AT the storage client machine, do:

yum install iscsi-initiator-utils

Edit file /etc/iscsi/initiatorname.iscsi to set your name, example:

InitiatorName=iqn.2010-07.com.example:node1

Start the daemon as it is not started by default:

service iscsid start

Import target devices into database:

iscsiadm --mode discovery --type sendtargets --portal 192.168.0.120

# tree /var/lib/iscsi/

/var/lib/iscsi/
|-- ifaces
|-- isns
|-- nodes
|   `-- iqn.2010-07.com.example:storage.disk
|       `-- 192.168.0.120,3260,1
|           `-- default
|-- send_targets
|   `-- 192.168.0.120,3260
|       |-- iqn.2010-07.com.example:storage.disk,192.168.0.120,3260,1,default -> /var/lib/iscsi/nodes/iqn.2010-07.com.example:storage.disk/192.168.0.120,3260,1
|       `-- st_config
|-- slp
`-- static

Note: For debian, the node database is under /etc/iscsi/.

Connect (login) to the target

iscsiadm -m node -T iqn.2010-07.com.example:storage.disk -l

Logging in to [iface: default, target: iqn.2010-07.com.example:storage.disk, portal: 192.168.0.120,3260]
Login to [iface: default, target: iqn.2010-07.com.example:storage.disk, portal: 192.168.0.120,3260]: successful

The disk is connected as /dev/sda. Sample dmesg output:

scsi1 : iSCSI Initiator over TCP/IP
  Vendor: IET       Model: Controller        Rev: 0001
  Type:   RAID                               ANSI SCSI revision: 05
  Vendor: IET       Model: VIRTUAL-DISK      Rev: 0001
  Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sda: 4194104 512-byte hdwr sectors (2147 MB)
sda: Write Protect is off
sda: Mode Sense: 79 00 00 08
SCSI device sda: drive cache: write back
SCSI device sda: 4194104 512-byte hdwr sectors (2147 MB)
sda: Write Protect is off
sda: Mode Sense: 79 00 00 08
scsi 1:0:0:0: Attached scsi generic sg0 type 12
SCSI device sda: drive cache: write back
 sda: sda1
sd 1:0:0:1: Attached scsi disk sda
sd 1:0:0:1: Attached scsi generic sg1 type 0

At the target, check who is connected:

# tgtadm --lld iscsi --mode target --op show

Target 1: iqn.2010-07.com.example:storage.disk
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
        I_T nexus: 1
            Initiator: iqn.2010-07.com.example:node1
            Connection: 0
                IP Address: 192.168.0.101
        I_T nexus: 2
            Initiator: iqn.2010-07.com.example:node2
            Connection: 0
                IP Address: 192.168.0.102
    LUN information:
        LUN: 0
            Type: controller
            SCSI ID: IET     00010000
            SCSI SN: beaf10
            Size: 0 MB
            Online: Yes
            Removable media: No
            Backing store type: rdwr
            Backing store path: None
        LUN: 1
            Type: disk
            SCSI ID: iscsi_lun1
            SCSI SN: ad58f470
            Size: 2147 MB
            Online: Yes
            Removable media: No
            Backing store type: rdwr
            Backing store path: /dev/drbd0
    Account information:
    ACL information:
        192.168.0.0/24