdb) (default_tg_pt_gp)]
/iscsi/iqn.20…gt0/tpg1/luns> cd ../acls
/iscsi/iqn.20…gt0/tpg1/acls>
/iscsi/iqn.20…gt0/tpg1/acls> create iqn.2019-04.com.linuxsysadmins:client01
Created Node ACL for iqn.2019-04.com.linuxsysadmins:client01
Created mapped LUN 0.
/iscsi/iqn.20…gt0/tpg1/acls> ls
o- acls …………………………………………………………………………………………………… [ACLs: 1]
o- iqn.2019-04.com.linuxsysadmins:client01 ………………………………………………………… [Mapped LUNs: 1]
o- mapped_lun0 ……………………………………………………………………………… [lun0 block/LUN0 (rw)]
/iscsi/iqn.20…gt0/tpg1/acls> cd iqn.2019-04.com.linuxsysadmins:client01/
/iscsi/iqn.20….com:client01>
/iscsi/iqn.20….com:client01> ls
o- iqn.2019-04.com.linuxsysadmins:client01 ………………………………………………………….. [Mapped LUNs: 1]
o- mapped_lun0 ……………………………………………………………………………….. [lun0 block/LUN0 (rw)]
/iscsi/iqn.20….:client01> set auth userid=linuxsysadmins
Parameter userid is now 'linuxsysadmins'.
/iscsi/iqn.20….:client01> set auth password=sysadmins@123
Parameter password is now 'sysadmins@123'.
/iscsi/iqn.20….:client01>
/iscsi/iqn.20….:client01> cd ../../../../
/iscsi> cd ..
/> saveconfig
Configuration saved to /etc/target/saveconfig.json
/>
/>
/> ls
o- / …………………………………………………………………………………………………………. […]
o- backstores ……………………………………………………………………………………………….. […]
| o- block …………………………………………………………………………………….. [Storage Objects: 1]
| | o- LUN0 ………………………………………………………………….. [/dev/sdb (2.0TiB) write-thru activated]
| | o- alua ……………………………………………………………………………………… [ALUA Groups: 1]
| | o- default_tg_pt_gp …………………………………………………………….. [ALUA state: Active/optimized]
| o- fileio ……………………………………………………………………………………. [Storage Objects: 0]
| o- pscsi …………………………………………………………………………………….. [Storage Objects: 0]
| o- ramdisk …………………………………………………………………………………… [Storage Objects: 0]
o- iscsi ……………………………………………………………………………………………… [Targets: 1]
| o- iqn.2019-04.com.linuxsysadmins.com:tgt0 ………………………………………………………………… [TPGs: 1]
| o- tpg1 ………………………………………………………………………………….. [no-gen-acls, no-auth]
| o- acls ……………………………………………………………………………………………. [ACLs: 1]
| | o- iqn.2019-04.com.linuxsysadmins:client01 …………………………………………………. [Mapped LUNs: 1]
| | o- mapped_lun0 ………………………………………………………………………. [lun0 block/LUN0 (rw)]
| o- luns ……………………………………………………………………………………………. [LUNs: 1]
| | o- lun0 …………………………………………………………….. [block/LUN0 (/dev/sdb) (default_tg_pt_gp)]
| o- portals ………………………………………………………………………………………. [Portals: 1]
| o- 0.0.0.0:3260 ……………………………………………………………………………………….. [OK]
o- loopback …………………………………………………………………………………………… [Targets: 0]
/>
/> exit
Global pref auto_save_on_exit=true
Last 10 configs saved in /etc/target/backup/.
Configuration saved to /etc/target/saveconfig.json
iSCSI after creating LUN
Listing a created iSCSI LUN

That’s it we have completed with configuring iSCSI Target in RHEL 8 server. The same steps are applied for RHEL 7.x servers as-well.


Client Side Configurations

Client side configuration is super easy and make sure to use the man page effectively.

Client             : 192.168.107.130
Server Name : linuxsysadmins-client
Initiator IQN : iqn.2019-04.com.linuxsysadmins:client01

Install the iSCSI initiator package using dnf or yum.

# dnf search iscsi-initiator-utils
# dnf install iscsi-initiator-utils -y
# yum search iscsi-initiator-utils
# yum install iscsi-initiator-utils -y

Very less numbers of packages and dependencies are resolved for client setup.

[root@linuxsysadmins-client ~]# dnf install iscsi-initiator-utils -y
Updating Subscription Management repositories.
Last metadata expiration check: 0:01:50 ago on Tue 02 Apr 2019 09:11:25 PM EDT.
Dependencies resolved.
Package Arch Version Repository
Size
Installing:
iscsi-initiator-utils x86_64 6.2.0.876-5.gitf3c8e90.el8 BaseOS 371 k
Installing dependencies:
iscsi-initiator-utils-iscsiuio x86_64 6.2.0.876-5.gitf3c8e90.el8 BaseOS 98 k
isns-utils-libs x86_64 0.97-6.el8 BaseOS 105 k
Transaction Summary
Install 3 Packages
Total size: 574 k
Installed size: 2.5 M
Downloading Packages:
Installed:
iscsi-initiator-utils-6.2.0.876-5.gitf3c8e90.el8.x86_64
iscsi-initiator-utils-iscsiuio-6.2.0.876-5.gitf3c8e90.el8.x86_64
isns-utils-libs-0.97-6.el8.x86_64
Complete!
[root@linuxsysadmins-client ~]#

During the target server setup, we have created ACL for IQN “iqn.2019-04.com.linuxsysadmins:client01” so we need to use the same in client side. Replace the existing initiator name with below one.

# vi /etc/iscsi/initiatorname.iscsi
iqn.2019-04.com.linuxsysadmins:client01

ACL for the target has been defined with user authentication so its time to append them in the conf file. Edit the iscsid.conf and navigate to line number 58, 62, 63 and make sure to change the required parameters as shown below.

# vi +58 /etc/iscsi/iscsid.conf

Un-comment the line number 58 defined for session required “auth.authmethod“. By following un-comment the credentials line and replace “username” and “password” with our credentials.

#node.session.auth.authmethod = CHAP
#node.session.auth.username = username
#node.session.auth.password = password
To
node.session.auth.authmethod = CHAP
node.session.auth.username = linuxsysadmins
node.session.auth.password = sysadmins@123

Once completed with configuring the parameters under iscsid.conf start the iSCSI initiator service.

# systemctl start iscsi
# systemctl status iscsi

Discovering iSCSI storage

Now it’s time to discover the iSCSI target. Using the man page grab the required commands with option and argument. To discover and perform a log-in the “iscsiadmin” command comes with long options and argument. Run the manual and navigate to the end of the man page using “SHIFT+G” you will find the example as shown below, Just we need to replace the server information and start the discovery.

# man iscsiadm
Using man page for iscsiadm
Using man page for iscsiadm

Replace the IP of iSCSI server after “–portal” as shown below.

# iscsiadm --mode discoverydb --type sendtargets --portal 192.168.107.225 --discover

Once discovered we will get the target details as follows.

[root@linuxsysadmins-client ~]# iscsiadm --mode discoverydb --type sendtargets --portal 192.168.107.225 --discover
192.168.107.225:3260,1 iqn.2019-04.com.linuxsysadmins.com:tgt0

Now it’s time to login into the iSCSI storage from our initiator. Replace the default IQN with discovered one and try to log-in.

# iscsiadm --mode node --targetname iqn.2019-04.com.linuxsysadmins.com:tgt0 --portal 192.168.107.225 --login
 [root@linuxsysadmins-client ~]#
[root@linuxsysadmins-client ~]# iscsiadm --mode node --targetname iqn.2019-04.com.linuxsysadmins.com:tgt0 --portal 192.168.107.225 --login
Logging in to iface: default, target: iqn.2019-04.com.linuxsysadmins.com:tgt0, portal: 192.168.107.225,3260
Login to [iface: default, target: iqn.2019-04.com.linuxsysadmins.com:tgt0, portal: 192.168.107.225,3260] successful.
[root@linuxsysadmins-client ~]#

In case if you required to check the session and node information of target we can use below commands.

# iscsiadm --mode session
# iscsiadm --mode node

Session and node information as follows.

[root@linuxsysadmins-client ~]# iscsiadm --mode node
192.168.107.225:3260,1iqn.2019-04.com.linuxsysadmins.com:tgt0
[root@linuxsysadmins-client ~]#
[root@linuxsysadmins-client ~]# iscsiadm --mode session
tcp: [4] 192.168.107.225:3260,1 iqn.2019-04.com.linuxsysadmins.com:tgt0 (non-flash)
[root@linuxsysadmins-client ~]#
[root@linuxsysadmins-client ~]#

Monitoring logs

A successful login will get the output similar to below. To get more information it’s good to do a tail on “/var/log/messages“.

[root@linuxsysadmins-client ~]# tail -f /var/log/messages
Apr 2 22:22:12 linuxsysadmins-client kernel: scsi host32: iSCSI Initiator over TCP/IP
Apr 2 22:22:12 linuxsysadmins-client kernel: scsi 32:0:0:0: Direct-Access LIO-ORG LUN0 4.0 PQ: 0 ANSI: 5
Apr 2 22:22:12 linuxsysadmins-client kernel: scsi 32:0:0:0: alua: supports implicit and explicit TPGS
Apr 2 22:22:12 linuxsysadmins-client kernel: scsi 32:0:0:0: alua: device naa.600140513e6bdd6cefc417388e3c4d34 port group 0 rel port 1
Apr 2 22:22:12 linuxsysadmins-client kernel: scsi 32:0:0:0: Attached scsi generic sg1 type 0
Apr 2 22:22:12 linuxsysadmins-client kernel: sd 32:0:0:0: alua: transition timeout set to 60 seconds
Apr 2 22:22:12 linuxsysadmins-client kernel: sd 32:0:0:0: alua: port group 00 state A non-preferred supports TOlUSNA
Apr 2 22:22:12 linuxsysadmins-client kernel: sd 32:0:0:0: [sda] 4294967296 512-byte logical blocks: (2.20 TB/2.00 TiB)
Apr 2 22:22:12 linuxsysadmins-client kernel: sd 32:0:0:0: [sda] Write Protect is off
Apr 2 22:22:12 linuxsysadmins-client kernel: sd 32:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Apr 2 22:22:12 linuxsysadmins-client kernel: sd 32:0:0:0: [sda] Attached SCSI disk
Apr 2 22:22:13 linuxsysadmins-client iscsid[940]: Could not set session4 priority. READ/WRITE throughout and latency could be affected.
Apr 2 22:22:13 linuxsysadmins-client iscsid[940]: Connection4:0 to [target: iqn.2019-04.com.linuxsysadmins.com:tgt0, portal: 192.168.107.225,3260] through [iface: default] is operational now

Listing the iSCSI disks

Once we login to iSCSI storage we will get a SAN disk in our server. To list the new disk we can use anyone of below commands.

# lsiscsi -d

Output as follows:

[root@linuxsysadmins-client ~]# lsscsi -d
[3:0:0:0] cd/dvd NECVMWar VMware SATA CD01 1.00 /dev/sr0 [11:0]
[32:0:0:0] disk LIO-ORG LUN0 4.0 /dev/sda [8:0]
[N:0:0:1] disk VMware Virtual NVMe Disk__1 /dev/nvme0n1 [259:0]
[root@linuxsysadmins-client ~]#
[root@linuxsysadmins-client ~]# lsblk --scsi
NAME HCTL TYPE VENDOR MODEL REV TRAN
sda 32:0:0:0 disk LIO-ORG LUN0 4.0 iscsi
sr0 3:0:0:0 rom NECVMWar VMware SATA CD01 1.00 sata
[root@linuxsysadmins-client ~]#

Listing all available block devices and it’s UUID using “blkid“.

# lsblk
# lsblk --scsi
# blkid /dev/sda

Listing all available block devices.

[root@linuxsysadmins-client ~]# lsblk 
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 2T 0 disk
sr0 11:0 1 6.5G 0 rom
nvme0n1 259:0 0 20G 0 disk
|-nvme0n1p1 259:1 0 1G 0 part /boot
-nvme0n1p2 259:2 0 19G 0 part |-rhel-root 253:0 0 17G 0 lvm / -rhel-swap 253:1 0 2G 0 lvm [SWAP]
[root@linuxsysadmins-client ~]#

[root@linuxsysadmins-client ~]# blkid /dev/sda
/dev/sda: UUID="19367bf8946c48ac9ac68662ea46b14e" POOL_UUID="9fa5b3250f51484d91faf0bc78138fdb" BLOCKDEV_SECTORS="4294967296" BLOCKDEV_INITTIME="1549484384" TYPE="stratis"
[root@linuxsysadmins-client ~]#

In any case, if we required more verbose information about the session use “-m” or “–mode” and specify the mode (session, node, host iface and discoverydb) print (-P) the session tree format with more verbose.

# iscsiadm -m session -P 3

Output of session information in print level 3.

[root@linuxsysadmins-client ~]# iscsiadm -m session -P 3
iSCSI Transport Class version 2.0-870
version 6.2.0.876-5
Target: iqn.2019-04.com.linuxsysadmins.com:tgt0 (non-flash)
Current Portal: 192.168.107.225:3260,1
Persistent Portal: 192.168.107.225:3260,1
Interface:
Iface Name: default
Iface Transport: tcp
Iface Initiatorname: iqn.2019-04.com.linuxsysadmins.com:client01
Iface IPaddress: 192.168.107.130
Iface HWaddress: default
Iface Netdev: default
SID: 4
iSCSI Connection State: LOGGED IN
iSCSI Session State: LOGGED_IN
Internal iscsid Session State: NO CHANGE
*
Timeouts:
*
Recovery Timeout: 120
Target Reset Timeout: 30
LUN Reset Timeout: 30
Abort Timeout: 15

CHAP:

username: linuxsysadmins
password:
username_in:
password_in:
Negotiated iSCSI params:
HeaderDigest: None
DataDigest: None
MaxRecvDataSegmentLength: 262144
MaxXmitDataSegmentLength: 262144
FirstBurstLength: 65536
MaxBurstLength: 262144
ImmediateData: Yes
InitialR2T: Yes
MaxOutstandingR2T: 1
Attached SCSI devices:
Host Number: 32 State: running
scsi32 Channel 00 Id 0 Lun: 0
Attached scsi disk sda State: running
[root@linuxsysadmins-client ~]#

Logout a iSCSI node

We are covering only for informational how to logout a session. But in a production environment this should not be performed until unless we required for some troubleshooting during an Incident, If do so it will end up in data loss and cause more disaster.

To logout the session we required to replace the “–login” with “–logout“.

# iscsiadm --mode node --targetname iqn.2019-04.com.linuxsysadmins.com:tgt0 --portal 192.168.107.225:3260 --logout

Troubleshooting iSCSI

It’s good to know where iSCSI portals discovery information and node information are stored. This will help during iSCSI troubleshooting.

# cd /var/lib/iscsi

Partitioning and Creating file System

To partition and creating a file system on top of any disks kindly refer below articles.

Are you looking to create a Logical volume or VDO on top of above 2 TB LUN? Have a look at below.

Conclusion

We have seen how to set up an iSCSI Target (Server) and get the disks in an Initiator (Client). iSCSI is a poor man’s SAN which easier to set up in any flavour of Linux servers. Let see you soon in the next guide, Subscribe to our newsletter and receive our updates once we posted. Your comments are most welcome, kindly let us know if any correction needs to be updated.

Babin Lonston
Overall 14+ Years of experience in IT field, 7+ years of experience in Linux administration with Virtualization & Cloud technologies. Love documentation and being Numismatics for a long time.

Using AppStream with yum in Red Hat Enterprise Linux 8

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