Linux iSCSI Target (TCM)

2020-11-11T17:37:45Z

Nirsof: Starting targetcli fail with "g-io-error-quark: Could not connect: No such file or directory" if dbus service is not running. Start dbus before targetcli, and change service order for consistency.

Since kernel 2.6.38 Linux has a new generic Target Core module, merged from LIO [[http://linux-iscsi.org/wiki/Main_Page]], and since 3.1 there is iSCSI support. This how-to quickly explains how to use it.

Install the utilities to configure Target Core:

# apk add targetcli
# rc-update add dbus
# rc-update add targetcli
# service dbus start
# service targetcli start

In contrast with plain text files as usual, all configuration is done in ConfigFS via targetcli shell (you can use tab for command auto-completion and "ls" for inspecting current config):

# targetcli
Welcome to the targetcli shell::
Copyright (c) 2011 by RisingTide Systems LLC.

For help on commands, type 'help'.

/> ls
o- / ..................................................................... [...]
o- backstores .......................................................... [...]
| o- fileio ............................................... [0 Storage Object]
| o- iblock ............................................... [0 Storage Object]
| o- pscsi ................................................ [0 Storage Object]
| o- rd_dr ................................................ [0 Storage Object]
| o- rd_mcp ............................................... [0 Storage Object]
o- ib_srpt ........................................................ [0 Target]
o- iscsi .......................................................... [0 Target]
o- loopback ....................................................... [0 Target]
o- qla2xxx ........................................................ [0 Target]
/>

You can create a file to be exported as a target:

/> cd backstores/fileio
/backstores/fileio> create file_backstore file1 1M
Generating a wwn serial.
Not using buffered mode.
Created fileio file_backstore.
/backstores/fileio>

Or you can use a block device:

/> cd backstores/blockio
/backstores/blockio> create block0 /dev/sda1

You can use any block device, including RAID and LVM2. Now create an iSCSI Target and a Target Portal Group (tpg) (the iqn is automatically created. You can also specify one by hand):

/> cd /iscsi
/iscsi> create
Created target iqn.2003-01.org.linux-iscsi.rtsnode1.x8664:sn.83a8cde7aca8.
Selected TPG Tag 1.
Successfully created TPG 1.

Now you have to tell Target Core to use the previously create backstore for the target now created:

/iscsi> cd iqn.2003-01.org.linux-iscsi.rtsnode1.x8664:sn.83a8cde7aca8/tpg1/luns
../tpg1/luns> create lun=0 storage_object=/backstores/blockio/block0
Successfully created LUN 0.

Now create the iSCSI portal:

../tpg1/luns> cd ../portals
../tpg1/portals> create ip_address=192.168.1.10
Using default IP port 3260
Successfully created network portal 192.168.1.10:3260.

By default authentication is enabled. To disable it:

../tpg1> set attribute authentication=0
Parameter authentication is now '0'.
../tpg1> set attribute generate_node_acls=1
Parameter generate_node_acls is now '1'.

Finally save the configuration:

/> saveconfig
Existing file /etc/target/saveconfig.json backed up to saveconfig.json.backup
Configuration saved to /etc/target/saveconfig.json

For real use, you should always track changes to the saveconfig file and make sure
(there's a flag for it) to not save config if you are in an error situation. By default,
targetcli creates a config backup if you exit, meaning you might lose the working
config at the time. So better to be prepared.
Errors don't simply appear, but i.e. if you're missing a HBA on boot, these settings
will not be loaded and thus not be in the configuration upon save.

[[Category:Storage]]

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Linux iSCSI Target (TCM)