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Configure iSCSI initiator in CentOS

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Below are my notes for configuring a CentOS box to connect to an iSCSI target. This assumes you have already configured an iSCSI target on another machine / NAS. Much of this information comes thanks to this very helpful website.

Install the software package

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yum -y install iscsi-initiator-utils

Configure the iqn name for the initiator

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vi /etc/iscsi/initiatorname.iscsi
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InitiatorName=iqn.2012-10.net.cpd:san.initiator01
InitiatorAlias=initiator01

Edit the iSCSI initiator configuration

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vi /etc/iscsi/iscsid.conf
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node.startup = automatic
node.session.auth.authmethod = CHAP
node.session.auth.username = initiator_user
node.session.auth.password = initiator_pass
#The next two lines are for mutual CHAP authentication
node.session.auth.username_in = target_user
node.session.auth.password_in = target_password

Start iSCSI initiator daemon

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/etc/init.d/iscsid start
chkconfig --levels 235 iscsid on

Discover targets in the iSCSI server:

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iscsiadm --mode discovery -t sendtargets --portal 172.16.201.200 the portal's IP address
172.16.201.200:3260,1 iqn.2012-10.net.cpd:san.target01

Try to log in with the iSCSI LUN:

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iscsiadm --mode node --targetname iqn.2012-10.net.cpd:san.target01 --portal 172.16.201.200 --login
Logging in to [iface: default, target: iqn.2012-10.net.cpd:san.target01, portal: 172.16.201.200,3260] (multiple)
Login to [iface: default, target: iqn.2012-10.net.cpd:san.target01, portal: 172.16.201.200,3260] successful.

Verify configuration

This command shows what is put into the  iSCSI targets database  (the files located in /var/lib/iscsi/)

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cat /var/lib/iscsi/send_targets/172.16.201.200,3260/st_config
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discovery.startup = manual
discovery.type = sendtargets
discovery.sendtargets.address = 172.16.201.200
discovery.sendtargets.port = 3260
discovery.sendtargets.auth.authmethod = None
discovery.sendtargets.timeo.login_timeout = 15
discovery.sendtargets.use_discoveryd = No
discovery.sendtargets.discoveryd_poll_inval = 30
discovery.sendtargets.reopen_max = 5
discovery.sendtargets.timeo.auth_timeout = 45
discovery.sendtargets.timeo.active_timeout = 30
discovery.sendtargets.iscsi.MaxRecvDataSegmentLength = 32768

Verify session is established

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iscsiadm --mode session --op show
tcp: [2] 172.16.201.200:3260,1 iqn.2012-10.net.cpd:san.target01

Create LVM volume and mount

Add our iSCSI disk to a new LVM physical volume, volume group, and logical volume

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fdisk -l
Disk /dev/sdb: 17.2 GB, 17171480576 bytes
64 heads, 32 sectors/track, 16376 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
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Disk /dev/sdb doesn't contain a valid partition table
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pvcreate /dev/sdb
vgcreate iSCSI /dev/sdb
lvcreate iSCSI -n volume_name -l100%FREE
mkfs.ext4 /dev/iSCSI/volume_name

Add the logical volume to fstab

Make sure to use the mount option _netdev.  Without this option, Linux will try to mount this device before it loads network support.

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vi /etc/fstab
/dev/mapper/iSCSI-volume_name    /mnt   ext4   _netdev  0 0

Success.