ISCSI Target

With Wikipedia:iSCSI you can access storage over an IP-based network.

The exported storage entity is the target and the importing entity is the initiator.

There are different modules available to set up the target. The SCSI Target Framework (STGT) was the standard before linux 2.6.38. The current standard is the LIO target. The iSCSI Enterprise Target (IET) is an old implementation and SCSI Target Subsystem (SCST) is the successor of IET and was a possible candidate for kernel inclusion before the decision fell for LIO.

There are packages available for LIO, STGT and IET in the AUR (see below).

Setup with LIO

LIO target is included in the kernel since 2.6.38. However, the iSCSI target fabric is included since linux 3.1.

The important kernel modules are target_core_mod and iscsi_target_mod, which should be in the kernel and loaded automatically.

For the userspace utilities you need lio-utils^AUR.

You start LIO target with

# /etc/rc.d/target start

.

This will load needed modules and optionally loads the previously saved iscsi target configuration.

With

# /etc/rc.d/target status

you can show some information about the running configuration.

You can use targetcli to create the whole configuration or you can alternively use the lio utils tcm_* and lio_* directly.

Using targetcli

You have to install targetcli^AUR from AUR and the dependencies. The config shell creates most names and numbers for you automatically, but you can als provide your own settings. At any point in the shell you can type help in order to see what commands you can issue here.

Tip: You can use tab-completion in this shell

After starting the target (see above) you enter the configuration shell with

# targetcli

...
Using iscsi fabric module.
...

In this shell you include a block device (here: /dev/sdc) to use with

/> cd backstores/iblock
/backstores/iblock> create iblock0 /dev/sdc

Note: You can use any block device, also raid and lvm devices. You can also use files when you go to fileio instead of iblock.

You then create an iSCSI Qualified Name (iqn) and a target portal group (tpg) with

...> cd /iscsi
/iscsi> create

Note: With appending an iqn of your choice to create you can keep targetcli from automatically creating an iqn

In order to tell LIO that your block device should get used as backstore for the target you issue

.../tpg1> cd luns
.../tpg1/luns> create /backstores/iblock/iblock0

Then you need to create a portal, making a daemon listen for incoming connections:

.../luns/lun0> cd ../../portals
.../portals> create

Targetcli will tell you the IP and port where LIO is listening for incoming connections. You will need at least the IP for the clients. The port should be the standard port 3260.

In another root shell you issue this command:

# lio_node --disableauth iqn.2003-01.org.linux-iscsi.HOSTNAME.ARCH:sn.SERIAL 1

Instead of iqn.2003-01.org.linux-iscsi.HOSTNAME.ARCH:sn.SERIAL you have to use the iqn that was created for (or by) you. The 1 stands for the 1st tpg, which is called tpg1 in the example.

Warning: With this setting everybody that knows the iqn of one of your clients (initiators) can access the target. This is for testing or home purposes only.

In order for a client/initiator to connect you still need to include the iqn of the initiator in the target configuration:

...> cd ../../acls
.../acls> create iqn.2005-03.org.open-iscsi:SERIAL

Instead of iqn.2005-03.org.open-iscsi:SERIAL you use the iqn of an initiator. You have to do this for every initiator that needs to connect. Targetcli will automatically map the created lun to the newly created acl.

Note: You can change the mapped luns and if the access should be rw or ro. See help create at this point in the targetcli shell.

The last thing you have to do in targetcli when everything works is saving the configuration with:

...> cd /|
/> saveconfig

The will fill the scripts in /etc/target/{lio,tcm}_start.sh. You can now safely start and stop /etc/rc.d/target without losing your configuration.

You might want to include target in your rc.conf#Daemons.

Using (plain) LIO utils

You have to install lio-utils^AUR from AUR and the dependencies (python2).

Upstream Documentation

• targetcli/rtsadmin
• LIO utils

Setup with SCSI Target Framework (STGT)

You will need the Package tgt^AUR from AUR.

External Howto

• Quickstart Guide for STGT for Fedora

This is also linked on the official STGT website.

Setup with iSCSI Enterprise Target (IET)

You will need iscsitarget-kernel^AUR and iscsitarget-usr^AUR from AUR.

Create the Target

Modify /etc/iet/ietd.conf accordingly

Hard Drive Target

Target iqn.2010-06.ServerName:desc
Lun 0 Path=/dev/sdX,Type=blockio

File based Target

Use "dd" to create a file of the required size, this example is 10GB.

dd if=/dev/zero of=/root/os.img bs=1G count=10

Target iqn.2010-06.ServerName:desc
Lun 0 Path=/root/os.img,Type=fileio

Start server services

rc.d start iscsi-target

Also you can "iscsi-target" to DAEMONS in /etc/rc.conf so that it starts up during boot.

See also

• iSCSI Boot Booting Arch Linux with / on an iSCSI target.
• Persistent block device naming in order to use the correct block device for a target