ISCSI Target

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With 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:

Setup with LIO Target

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.

It is highly recommended to use the free branch versions of the packages: targetcli-fbAUR, python-rtslib-fbAUR and python-configshell-fbAUR. The original targetcliAUR[broken link: archived in aur-mirror] is also available but has a different way of saving the configuration using the deprecated lio-utils and depends on epydoc.

A systemd target.service is included in python-rtslib-fbAUR when you use the free branch and a /etc/rc.d/target in lio-utilsAUR[broken link: archived in aur-mirror] when you use the original targetcli or lio-utils directly.

You start LIO target with
# systemctl start target

This will load necessary modules, mount the configfs and load previously saved iscsi target configuration.

With
# targetcli status
you can show some information about the running configuration (only with the free branch). You might want to enable the lio target on boot with
# systemctl enable target

You can use targetcli to create the whole configuration or you can alternatively use the lio utils tcm_* and lio_* directly (deprecated).

Using targetcli

The external manual is only available in the free branch. targetd is not in AUR yet, but this depends on the free branch.

The config shell creates most names and numbers for you automatically, but you can also 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
Tip: You can type cd in this shell to view & select paths
After starting the target (see above) you enter the configuration shell with
# targetcli

In this shell you include a block device (here: /dev/disk/by-id/md-name-nas:iscsi) to use with

/> cd backstores/block
/backstores/block> create md_block0 /dev/disk/by-id/md-name-nas:iscsi
Note: You can use any block device, also raid and lvm devices. You can also use files when you go to fileio instead of block.
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

Note: Remember that you can type cd to select the path of your <iqn>/tpg1
.../tpg1> cd luns
.../tpg1/luns> create /backstores/block/md_block0

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 (defaults to 0.0.0.0 (all)). You will need at least the IP for the clients. The port should be the standard port 3260.

In order for a client/initiator to connect you 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. It can normally be found in /etc/iscsi/initiatorname.iscsi. 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 whether 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 the configuration in /etc/target/saveconfig.json. You can now safely start and stop target.service without losing your configuration.

Tip: You can give a filename as a parameter to saveconfig and also clear a configuration with clearconfig

Authentication

Authentication per CHAP is enabled per default for your targets. You can either setup passwords or disable this authentication.

Disable Authentication

Navigate targetcli to your target (i.e. /iscsi/iqn.../tpg1) and

.../tpg1> set attribute authentication=0
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.
Set Credentials

Navigate to a certain acl of your target (i.e. /iscsi/iqn.../tpg1/acls/iqn.../) and

...> get auth

will show you the current authentication credentials.

...> set auth userid=<username in target>
...> set auth password=<password in target>
...> set auth mutual_userid=<username in initiator>  (optional)
...> set auth mutual_password=<password in initiator>  (optional)

The first two fields are the username and password of the target. The initiator will use this to log into the target. The last two fields (prefixed with "mutual_") are the username and password of the initiators (note that all initiators will have the same username and password). These two are optional parameters and it ensures that initiators will only accept connections from permitted targets.

Using (plain) LIO utils

You have to install lio-utilsAUR[broken link: archived in aur-mirror] from AUR and the dependencies (python2).

Tips & Tricks

  • With targetcli sessions you can list the current open sessions. This command is included in the targetcli-fbAUR package, but not in lio-utils or the original targetcli.

Upstream Documentation

Setup with SCSI Target Framework (STGT/TGT)

You will need the Package tgtAUR from AUR.

See: TGT iSCSI Target

Setup with iSCSI Enterprise Target (IET)

You will need iscsitarget-kernelAUR[broken link: archived in aur-mirror] and iscsitarget-usrAUR[broken link: archived in aur-mirror] 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

Tango-view-refresh-red.pngThis article or section is out of date.Tango-view-refresh-red.png

Reason: Mentions rc.d scripts and rc.conf. (Discuss in Talk:ISCSI Target#)
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