iSCSI on Centos 7 Configuration and Setup Guide for Initiator and Target

initiator = client

target = server

These are the first concepts you should understand which is that in iscsi essentially the "initiator" is the client and the "target" is the server.

iSCSI is derived from the old fashioned SCSI that us oldtimers grew to love. The "i" stands for Internet and the SCSI stands for "Small Computers Systems Interface" (SCSI).

iSCSI Target (Server) Setup

targetcli is the package that creates the iSCSI server and allows you to export your devices.

yum -y install targetcli

Loaded plugins: fastestmirror, langpacks Loading mirror speeds from cached hostfile * base: centos.ca-west.mirror.fullhost.io * epel: mirrors.cat.pdx.edu * extras: centos.ca-west.mirror.fullhost.io * updates: centos.ca-west.mirror.fullhost.io Resolving Dependencies --> Running transaction check ---> Package targetcli.noarch 0:2.1.fb46-6.el7_5 will be updated ---> Package targetcli.noarch 0:2.1.fb46-7.el7 will be an update --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Updating: targetcli noarch 2.1.fb46-7.el7 base 67 k Transaction Summary ================================================================================ Upgrade 1 Package Total download size: 67 k Downloading packages: No Presto metadata available for base targetcli-2.1.fb46-7.el7.noarch.rpm | 67 kB 00:00 Running transaction check Running transaction test Transaction test succeeded Running transaction Updating : targetcli-2.1.fb46-7.el7.noarch 1/2 Cleanup : targetcli-2.1.fb46-6.el7_5.noarch 2/2 Verifying : targetcli-2.1.fb46-7.el7.noarch 1/2 Verifying : targetcli-2.1.fb46-6.el7_5.noarch 2/2 Updated: targetcli.noarch 0:2.1.fb46-7.el7 Complete!

systemctl enable target

systemctl start target

systemctl disable firewalld

systemctl stop firewalld

firewall-cmd --permanent --add-port=3260/tcp firewall-cmd --reload

Launch targetcli to configure our iSCSI target

Let's see what block storage/backing devices we have?

/> cd backstores/block /backstores/block> ls o- block .................................................. [Storage Objects: 0] /backstores/block>

Create our iSCSI disk

/backstores/block> create areebsfault /dev/sdb Created block storage object areebsfault using /dev/sdb.

Create our target

The "iqn" must go first and then year-time and then local and finally the "host name" and after the colon the target name "sdb". IQN= iSCSI Qualified Name

iqn
Date (1982-01)
Reversed domain name of the authority (eg. target.abcrandom.local) becomes local.abcrandom.target
Optional “:” that prefixes a storage target name specified by the naming authority

cd /iscsi

/iscsi> create iqn.2018-12.local.abcrandom.target:sdb Created target iqn.2018-12.local.abcrandom.target:sdb. Created TPG 1. Global pref auto_add_default_portal=true Created default portal listening on all IPs (0.0.0.0), port 3260.

Do we have any LUN?

/iscsi/iqn.20...sdb/tpg1/acls> cd /iscsi/iqn.2018-12.local.abcrandom.target:sdb/ /iscsi/iqn.20...om.target:sdb> ls o- iqn.2018-12.local.abcrandom.target:sdb ............................ [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]

Create our LUN

cd /iscsi/iqn.2018-12.local.abcrandom.target:sdb/tpg1/luns

/iscsi/iqn.20...sdb/tpg1/luns> create /backstores/block/areebsfault lun1 Created LUN 1. /iscsi/iqn.20...sdb/tpg1/luns> ls o- luns .............................................................. [LUNs: 1] o- lun1 .................... [block/areebsfault (/dev/sdb) (default_tg_pt_gp)]Create ACL so our initiator can connect

cd /iscsi/iqn.2018-12.local.abcrandom.target:sdb/tpg1/acls

/iscsi/iqn.20...sdb/tpg1/acls> create iqn.1982-01.ca.bla.tld:abc123 Created Node ACL for iqn.1982-01.ca.bla.tld:abc123 Created mapped LUN 1.

*Note the iqn for this ACL as you will need to use it in the clientside (initiator setup).

Client Side Setup

systemctl disable firewalld

systemctl stop firewalld

firewall-cmd --permanent --add-port=3260/tcp firewall-cmd --reload

yum -y install iscsi-initiator-utils

Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: mirror.its.sfu.ca * extras: mirror.its.sfu.ca * updates: mirror.its.sfu.ca Resolving Dependencies --> Running transaction check ---> Package iscsi-initiator-utils.x86_64 0:6.2.0.874-10.el7 will be installed --> Processing Dependency: iscsi-initiator-utils-iscsiuio >= 6.2.0.874-10.el7 for package: iscsi-initiator-utils-6.2.0.874-10.el7.x86_64 --> Running transaction check ---> Package iscsi-initiator-utils-iscsiuio.x86_64 0:6.2.0.874-10.el7 will be installed --> Finished Dependency Resolution Dependencies Resolved ================================================================================ Package Arch Version Repository Size ================================================================================ Installing: iscsi-initiator-utils x86_64 6.2.0.874-10.el7 base 421 k Installing for dependencies: iscsi-initiator-utils-iscsiuio x86_64 6.2.0.874-10.el7 base 92 k Transaction Summary ================================================================================ Install 1 Package (+1 Dependent package) Total download size: 513 k Installed size: 2.6 M Downloading packages: (1/2): iscsi-initiator-utils-6.2.0.874-10.el7.x86_64.rpm | 421 kB 00:00 (2/2): iscsi-initiator-utils-iscsiuio-6.2.0.874-10.el7.x86 | 92 kB 00:00 -------------------------------------------------------------------------------- Total 977 kB/s | 513 kB 00:00 Running transaction check Running transaction test Transaction test succeeded Running transaction Installing : iscsi-initiator-utils-6.2.0.874-10.el7.x86_64 1/2 Installing : iscsi-initiator-utils-iscsiuio-6.2.0.874-10.el7.x86_64 2/2 Verifying : iscsi-initiator-utils-iscsiuio-6.2.0.874-10.el7.x86_64 1/2 Verifying : iscsi-initiator-utils-6.2.0.874-10.el7.x86_64 2/2 Installed: iscsi-initiator-utils.x86_64 0:6.2.0.874-10.el7 Dependency Installed: iscsi-initiator-utils-iscsiuio.x86_64 0:6.2.0.874-10.el7 Complete!

Edit initiatorname.iscsi

vi /etc/iscsi/initiatorname.iscsi

You can also use the echo command (make sure you use the correct iqn):

echo "InitiatorName=iqn.1982-01.ca.bla.tld:abc123" > /etc/iscsi/initiatorname.iscsi

Start and Enable iscsid

[root@localhost ~]# systemctl start iscsid [root@localhost ~]# systemctl enable iscsid Created symlink from /etc/systemd/system/multi-user.target.wants/iscsid.service to /usr/lib/systemd/system/iscsid.service.

Find Targets!

iscsiadm -m discovery --type sendtargets -p 192.168.1.91 192.168.1.91:3260,1 iqn.2018-12.local.abcrandom.target:sdb

If all is well you should see this with ls

ls /var/lib/iscsi/nodes iqn.2018-12.local.abcrandom.target:sdb [root@localhost ~]# ls /var/lib/iscsi/ ifaces/ nodes/ slp/ isns/ send_targets/ static/ [root@localhost ~]# ls /var/lib/iscsi/send_targets/ 192.168.1.91,3260Mount all iscsi targets

iscsiadm -m node -l Logging in to [iface: default, target: iqn.2018-12.local.abcrandom.target:sdb, portal: 192.168.1.91,3260] (multiple) Login to [iface: default, target: iqn.2018-12.local.abcrandom.target:sdb, portal: 192.168.1.91,3260] successful.

You should now see a /dev/sdb available that you can format like a normal disk.

cat /proc/partitions major minor #blocks name 11 0 1048575 sr0 8 0 15728640 sda 8 1 1048576 sda1 8 2 14679040 sda2 253 0 13103104 dm-0 253 1 1572864 dm-1 8 16 4096 sdb

Set it for onboot loading

mkfs.ext4 /dev/sdb1 mke2fs 1.42.9 (28-Dec-2013) Filesystem label= OS type: Linux Block size=1024 (log=0) Fragment size=1024 (log=0) Stride=0 blocks, Stripe width=32764 blocks 1024 inodes, 4092 blocks 204 blocks (4.99%) reserved for the super user First data block=1 Maximum filesystem blocks=4194304 1 block group 8192 blocks per group, 8192 fragments per group 1024 inodes per group Allocating group tables: done Writing inode tables: done Creating journal (1024 blocks): done Writing superblocks and filesystem accounting information: done [root@localhost ~]# blkid /dev/sdb1 /dev/sdb1: UUID="7c1b6358-24b0-4296-b099-13eb1100f72e" TYPE="ext4"

add something like this to /etcfstab

UUID=7c1b6358-24b0-4296-b099-13eb1100f72e /mnt/iscsi ext4 _netdev 0 0

Troubleshooting Common Issues

Firewall Issues. Make sure firewalls are disabled or port 3260 is enabled.
Listening on the wrong IP or port in your portal.
Specifying the target instead of the initiator name/ACL name.
Not creating an LUN
Mixing up different target names with the wrong initiator name.
The client side is using the wrong initiator name (often a random generated one by the OS).

How To

Login To All Targets

iscsiadm -m node -l

Login To Specific Target

iscsiadm -m node -l -T iqn.target.name:bla

Delete your iscsi target

/iscsi> cd /iscsi/ /iscsi> delete iqn.2016-06.localb.a.bla:123 Deleted Target iqn.2016-06.localb.a.bla:123.

Disconnect your client from a target

iscsiadm -m node --logout -T iqn.2018-12.local.abcrandom.target:sdb Logging out of session [sid: 1, target: iqn.2018-12.local.abcrandom.target:sdb, portal: 192.168.1.91,3260] Logout of [sid: 1, target: iqn.2018-12.local.abcrandom.target:sdb, portal: 192.168.1.91,3260] successful.

Disconnect from ALL targets

iscsiadm -m node --logout all Logging out of session [sid: 2, target: iqn.2018-12.local.abcrandom.target:sdb, portal: 192.168.1.91,3260] Logout of [sid: 2, target: iqn.2018-12.local.abcrandom.target:sdb, portal: 192.168.1.91,3260] successful.

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