Install the iscsi-initiator-utils package:

# yum install iscsi-initiator-utils

Use the SendTargets discovery method to discover the iSCSI targets at a specified IP address:

# iscsiadm -m discovery --type sendtargets -p 10.150.30.72
Starting iscsid:                               [ OK ]
10.150.30.72:3260,1 iqn.2012-01.com.mydom.host01:target1
10.150.30.72:3260,1 iqn.2012-01.com.mydom.host01:target2

The command also starts the iscsid service if it is not already running.

The following command displays information about the targets that is now stored in the discovery database:

# iscsiadm -m discoverydb -t st -p 10.150.30.72
# BEGIN RECORD 2.0-872.41.el6
discovery.startup = manual
discovery.type = sendtargets
discovery.sendtargets.address = 10.150.30.72
discovery.sendtargets.port = 3260
discovery.sendtargets.auth.authmethod = None
discovery.sendtargets.auth.username_in = <empty>
discovery.sendtargets.auth.password_in = <empty>
discovery.sendtargets.timeo.login_timeout = 15
discovery.sendtargets.use_discoveryd = No
discovery.sendtargets.discoveryd_poll_inval = 30
discovery.sendtargets.repoen_max = 5
discovery.sendtargets.timeo.auth_timeout = 45
discovery.sendtargets.timeo.active_timeout = 30
discovery.sendtargets.iscsi.MaxRecvDataSegmentLength = 32768

Establish a session and log in to a specific target:

# iscsiadm -m node --targetname iqn.2012-01.com.mydom.host01:target1 \
  -p 10.150.30.72:3260 -l
Login to [iface: default, target: iqn.2012-01.com.mydom.host01:target1, 
portal: 10.150.30.72:3260] successful.

Verify that the session is active, and display the available LUNs:

# iscsiadm -m session -P 3
Target: iqn.2012-01.com.mydom.host01:target1
Current Portal: 10.150.30.72:3260,1
Persistent Portal: 10.150.30.72:3260,1
**********
Interface:
**********
Iface Name: default
Iface Transport: tcp
Iface Initiatorname: iqn.1988-12.com.mydom:392a7cee2f
Iface IPaddress: 192.0.2.101
Iface HWaddress: <empty>
Iface Netdev: <empty>
SID: 1
iSCSI Connection State: LOGGED IN
iSCSI Session State: LOGGED IN
Internal iscsid Session State: NO CHANGE
.
.
.
************************
Attached SCSI devices:
************************
Host Number: 4 State: running
scsi10 Channel 00 Id 0 Lun:0
scsi10 Channel 00 Id 0 Lun:1
    Attached scsi disk sdb
State: running
scsi10 Channel 00 Id 0 Lun:2
    Attached scsi disk sdc
State: running

The LUNs are represented as SCSI block devices (sd*) in the local /dev directory, for example:

# fdisk -l | grep /dev/sd[bc]
Disk /dev/sdb: 10.7 GB, 10737418240 bytes
Disk /dev/sdc: 10.7 GB, 10737418240 bytes

To distinguish between target LUNs, examine their paths under /dev/disk/by-path:

# ls -l /dev/disk/by-path/
lrwxrwxrwx  1 root root  9 May 15 21:05
  ip-10.150.30.72:3260-iscsi-iqn.2012-01.com.mydom.host01:02:
  084591f8-6b8b-c857-f002-ecf8a3b387f3-lun-1 -> ../../sdb
lrwxrwxrwx 1 root root  9 May 15 21:05
  ip-10.150.30.72:3260-iscsi-iqn.2012-01.com.mydom.host01:02:
  084591f8-6b8b-c857-f002-ecf8a3b387f3-lun-2 -> ../../sdc

You can view the initialization messages for the LUNs in the /var/log/messages file:

# grep -i scsi /var/log/messages
Apr 8 15:08:53 host02 kernel: scsi12 : iSCSI Initiator over TCP/IP
Apr 8 15:08:53 host02 kernel: sd 4:0:0:1: [sdb] Attached SCSI disk
Apr 8 15:08:53 host02 kernel: sd 4:0:0:2: [sdc] Attached SCSI disk

You can configure and use a LUN in the same way as you would any other physical storage device. For example, you can configure it as an LVM physical volume, file system, swap partition, Automatic Storage Management (ASM) disk, or raw device.

Specify the _netdev option when creating mount entries for iSCSI LUNs in /etc/fstab, for example:

UUID=084591f8-6b8b-c857-f002-ecf8a3b387f3     /iscsi_mount_point     ext4     _netdev   0  0

This option indicates the file system resides on a device that requires network access, and prevents the system from attempting to mount the file system until the network has been enabled.