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iSCSI devices

(Written by Paul Cobbaut, https://github.com/paulcobbaut/)

This chapter teaches you how to setup an iSCSI target server and an iSCSI initiator client.

iSCSI terminology

iSCSI is a protocol that enables SCSI over IP. This means that you can have local SCSI devices (like /dev/sdb) without having the storage hardware in the local computer.

The computer holding the physical storage hardware is called the iSCSI Target. Each individual addressable iSCSI device on the target server will get a LUN number.

The iSCSI client computer that is connecting to the Target server is called an Initiator. An initiator will send SCSI commands over IP instead of directly to the hardware. The Initiator will connect to the Target.

iSCSI Target in RHEL/CentOS

This section will describe iSCSI Target setup on RHEL6, RHEL7 and CentOS.

Start with installing the iSCSI Target package.

yum install scsi-target-utils

We configure three local disks in /etc/tgt/targets.conf to become three LUN\'s.

<target iqn.2008-09.com.example:server.target2>
    direct-store /dev/sdb
    direct-store /dev/sdc
    direct-store /dev/sdd
    incominguser paul hunter2
</target>

Restart the service.

[root@linux ~]# service tgtd start
Starting SCSI target daemon:                               [  OK  ]

The standard local port for iSCSI Target is 3260, in case of doubt you can verify this with netstat.

[root@server1 tgt]# netstat -ntpl | grep tgt
tcp    0   0 0.0.0.0:3260       0.0.0.0:*          LISTEN      1670/tgtd
tcp    0   0 :::3260            :::*               LISTEN      1670/tgtd

The tgt-admin -s command should now give you a nice overview of the three LUN\'s (and also LUN 0 for the controller).

[root@server1 tgt]# tgt-admin -s
Target 1: iqn.2014-04.be.linux-training:server1.target1
    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
            Backing store type: null
            Backing store path: None
            Backing store flags: 
        LUN: 1
            Type: disk
            SCSI ID: IET     00010001
            SCSI SN: VB9f23197b-af6cfb60 
            Size: 1074 MB, Block size: 512
            Online: Yes
            Removable media: No
            Prevent removal: No
            Readonly: No
            Backing store type: rdwr
            Backing store path: /dev/sdb
            Backing store flags: 
        LUN: 2
            Type: disk
            SCSI ID: IET     00010002
            SCSI SN: VB8f554351-a1410828 
            Size: 1074 MB, Block size: 512
            Online: Yes
            Removable media: No
            Prevent removal: No
            Readonly: No
            Backing store type: rdwr
            Backing store path: /dev/sdc
            Backing store flags: 
        LUN: 3
            Type: disk
            SCSI ID: IET     00010003
            SCSI SN: VB1035d2f0-7ae90b49 
            Size: 1074 MB, Block size: 512
            Online: Yes
            Removable media: No
            Prevent removal: No
            Readonly: No
            Backing store type: rdwr
            Backing store path: /dev/sdd
            Backing store flags: 
    Account information:
    ACL information:
        ALL

iSCSI Initiator in RHEL/CentOS

This section will describe iSCSI Initiator setup on RHEL6, RHEL7 and CentOS.

Start with installing the iSCSI Initiator package.

[root@server2 ~]# yum install iscsi-initiator-utils

Then ask the iSCSI target server to send you the target names.

[root@server2 ~]# iscsiadm -m discovery -t sendtargets -p 192.168.1.95:3260
Starting iscsid:                                           [  OK  ]
192.168.1.95:3260,1 iqn.2014-04.be.linux-training:centos65.target1

We received iqn.2014-04.be.linux-training:centos65.target1.

We use this iqn to configure the username and the password (paul and hunter2) that we set on the target server.

[root@server2 iscsi]# iscsiadm -m node --targetname iqn.2014-04.be.linux-tra\
ining:centos65.target1 --portal "192.168.1.95:3260" --op=update --name node.\
session.auth.username --value=paul
[root@server2 iscsi]# iscsiadm -m node --targetname iqn.2014-04.be.linux-tra\
ining:centos65.target1 --portal "192.168.1.95:3260" --op=update --name node.\
session.auth.password --value=hunter2
[root@server2 iscsi]# iscsiadm -m node --targetname iqn.2014-04.be.linux-tra\
ining:centos65.target1 --portal "192.168.1.95:3260" --op=update --name node.\
session.auth.authmethod --value=CHAP

RHEL and CentOS will store these in /var/lib/iscsi/nodes/.

[root@server2 iscsi]# grep auth /var/lib/iscsi/nodes/iqn.2014-04.be.linux-tr\
aining\:centos65.target1/192.168.1.95\,3260\,1/default 
node.session.auth.authmethod = CHAP
node.session.auth.username = paul
node.session.auth.password = hunter2
node.conn[0].timeo.auth_timeout = 45
[root@server2 iscsi]#

A restart of the iscsi service will add three new devices to our system.

[root@server2 iscsi]# fdisk -l | grep Disk
Disk /dev/sda: 42.9 GB, 42949672960 bytes
Disk identifier: 0x0004f229
Disk /dev/sdb: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdc: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdd: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sde: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/sdf: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/sdg: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/VolGroup-lv_root: 41.4 GB, 41448112128 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/VolGroup-lv_swap: 973 MB, 973078528 bytes
Disk identifier: 0x00000000
[root@server2 iscsi]# service iscsi restart
Stopping iscsi:                                            [  OK  ]
Starting iscsi:                                            [  OK  ]
[root@server2 iscsi]# fdisk -l | grep Disk
Disk /dev/sda: 42.9 GB, 42949672960 bytes
Disk identifier: 0x0004f229
Disk /dev/sdb: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdc: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdd: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sde: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/sdf: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/sdg: 2147 MB, 2147483648 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/VolGroup-lv_root: 41.4 GB, 41448112128 bytes
Disk identifier: 0x00000000
Disk /dev/mapper/VolGroup-lv_swap: 973 MB, 973078528 bytes
Disk identifier: 0x00000000
Disk /dev/sdh: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdi: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000
Disk /dev/sdj: 1073 MB, 1073741824 bytes
Disk identifier: 0x00000000

You can verify iscsi status with:

service iscsi status

iSCSI target on Debian

Installing the software for the target server requires iscsitarget on Ubuntu and Debian, and an extra iscsitarget-dkms for the kernel modules only on Debian.

root@debby6:~# aptitude install iscsitarget
The following NEW packages will be installed:
  iscsitarget 
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 69.4 kB of archives. After unpacking 262 kB will be used.
Get:1 http://ftp.belnet.be/debian/ squeeze/main iscsitarget i386 1.4.20.2-1\
 [69.4 kB]
Fetched 69.4 kB in 0s (415 kB/s)
Selecting previously deselected package iscsitarget.
(Reading database ... 36441 files and directories currently installed.)
Unpacking iscsitarget (from .../iscsitarget_1.4.20.2-1_i386.deb) ...
Processing triggers for man-db ...
Setting up iscsitarget (1.4.20.2-1) ...
iscsitarget not enabled in "/etc/default/iscsitarget", not starting...(warning).

On Debian 6 you will also need aptitude install iscsitarget-dkms for the kernel modules, on Debian 5 this is aptitude install iscsitarget-modules-`uname -a`. Ubuntu includes the kernel modules in the main package.

The iSCSI target server is disabled by default, so we enable it.

root@debby6:~# cat /etc/default/iscsitarget 
ISCSITARGET_ENABLE=false
root@debby6:~# vi /etc/default/iscsitarget 
root@debby6:~# cat /etc/default/iscsitarget 
ISCSITARGET_ENABLE=true

iSCSI target setup with dd files

You can use LVM volumes (/dev/md0/lvol0), physical partitions (/dev/sda) ,raid devices (/dev/md0) or just plain files for storage. In this demo, we use files created with dd.

This screenshot shows how to create three small files (100MB, 200MB and 300MB).

root@debby6:~# mkdir /iscsi
root@debby6:~# dd if=/dev/zero of=/iscsi/lun1.img bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 0.315825 s, 332 MB/s
root@debby6:~# dd if=/dev/zero of=/iscsi/lun2.img bs=1M count=200
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 1.08342 s, 194 MB/s
root@debby6:~# dd if=/dev/zero of=/iscsi/lun3.img bs=1M count=300
300+0 records in
300+0 records out
314572800 bytes (315 MB) copied, 1.36209 s, 231 MB/s

We need to declare these three files as iSCSI targets in /etc/iet/ietd.conf (used to be /etc/ietd.conf).

root@debby6:/etc/iet# cp ietd.conf ietd.conf.original
root@debby6:/etc/iet# > ietd.conf
root@debby6:/etc/iet# vi ietd.conf
root@debby6:/etc/iet# cat ietd.conf
Target iqn.2010-02.be.linux-training:storage.lun1
    IncomingUser isuser hunter2
    OutgoingUser
    Lun 0 Path=/iscsi/lun1.img,Type=fileio
    Alias LUN1

Target iqn.2010-02.be.linux-training:storage.lun2
    IncomingUser isuser hunter2
    OutgoingUser
    Lun 0 Path=/iscsi/lun2.img,Type=fileio
    Alias LUN2

Target iqn.2010-02.be.linux-training:storage.lun3
    IncomingUser isuser hunter2
    OutgoingUser
    Lun 0 Path=/iscsi/lun3.img,Type=fileio
    Alias LUN3

We also need to add our devices to the /etc/initiators.allow file.

root@debby6:/etc/iet# cp initiators.allow initiators.allow.original
root@debby6:/etc/iet# >initiators.allow
root@debby6:/etc/iet# vi initiators.allow
root@debby6:/etc/iet# cat initiators.allow
iqn.2010-02.be.linux-training:storage.lun1
iqn.2010-02.be.linux-training:storage.lun2
iqn.2010-02.be.linux-training:storage.lun3

Time to start the server now:

root@debby6:/etc/iet# /etc/init.d/iscsitarget start
Starting iSCSI enterprise target service:.
.
root@debby6:/etc/iet#

Verify activation of the storage devices in /proc/net/iet:

root@debby6:/etc/iet# cat /proc/net/iet/volume 
tid:3 name:iqn.2010-02.be.linux-training:storage.lun3
    lun:0 state:0 iotype:fileio iomode:wt blocks:614400 blocksize:\
512 path:/iscsi/lun3.img
tid:2 name:iqn.2010-02.be.linux-training:storage.lun2
    lun:0 state:0 iotype:fileio iomode:wt blocks:409600 blocksize:\
512 path:/iscsi/lun2.img
tid:1 name:iqn.2010-02.be.linux-training:storage.lun1
    lun:0 state:0 iotype:fileio iomode:wt blocks:204800 blocksize:\
512 path:/iscsi/lun1.img
root@debby6:/etc/iet# cat /proc/net/iet/session 
tid:3 name:iqn.2010-02.be.linux-training:storage.lun3
tid:2 name:iqn.2010-02.be.linux-training:storage.lun2
tid:1 name:iqn.2010-02.be.linux-training:storage.lun1

ISCSI initiator on ubuntu

First we install the iSCSi client software (on another computer than the target).

root@ubu1104:~# aptitude install open-iscsi
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
The following NEW packages will be installed:
  open-iscsi open-iscsi-utils{a}

Then we set the iSCSI client to start automatically.

root@ubu1104:/etc/iscsi# cp iscsid.conf iscsid.conf.original
root@ubu1104:/etc/iscsi# vi iscsid.conf
root@ubu1104:/etc/iscsi# grep ^node.startup iscsid.conf
node.startup = automatic

Or you could start it manually.

root@ubu1104:/etc/iscsi/nodes# /etc/init.d/open-iscsi start
 * Starting iSCSI initiator service iscsid                        [ OK ] 
 * Setting up iSCSI targets                                       [ OK ] 
root@ubu1104:/etc/iscsi/nodes#

Now we can connect to the Target server and use iscsiadm to discover the devices it offers:

root@ubu1104:/etc/iscsi# iscsiadm  -m discovery -t st -p 192.168.1.31
192.168.1.31:3260,1 iqn.2010-02.be.linux-training:storage.lun2
192.168.1.31:3260,1 iqn.2010-02.be.linux-training:storage.lun1
192.168.1.31:3260,1 iqn.2010-02.be.linux-training:storage.lun3

We can use the same iscsiadm to edit the files in /etc/iscsi/nodes/.

root@ubu1104:/etc/iscsi# iscsiadm -m node --targetname "iqn.2010-02.be.linu\
x-training:storage.lun1" --portal "192.168.1.31:3260" --op=update --name no\
de.session.auth.authmethod --value=CHAP
root@ubu1104:/etc/iscsi# iscsiadm -m node --targetname "iqn.2010-02.be.linu\
x-training:storage.lun1" --portal "192.168.1.31:3260" --op=update --name no\
de.session.auth.username --value=isuser
root@ubu1104:/etc/iscsi# iscsiadm -m node --targetname "iqn.2010-02.be.linu\
x-training:storage.lun1" --portal "192.168.1.31:3260" --op=update --name no\
de.session.auth.password --value=hunter2

Repeat the above for the other two devices.

Restart the initiator service to log in to the target.

root@ubu1104:/etc/iscsi/nodes# /etc/init.d/open-iscsi restart
 * Disconnecting iSCSI targets                                      [ OK ]
 * Stopping iSCSI initiator service                                 [ OK ]
 * Starting iSCSI initiator service iscsid                          [ OK ]
 * Setting up iSCSI targets

Use fdisk -l to enjoy three new iSCSI devices.

root@ubu1104:/etc/iscsi/nodes# fdisk -l 2> /dev/null | grep Disk
Disk /dev/sda: 17.2 GB, 17179869184 bytes
Disk identifier: 0x0001983f
Disk /dev/sdb: 209 MB, 209715200 bytes
Disk identifier: 0x00000000
Disk /dev/sdd: 314 MB, 314572800 bytes
Disk identifier: 0x00000000
Disk /dev/sdc: 104 MB, 104857600 bytes
Disk identifier: 0x00000000

The Target (the server) now shows active sessions.

root@debby6:/etc/iet# cat /proc/net/iet/session 
tid:3 name:iqn.2010-02.be.linux-training:storage.lun3
    sid:5348024611832320 initiator:iqn.1993-08.org.debian:01:8983ed2d770
        cid:0 ip:192.168.1.35 state:active hd:none dd:none
tid:2 name:iqn.2010-02.be.linux-training:storage.lun2
    sid:4785074624856576 initiator:iqn.1993-08.org.debian:01:8983ed2d770
        cid:0 ip:192.168.1.35 state:active hd:none dd:none
tid:1 name:iqn.2010-02.be.linux-training:storage.lun1
    sid:5066549618344448 initiator:iqn.1993-08.org.debian:01:8983ed2d770
        cid:0 ip:192.168.1.35 state:active hd:none dd:none
root@debby6:/etc/iet#

using iSCSI devices

There is no difference between using SCSI or iSCSI devices once they are connected : partition, make filesystem, mount.

root@ubu1104:/etc/iscsi/nodes# history | tail -13
   94  fdisk /dev/sdc
   95  fdisk /dev/sdd
   96  fdisk /dev/sdb
   97  mke2fs /dev/sdb1
   98  mke2fs -j /dev/sdc1
   99  mkfs.ext4 /dev/sdd1
  100  mkdir /mnt/is1
  101  mkdir /mnt/is2
  102  mkdir /mnt/is3
  103  mount /dev/sdb1 /mnt/is1
  104  mount /dev/sdc1 /mnt/is2
  105  mount /dev/sdd1 /mnt/is3
  106  history | tail -13
root@ubu1104:/etc/iscsi/nodes# mount | grep is
/dev/sdb1 on /mnt/is1 type ext2 (rw)
/dev/sdc1 on /mnt/is2 type ext3 (rw)
/dev/sdd1 on /mnt/is3 type ext4 (rw)

iSCSI Target RHEL7/CentOS7

The prefered tool to setup an iSCSI Target on RHEL is targetcli.

[root@linux ~]# yum install targetcli
Loaded plugins: fastestmirror
...
...
Installed:
  targetcli.noarch 0:2.1.fb37-3.el7

Complete!
[root@linux ~]#

The targetcli tool is interactive and represents the configuration fo the target in a structure that resembles a directory tree with several files. Although this is explorable inside targetcli with ls, cd and pwd, this are not files on the file system.

This tool also has tab-completion, which is very handy for the iqn names.

[root@linux ~]# targetcli
targetcli shell version 2.1.fb37
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.

/> cd backstores/
/backstores> ls
o- backstores ............................................................ [...]
  o- block ................................................ [Storage Objects: 0]
  o- fileio ............................................... [Storage Objects: 0]
  o- pscsi ................................................ [Storage Objects: 0]
  o- ramdisk .............................................. [Storage Objects: 0]
/backstores> cd block
/backstores/block> ls
o- block .................................................. [Storage Objects: 0]
/backstores/block> create server1.disk1 /dev/sdb
Created block storage object server1.disk1 using /dev/sdb.
/backstores/block> ls
o- block .................................................. [Storage Objects: 1]
  o- server1.disk1 .................. [/dev/sdb (2.0GiB) write-thru deactivated]
/backstores/block> cd /iscsi
/iscsi> create iqn.2015-04.be.linux:iscsi1
Created target iqn.2015-04.be.linux:iscsi1.
Created TPG 1.
Global pref auto_add_default_portal=true
Created default portal listening on all IPs (0.0.0.0), port 3260.
/iscsi> cd /iscsi/iqn.2015-04.be.linux:iscsi1/tpg1/acls
/iscsi/iqn.20...si1/tpg1/acls> create iqn.2015-04.be.linux:server2
Created Node ACL for iqn.2015-04.be.linux:server2
/iscsi/iqn.20...si1/tpg1/acls> cd iqn.2015-04.be.linux:server2
/iscsi/iqn.20...linux:server2> set auth userid=paul
Parameter userid is now 'paul'.
/iscsi/iqn.20...linux:server2> set auth password=hunter2
Parameter password is now 'hunter2'.
/iscsi/iqn.20...linux:server2> cd /iscsi/iqn.2015-04.be.linux:iscsi1/tpg1/luns
/iscsi/iqn.20...si1/tpg1/luns> create /backstores/block/server1.disk1
Created LUN 0.
Created LUN 0->0 mapping in node ACL iqn.2015-04.be.linux:server2
s/scsi/iqn.20...si1/tpg1/luns> cd /iscsi/iqn.2015-04.be.linux:iscsi1/tpg1/portals
/iscsi/iqn.20.../tpg1/portals> create 192.168.1.128
Using default IP port 3260
Could not create NetworkPortal in configFS.
/iscsi/iqn.20.../tpg1/portals> cd /
/> ls
o- / ..................................................................... [...]
  o- backstores .......................................................... [...]
  | o- block .............................................. [Storage Objects: 1]
  | | o- server1.disk1 ................ [/dev/sdb (2.0GiB) write-thru activated]
  | o- fileio ............................................. [Storage Objects: 0]
  | o- pscsi .............................................. [Storage Objects: 0]
  | o- ramdisk ............................................ [Storage Objects: 0]
  o- iscsi ........................................................ [Targets: 1]
  | o- iqn.2015-04.be.linux:iscsi1 ................................... [TPGs: 1]
  |   o- tpg1 ........................................... [no-gen-acls, no-auth]
  |     o- acls ...................................................... [ACLs: 1]
  |     | o- iqn.2015-04.be.linux:server2 ..................... [Mapped LUNs: 1]
  |     |   o- mapped_lun0 ..................... [lun0 block/server1.disk1 (rw)]
  |     o- luns ...................................................... [LUNs: 1]
  |     | o- lun0 ............................. [block/server1.disk1 (/dev/sdb)]
  |     o- portals ................................................ [Portals: 1]
  |       o- 0.0.0.0:3260 ................................................. [OK]
  o- loopback ..................................................... [Targets: 0]
/> saveconfig
Last 10 configs saved in /etc/target/backup.
Configuration saved to /etc/target/saveconfig.json
/> exit
Global pref auto_save_on_exit=true
Last 10 configs saved in /etc/target/backup.
Configuration saved to /etc/target/saveconfig.json
[root@linux ~]#

Use the systemd tools to manage the service:

[root@linux ~]# systemctl enable target
ln -s '/usr/lib/systemd/system/target.service' '/etc/systemd/system/multi-user.target.wants/target.service'
[root@linux ~]# systemctl start target
[root@linux ~]#

Depending on your organisations policy, you may need to configure firewall and SELinux. The screenshot belows adds a firewall rule to allow all traffic over port 3260, and disables SELinux.

[root@linux ~]# firewall-cmd --permanent --add-port=3260/tcp
[root@linux ~]# firewall-cmd --reload
[root@linux ~]# setenforce 0

The total configuration is visible using ls from the root.

[root@linux ~]# targetcli
targetcli shell version 2.1.fb37
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.

/> ls
o- / ..................................................................... [...]
  o- backstores .......................................................... [...]
  | o- block .............................................. [Storage Objects: 1]
  | | o- server1.disk1 ................ [/dev/sdb (2.0GiB) write-thru activated]
  | o- fileio ............................................. [Storage Objects: 0]
  | o- pscsi .............................................. [Storage Objects: 0]
  | o- ramdisk ............................................ [Storage Objects: 0]
  o- iscsi ........................................................ [Targets: 1]
  | o- iqn.2015-04.be.linux:iscsi1 ................................... [TPGs: 1]
  |   o- tpg1 ........................................... [no-gen-acls, no-auth]
  |     o- acls ...................................................... [ACLs: 1]
  |     | o- iqn.2015-04.be.linux:server2 ..................... [Mapped LUNs: 1]
  |     |   o- mapped_lun0 ..................... [lun0 block/server1.disk1 (rw)]
  |     o- luns ...................................................... [LUNs: 1]
  |     | o- lun0 ............................. [block/server1.disk1 (/dev/sdb)]
  |     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
[root@linux ~]#

The iSCSI Target is now ready.

iSCSI Initiator RHEL7/CentOS7

This is identical to the RHEL6/CentOS6 procedure:

[root@linux ~]# yum install iscsi-initiator-utils
Loaded plugins: fastestmirror
...
...
Installed:
  iscsi-initiator-utils.x86_64 0:6.2.0.873-29.el7

Dependency Installed:
  iscsi-initiator-utils-iscsiuio.x86_64 0:6.2.0.873-29.el7

Complete!

Map your initiator name to the targetcli acl.

[root@linux ~]# cat /etc/iscsi/initiatorname.iscsi
InitiatorName=iqn.2015-04.be.linux:server2
[root@linux ~]#

Enter the CHAP authentication in /etc/iscsi/iscsid.conf.

[root@linux ~]# vi /etc/iscsi/iscsid.conf
...
[root@linux ~]# grep ^node.session.auth /etc/iscsi/iscsid.conf
node.session.auth.authmethod = CHAP
node.session.auth.username = paul
node.session.auth.password = hunter2
[root@linux ~]#

There are no extra devices yet...

[root@linux ~]# fdisk -l | grep sd
Disk /dev/sda: 22.0 GB, 22038806528 bytes, 43044544 sectors
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    43042815    21008384   8e  Linux LVM
Disk /dev/sdb: 2147 MB, 2147483648 bytes, 4194304 sectors

Enable the service and discover the target.

[root@linux ~]# systemctl enable iscsid
ln -s '/usr/lib/systemd/system/iscsid.service' '/etc/systemd/system/multi-user.target.wants/iscsid.service'
[root@linux ~]# iscsiadm -m discovery -t st -p 192.168.1.128
192.168.1.128:3260,1 iqn.2015-04.be.linux:iscsi1

Log into the target and see /dev/sdc appear.

[root@linux ~]# iscsiadm -m node -T iqn.2015-04.be.linux:iscsi1 -p 192.168.1.128 -l
Logging in to [iface: default, target: iqn.2015-04.be.linux:iscsi1, portal: 192.168.1.128,3260] (multiple)
Login to [iface: default, target: iqn.2015-04.be.linux:iscsi1, portal: 192.168.1.128,3260] successful.
[root@linux ~]#
[root@linux ~]# fdisk -l | grep sd
Disk /dev/sda: 22.0 GB, 22038806528 bytes, 43044544 sectors
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    43042815    21008384   8e  Linux LVM
Disk /dev/sdb: 2147 MB, 2147483648 bytes, 4194304 sectors
Disk /dev/sdc: 2147 MB, 2147483648 bytes, 4194304 sectors
[root@linux ~]#

practice: iSCSI devices

1. Set up a target (using an LVM and a SCSI device) and an initiator that connects to both.

2. Set up an iSCSI Target and Initiator on two CentOS7/RHEL7 computers with the following information:

variable value

Target Server IP

shared devices on target /dev/sd /dev/sd /dev/sd

shared device name sd

shared device name sd

shared device name sd

target iqn

initiator iqn

username

password

: iSCSI Target and Initiator practice

solution: iSCSI devices

1. Set up a target (using an LVM and a SCSI device) and an initiator that connects to both.

This solution was done on Debian/ubuntu/Mint. For RHEL/CentOS check the theory.

Decide (with a partner) on a computer to be the Target and another computer to be the Initiator.

On the Target computer:

First install iscsitarget using the standard tools for installing software in your distribution. Then use your knowledge from the previous chapter to setup a logical volume (/dev/vg/lvol0) and use the RAID chapter to setup /dev/md0. Then perform the following step:

vi /etc/default/iscsitarget (set enable to true)

Add your devices to /etc/iet/ietf.conf

root@debby6:/etc/iet# cat ietd.conf
Target iqn.2010-02.be.linux-training:storage.lun1
 IncomingUser isuser hunter2
 OutgoingUser
 Lun 0 Path=/dev/vg/lvol0,Type=fileio
 Alias LUN1
Target iqn.2010-02.be.linux-training:storage.lun2
 IncomingUser isuser hunter2
 OutgoingUser
 Lun 0 Path=/dev/md0,Type=fileio
 Alias LUN2

Add both devices to /etc/iet/initiators.allow

root@debby6:/etc/iet# cat initiators.allow
iqn.2010-02.be.linux-training:storage.lun1
iqn.2010-02.be.linux-training:storage.lun2

Now start the iscsitarget daemon and move over to the Initiator.

On the Initiator computer:

Install open-iscsi and start the daemon.

Then use iscsiadm -m discovery -t st -p 'target-ip' to see the iscsi devices on the Target.

Edit the files /etc/iscsi/nodes/ as shown in the book. Then restart the iSCSI daemon and rund fdisk -l to see the iSCSI devices.

2. Set up an iSCSI Target and Initiator on two CentOS7/RHEL7 computers with the following information:

variable value

Target Server IP 192.168.1.143 (Adjust for your subnet!)

shared devices on target /dev/sdb /dev/sdc /dev/sdd

shared device name sdb target.disk1

shared device name sdc target.disk2

shared device name sdd target.disk3

target iqn iqn.2015-04.be.linux:target

initiator iqn iqn.2015-04.be.linux:initiator

username paul

password hunter2

: iSCSI Target and Initiator practice

On the iSCSI Target server:

[root@linux ~]# targetcli
targetcli shell version 2.1.fb37
Copyright 2011-2013 by Datera, Inc and others.
For help on commands, type 'help'.

/> cd /backstores/block
/backstores/block> ls
o- block .................................................. [Storage Objects: 0]
/backstores/block> create target.disk1 /dev/sdb
Created block storage object target.disk1 using /dev/sdb.
/backstores/block> create target.disk2 /dev/sdc
Created block storage object target.disk2 using /dev/sdc.
/backstores/block> create target.disk3 /dev/sdd
Created block storage object target.disk3 using /dev/sdd.
/backstores/block> ls
o- block .................................................. [Storage Objects: 3]
  o- target.disk1 ................... [/dev/sdb (8.0GiB) write-thru deactivated]
  o- target.disk2 ................... [/dev/sdc (8.0GiB) write-thru deactivated]
  o- target.disk3 ................... [/dev/sdd (8.0GiB) write-thru deactivated]
/backstores/block> cd /iscsi
/iscsi> create iqn.2015-04.be.linux:target
Created target iqn.2015-04.be.linux:target.
Created TPG 1.
Global pref auto_add_default_portal=true
Created default portal listening on all IPs (0.0.0.0), port 3260.
/iscsi> cd /iscsi/iqn.2015-04.be.linux:target/tpg1/acls
/iscsi/iqn.20...get/tpg1/acls> create iqn.2015-04.be.linux:initiator
Created Node ACL for iqn.2015-04.be.linux:initiator
/iscsi/iqn.20...get/tpg1/acls> cd iqn.2015-04.be.linux:initiator
/iscsi/iqn.20...nux:initiator> pwd
/iscsi/iqn.2015-04.be.linux:target/tpg1/acls/iqn.2015-04.be.linux:initiator
/iscsi/iqn.20...nux:initiator> set auth userid=paul
Parameter userid is now 'paul'.
/iscsi/iqn.20...nux:initiator> set auth password=hunter2
Parameter password is now 'hunter2'.
/iscsi/iqn.20...nux:initiator> cd /iscsi/iqn.2015-04.be.linux:target/tpg1/
/iscsi/iqn.20...x:target/tpg1> ls
o- tpg1 ................................................. [no-gen-acls, no-auth]
  o- acls ............................................................ [ACLs: 1]
  | o- iqn.2015-04.be.linux:initiator ......................... [Mapped LUNs: 0]
  o- luns ............................................................ [LUNs: 0]
  o- portals ...................................................... [Portals: 1]
    o- 0.0.0.0:3260 ....................................................... [OK]
/iscsi/iqn.20...x:target/tpg1> cd luns
/iscsi/iqn.20...get/tpg1/luns> create /backstores/block/target.disk1
Created LUN 0.
Created LUN 0->0 mapping in node ACL iqn.2015-04.be.linux:initiator
/iscsi/iqn.20...get/tpg1/luns> create /backstores/block/target.disk2
Created LUN 1.
Created LUN 1->1 mapping in node ACL iqn.2015-04.be.linux:initiator
/iscsi/iqn.20...get/tpg1/luns> create /backstores/block/target.disk3
Created LUN 2.
Created LUN 2->2 mapping in node ACL iqn.2015-04.be.linux:initiator
s/scsi/iqn.20...get/tpg1/luns> cd /iscsi/iqn.2015-04.be.linux:target/tpg1/portals
/iscsi/iqn.20.../tpg1/portals> create 192.168.1.143
Using default IP port 3260
Could not create NetworkPortal in configFS.
/iscsi/iqn.20.../tpg1/portals> cd /
/> ls
o- / ..................................................................... [...]
  o- backstores .......................................................... [...]
  | o- block .............................................. [Storage Objects: 3]
  | | o- target.disk1 ................. [/dev/sdb (8.0GiB) write-thru activated]
  | | o- target.disk2 ................. [/dev/sdc (8.0GiB) write-thru activated]
  | | o- target.disk3 ................. [/dev/sdd (8.0GiB) write-thru activated]
  | o- fileio ............................................. [Storage Objects: 0]
  | o- pscsi .............................................. [Storage Objects: 0]
  | o- ramdisk ............................................ [Storage Objects: 0]
  o- iscsi ........................................................ [Targets: 1]
  | o- iqn.2015-04.be.linux:target ................................... [TPGs: 1]
  |   o- tpg1 ........................................... [no-gen-acls, no-auth]
  |     o- acls ...................................................... [ACLs: 1]
  |     | o- iqn.2015-04.be.linux:initiator ................... [Mapped LUNs: 3]
  |     |   o- mapped_lun0 ...................... [lun0 block/target.disk1 (rw)]
  |     |   o- mapped_lun1 ...................... [lun1 block/target.disk2 (rw)]
  |     |   o- mapped_lun2 ...................... [lun2 block/target.disk3 (rw)]
  |     o- luns ...................................................... [LUNs: 3]
  |     | o- lun0 .............................. [block/target.disk1 (/dev/sdb)]
  |     | o- lun1 .............................. [block/target.disk2 (/dev/sdc)]
  |     | o- lun2 .............................. [block/target.disk3 (/dev/sdd)]
  |     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
[root@linux ~]# systemctl enable target
ln -s '/usr/lib/systemd/system/target.service' '/etc/systemd/system/multi-user.target.wants/target.service'
[root@linux ~]# systemctl start target
[root@linux ~]# setenforce 0

On the Initiator:

[root@linux ~]# cat /etc/iscsi/initiatorname.iscsi
InitiatorName=iqn.2015-04.be.linux:initiator
[root@linux ~]# vi /etc/iscsi/iscsid.conf
[root@linux ~]# grep ^node.session.au /etc/iscsi/iscsid.conf
node.session.auth.authmethod = CHAP
node.session.auth.username = paul
node.session.auth.password = hunter2
[root@linux ~]# fdisk -l 2>/dev/null | grep sd
Disk /dev/sda: 22.0 GB, 22038806528 bytes, 43044544 sectors
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    43042815    21008384   8e  Linux LVM
Disk /dev/sdb: 8589 MB, 8589934592 bytes, 16777216 sectors
/dev/sdb1            2048      821247      409600   83  Linux
/dev/sdb2          821248     1640447      409600   83  Linux
/dev/sdb3         1640448     2459647      409600   83  Linux
Disk /dev/sdc: 8589 MB, 8589934592 bytes, 16777216 sectors
Disk /dev/sdd: 8589 MB, 8589934592 bytes, 16777216 sectors
Disk /dev/sde: 2147 MB, 2147483648 bytes, 4194304 sectors
Disk /dev/sdf: 2147 MB, 2147483648 bytes, 4194304 sectors
[root@linux ~]# systemctl enable iscsid
ln -s '/usr/lib/systemd/system/iscsid.service' '/etc/systemd/system/multi-user.target.wants/iscsid.service'
[root@linux ~]# iscsiadm -m node -T iqn.2015-04.be.linux:target -p 192.168.1.143 -l
Logging in to [iface: default, target: iqn.2015-04.be.linux:target, portal: 192.168.1.143,3260] (multiple)
Login to [iface: default, target: iqn.2015-04.be.linux:target, portal: 192.168.1.143,3260] successful.

[root@linux ~]# fdisk -l 2>/dev/null | grep sd
Disk /dev/sda: 22.0 GB, 22038806528 bytes, 43044544 sectors
/dev/sda1   *        2048     1026047      512000   83  Linux
/dev/sda2         1026048    43042815    21008384   8e  Linux LVM
Disk /dev/sdb: 8589 MB, 8589934592 bytes, 16777216 sectors
/dev/sdb1            2048      821247      409600   83  Linux
/dev/sdb2          821248     1640447      409600   83  Linux
/dev/sdb3         1640448     2459647      409600   83  Linux
Disk /dev/sdc: 8589 MB, 8589934592 bytes, 16777216 sectors
Disk /dev/sdd: 8589 MB, 8589934592 bytes, 16777216 sectors
Disk /dev/sde: 2147 MB, 2147483648 bytes, 4194304 sectors
Disk /dev/sdf: 2147 MB, 2147483648 bytes, 4194304 sectors
Disk /dev/sdg: 8589 MB, 8589934592 bytes, 16777216 sectors
Disk /dev/sdh: 8589 MB, 8589934592 bytes, 16777216 sectors
Disk /dev/sdi: 8589 MB, 8589934592 bytes, 16777216 sectors
[root@linux ~]#