Linux CentOS 7 - iSCSI configuration

Linux CentOS 7 - iSCSI configuration

Configure the following target on system1: iqn.2019-06.com.example.system1 with 3 GB partition

Configure on system2 an initiator iqn.2019-06.com.example.system2 and automatically mount the iSCSI partion.

On system1

View the partitions
fdisk -l

If there is no space on the present disk, add a new disk.

Configure the new disk.

# fdisk /dev/sdb
n for new
p for primary
1 as the number
first sector: accept default value;
last sector: +4GB
t for type
code 8e for LVM
p to show the configured partition
w to write the configuration and make it permanent

Tell the kernel about the new parttion
# partprobe /dev/sdb

Create a new physical volume
# pvcreate /dev/sdb1

Create a new volume group
# vgcreate vg1 /dev/sdb1

Create a new logical volume
#lvcreate -n lvm1 -l 100%VG vg1

Install packages for target configuration
# yum install -y targetcli

Enable and strart the target service
# systemctl enable target && systemctl start target

Configure the iSCSI target
# targetcli

Configure the block
cd /backstores/block> create block1 /dev/vg1/lvm1

Configure the iscsi target
cd iscsi> create iqn.2019-06.com.example:system1

Configure the ACL
cd iqn.2019-06.com.example:system1/tpg1/acls> create qn.2019-06.com.example:system2

Configure the LUN
cd luns> create /backstores/block/block1

Configure the portal
cd portals> delete 0.0.0.0 3260
create 192.168.189.140:3260

Go to root directory and see the result:
ls

/> ls
o- / ......................................................................................................................... [...]
  o- backstores ....................................................................................................... [...]
  | o- block .................................................................................... [Storage Objects: 1]
  | | o- block1 .......................................... [/dev/vg1/lv1 (2.8GiB) 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.2019-06.com.example:system1 ......................................................... [TPGs: 1]
  |   o- tpg1 .................................................................................... [no-gen-acls, no-auth]
  |     o- acls ....................................................................................................... [ACLs: 1]
  |     | o- iqn.2019-06.com.example:system2 ...................................... [Mapped LUNs: 1]
  |     |   o- mapped_lun0 .............................................................. [lun0 block/block1 (rw)]
  |     o- luns ........................................................................................................ [LUNs: 1]
  |     | o- lun0 .........................................[block/block1 (/dev/vg1/lv1) (default_tg_pt_gp)]
  |     o- portals .................................................................................................. [Portals: 1]
  |       o- 192.168.189.140:3260 ................................................................................. [OK]
  o- loopback ..................................................................................................... [Targets: 0]
/>


Save the configuration
saveconfig
exit

Adjust the firewall
# firewall-cmd --permanent -add-port=3260/tcp

# firewall-cmd --reload

On system2

Install packages for iSCSI initiator

# yum install -y iscsi-initiator-utils

Configure the initiator name

# vim /etc/iscsi/initiatorname.iscsi

InitiatorName=iqn.2019-06.com.example:system2

See the manual pages to copy and adjust sample commands

# man isciadm

Discover the target on the network

# iscsiadm --mode discoverydb --type sendtargets --portal 192.168.189.140 --discover

Login into the target as user root

# iscsiadm --mode node --targetname iqn.2019-06.com.example:system1 --portal 192.168.189.140:3260 --login root

Enable and start the iscsi daemon

# systemctl enable  iscsid && systemctl start  iscsid

Install utility to check iscsi 

# yum install -y lsscsi

Check iscsi targets

# lsscsi
[0:0:0:0]    disk    VMware,  VMware Virtual S 1.0   /dev/sda
[2:0:0:0]    cd/dvd  NECVMWar VMware IDE CDR10 1.00  /dev/sr0
[4:0:0:0]    disk    LIO-ORG  block1           4.0   /dev/sdb

# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   16G  0 disk
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   15G  0 part
  ├─centos-root 253:0    0 13.4G  0 lvm  /
  └─centos-swap 253:1    0  1.6G  0 lvm  [SWAP]
sdb               8:16   0  2.8G  0 disk

# fdisk -l

Configure the iscsi partition

# fdisk /dev/sdb

n for new
p for primary
1 as the number
first sector: accept default value;
last sector: accept default value;
t for type
code 83 for Linux
p to show configured partition
w to save the partion

Format the new partition
# mkfs -t ext4 /dev/sdb1
or shorter
# mkfs.ext4 /dev/sdb1 

View the memory blocks for mounting the iscsi partition

# lsblk

Get the UUID of the blocks

# blkid /dev/sdb1

Copy the UUID into the fstab file

# blkid /dev/sdb1 >> /etc/fstab

Create the mount point for the iscsi partition

# mkdir /iscsi

Edit the /etc/fstab file

UUID="b6ed8784-5417-457e-afe4-b117be65e71d"      /iscsi     ext4      defaults,_netdev 0 0

Mount the whole fstab 

# mount -a

Check the configuration can withstand a reboot

# reboot

# mount | grep iscsi 

it must show no errors and boot OK.