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:
- The SCSI Target Framework (STGT/TGT) 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.
- 1 Setup with LIO Target
- 2 Setup with SCSI Target Framework (STGT/TGT)
- 3 Setup with iSCSI Enterprise Target (IET)
- 4 See also
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: 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.AUR, AUR and AUR. The original AUR[
# systemctl start target
This will load necessary modules, mount the configfs and load previously saved iscsi target configuration.With
# targetcli statusyou 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).
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.
cdin this shell to view & select paths
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
...> cd /iscsi
createyou 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
cdto 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
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
iqn.2005-03.org.open-iscsi:SERIAL you use the iqn of an initiator.
It can normally be found in
You have to do this for every initiator that needs to connect.
Targetcli will automatically map the created lun to the newly created acl.
help createat 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
You can now safely start and stop
target.service without losing your configuration.
saveconfigand also clear a configuration with
Authentication per CHAP is enabled per default for your targets. You can either setup passwords or disable this authentication.
Navigate targetcli to your target (i.e. /iscsi/iqn.../tpg1) and
.../tpg1> set attribute authentication=0
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
Tips & Tricks
targetcli sessionsyou can list the current open sessions. This command is included in the AUR package, but not in lio-utils or the original targetcli.
Setup with SCSI Target Framework (STGT/TGT)
You will need the Package AUR.AUR from
See: TGT iSCSI Target
Setup with iSCSI Enterprise Target (IET)
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.