FILEIO¶

Allows files to be treated as disk images. When storage objects of this type are created, they can support either write-back or write-thru operation. Using write-back enables the local filesystem cache, which will improve performance but increase the risk of data loss. It is also possible to use fileio with local block device files, if buffered operation is needed.

Fileio also supports using an existing file, or creating a new file. New files are sparsely allocated by default.

BLOCK¶

Allows a local disk block device to be shared.

PSCSI¶

Allows a local SCSI device of any type to be shared. It is generally advised to prefer the block backstore if sharing a block SCSI device is desired.

RAMDISK¶

Allows kernel memory to be shared as a block SCSI device. Since memory is volatile, the contents of the ramdisk will be lost if the system restarts, and this backstore is best used for testing only.

It also supports "nullio" mode, which is not backed by any storage. It discards all writes, and returns all-zeroes for reads.

USERSPACE-BACKED¶

Backstores starting with "user:" are not supported in the kernel, but rely on a userspace process to handle requests. See tcmu-runner(8) for more information on creating backstores of this type.

CREATING A TARGET¶

Use the create command within a fabric's node to create a target. If the fabric's targets are tied to hardware then targetcli will constrain the WWN to available hardware WWNs. These can be shown via tab-completion. If the fabric is not tied to hardware, such as iSCSI, then targetcli will either auto-generate a WWN if none is given, or check that the given WWN has the correct format. All WWNs are prefaced by their type, such as "iqn", "naa", or "ib", and may be given with or without colons.

iSCSI supports multiple WWN formats: iqn, naa, and eui. Other fabrics support single formats only.

TPGS¶

TPGs (Target Portal Groups) allow the iSCSI to support multiple complete configurations within one target. This is useful for complex quality-of-service configurations. targetcli will automatically create one TPG when the target is created, and almost all setups only need one.

PORTALS¶

An iSCSI target may be reached via multiple IP addresses and ports. These addr:port pairs are called portals. Both IPv4 and IPv6 addresses are supported.

When a target is created, targetcli automatically creates a default portal listening on all IPv4 addresses (shown as 0.0.0.0) on port 3260. If a different configuration is needed, the default portal can be removed and portals configured as desired.

If the hardware supports it, iSER (iSCSI Extensions for RDMA) may be enabled via the enable_iser command within each portal's node. Or, if the hardware supports it, hardware offload may be enabled via the enable_offload command within each portal's node.

LUNS¶

The kernel target exports SCSI Logical Units, also called LUNs. This section links the previously-defined storage objects with the target, and defines which number (the Logical Unit Number) the device will use. Note that if ACLs are being used, a lun mapping must be created under the ACL that refers back to the TPG LUN.

ACLS¶

ACLs (Access Control Lists) allow different configuration, depending on the initiator that is connecting to the target. This includes both per-initiator authentication settings as well as per-initiator LUN mappings.

create <wwn> in the acls node creates an ACL for an initiator, and create within the ACL creates a LUN mapping. (This can either refer to the TPG LUN, or to the storage object, in which case the TPG LUN will be configured as well.) Global setting auto_add_mapped_luns affects this, see below.

AUTHENTICATION¶

iSCSI supports authentication via the CHAP protocol, which uses a username and password. The initiator may be required to supply valid credentials to the target, and the target may also be required to supply credentials back to the initiator. The latter is referred to as mutual authentication.

Furthermore, authentication credentials may be different for each session phase (Discovery or Normal), and authentication in a Normal session may be set at the TPG level, or per-ACL.

Discovery Authentication
iSCSI Discovery sessions allow the initiator to connect to a portal and discover targets with the SendTargets command, but not access them. The four parameters userid, password, mutual_userid, and mutual_password are configured via set discovery_auth command within the top-level iscsi configuration node. 1-way authentication is enabled if userid and password are both set, and mutual authentication is enabled if all four are set. Authentication is disabled by unsetting the parameters.

Normal Authentication
Similarly, the four parameters userid, password, mutual_userid, and mutual_password are configured via set auth command within the TPG node and ACL nodes. However, LIO only uses one or the other, depending on the TPG's generate_node_acls attribute setting. If generate_node_acls is 1, the TPG-wide settings will be used. If generate_node_acls is 0, then the user-created ACLs' settings will be used.

Enable generate_node_acls with set attribute generate_node_acls=1 within the TPG node. This can be thought of as "ignore ACLs mode" -- both authentication and LUN mapping will then use the TPG settings.

No Authentication
Authentication is disabled by clearing the TPG "authentication" attribute: set attribute authentication=0. Although initiator names are trivially forgeable, generate_node_acls still works here to either ignore user-defined ACLs and allow all, or check that an ACL exists for the connecting initiator.

DEFINING A STORAGE OBJECT WITHIN A BACKSTORE¶

backstores/fileio create disk1 /disks/disk1.img 140M
Creates a storage object named disk1 with the given path and size. targetcli supports common size abbreviations like 'M', 'G', and 'T'.

EXPORTING A STORAGE OBJECT VIA ISCSI¶

iscsi/ create
Creates an iSCSI target with a default WWN. It will also create an initial target portal group called tpg1.

iqn.2003-01.org.linux-iscsi.test2.x8664:sn123456789012/tpg1/
An example of changing to the configuration node for the given target's first target portal group (TPG). This is equivalent to giving the command prefixed by "cd". (Although more can be useful for certain setups, most configurations have a single TPG per target. In this case, configuring the TPG is equivalent to configuring the overall target.)

portals/ create
Add a portal, i.e. an IP address and TCP port via which the target can be contacted by initiators. Only required if the default 0.0.0.0:3260 portal is not present.

luns/ create /backstores/fileio/disk1
Create a new LUN in the TPG, attached to the storage object that has previously been defined. The storage object now shows up under the /backstores configuration node as activated.

acls/ create iqn.1994-05.com.redhat:4321576890
Creates an ACL (access control list) entry for the given iSCSI initiator.

acls/iqn.1994-05.com.redhat:4321576890 create 2 0
Gives the initiator access to the first exported LUN (lun0), which the initiator will see as lun2. The default is to give the initiator read/write access; if read-only access was desired, an additional "1" argument would be added to enable write-protect. (Note: if global setting auto_add_mapped_luns is true, this step is not necessary.)

EXPORTING A STORAGE OBJECT VIA FCOE¶

tcm_fc/ create 20:00:00:19:99:a8:34:bc
Create an FCoE target with the given WWN. targetcli can tab-complete the WWN based on registered FCoE interfaces. If none are found, verify that they are properly configured and are shown in the output of fcoeadm -i.

tcm_fc/20:00:00:19:99:a8:34:bc/
If auto_cd_after_create is set to false, change to the configuration node for the given target, equivalent to giving the command prefixed by cd.

luns/ create /backstores/fileio/disk1
Create a new LUN for the interface, attached to a previously defined storage object. The storage object now shows up under the /backstores configuration node as activated.

acls/ create 00:99:88:77:66:55:44:33
Create an ACL (access control list), for defining the resources each initiator may access. The default behavior is to auto-map existing LUNs to the ACL; see help for more information.

The LUN should now be accessible via FCoE.

GLOBAL¶

Shell-related user-specific settings are in global, and are visible from all configuration nodes. They are mostly shell display options, but some starting with auto_ affect shell behavior and may merit customization. These include auto_save_on_exit, which controls if exiting targetcli saves the configuration; auto_add_mapped_luns, to automatically add existing LUNs to new ACLs, and new LUNS to existing ACLs; and auto_cd_after_create, to change working path to newly-created nodes. Global settings are user-specific and are saved to ~/.targetcli/ upon exit, unlike other groups, which are system-wide and kept in /etc/target/saveconfig.json.

BACKSTORE-SPECIFIC¶

attribute
/backstore/<type>/<name> configuration node. Contains values relating to the backstore and storage object.

ISCSI-SPECIFIC¶

discovery_auth
/iscsi configuration node. Set the normal and mutual authentication userid and password for discovery sessions, as well as enabling or disabling it. By default it is disabled -- no authentication is required for discovery.

parameter
/iscsi/<target_iqn>/tpgX configuration node. ISCSI-specific parameters such as AuthMethod, MaxBurstLength, IFMarker, DataDigest, and similar.

attribute
/iscsi/<target_iqn>/tpgX configuration node. Contains implementation-specific settings for the TPG, such as authentication, to enforce or disable authentication for the full-feature phase (i.e. non-discovery).

auth
/iscsi/<target_iqn>/tpgX/acls/<initiator_iqn> configuration node. Set the userid and password for full-feature phase for this ACL.

TARGETCLI_HOME¶

If set, this variable points to a directory that should be used instead of ~/.targetcli