Chapter 9. Configuring an iSCSI target

Red Hat Enterprise Linux uses the targetcli shell as a command-line interface to perform the following operations:

Add, remove, view, and monitor iSCSI storage interconnects to utilize iSCSI hardware.
Export local storage resources that are backed by either files, volumes, local SCSI devices, or by RAM disks to remote systems.

The targetcli tool has a tree-based layout including built-in tab completion, auto-complete support, and inline documentation.

9.1. Installing targetcli

Install the targetcli tool to add, monitor, and remove iSCSI storage interconnects .

Procedure

Install the targetcli tool:
```
# yum install targetcli
```
Start the target service:
```
# systemctl start target
```
Configure target to start at boot time:
```
# systemctl enable target
```

Open port 3260 in the firewall and reload the firewall configuration:

# firewall-cmd --permanent --add-port=3260/tcp
Success

# firewall-cmd --reload
Success

Verification

View the targetcli layout:

# targetcli
/> ls
o- /........................................[...]
  o- backstores.............................[...]
  | o- block.................[Storage Objects: 0]
  | o- fileio................[Storage Objects: 0]
  | o- pscsi.................[Storage Objects: 0]
  | o- ramdisk...............[Storage Objects: 0]
  o- iscsi...........................[Targets: 0]
  o- loopback........................[Targets: 0]

Additional resources

targetcli(8) man page

9.2. Creating an iSCSI target

Creating an iSCSI target enables the iSCSI initiator of the client to access the storage devices on the server. Both targets and initiators have unique identifying names.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.

Procedure

Navigate to the iSCSI directory:
```
/> iscsi/
```
Note
The cd command is used to change directories as well as to list the path to move into.

Use one of the following options to create an iSCSI target:

Creating an iSCSI target using a default target name:

/iscsi> create

Created target
iqn.2003-01.org.linux-iscsi.hostname.x8664:sn.78b473f296ff
Created TPG1

Creating an iSCSI target using a specific name:

/iscsi> create iqn.2006-04.com.example:444

Created target iqn.2006-04.com.example:444
Created TPG1
Here iqn.2006-04.com.example:444 is target_iqn_name

Replace iqn.2006-04.com.example:444 with the specific target name.

Verify the newly created target:

/iscsi> ls

o- iscsi.......................................[1 Target]
    o- iqn.2006-04.com.example:444................[1 TPG]
        o- tpg1...........................[enabled, auth]
           o- acls...............................[0 ACL]
            o- luns...............................[0 LUN]
           o- portals.........................[0 Portal]

Additional resources

targetcli(8) man page

9.3. iSCSI Backstore

An iSCSI backstore enables support for different methods of storing an exported LUN’s data on the local machine. Creating a storage object defines the resources that the backstore uses.

An administrator can choose any of the following backstore devices that Linux-IO (LIO) supports:

fileio backstore: Create a fileio storage object if you are using regular files on the local file system as disk images. For creating a fileio backstore, see Creating a fileio storage object.
block backstore: Create a block storage object if you are using any local block device and logical device. For creating a block backstore, see Creating a block storage object.
pscsi backstore: Create a pscsi storage object if your storage object supports direct pass-through of SCSI commands. For creating a pscsi backstore, see Creating a pscsi storage object.
ramdisk backstore: Create a ramdisk storage object if you want to create a temporary RAM backed device. For creating a ramdisk backstore, see Creating a Memory Copy RAM disk storage object.

Additional resources

targetcli(8) man page

9.4. Creating a fileio storage object

fileio storage objects can support either the write_back or write_thru operations. The write_back operation enables the local file system cache. This improves performance but increases the risk of data loss.

It is recommended to use write_back=false to disable the write_back operation in favor of the write_thru operation.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.

Procedure

Navigate to the fileio/ from the backstores/ directory:
```
/> backstores/fileio
```

Create a fileio storage object:

/backstores/fileio> create file1 /tmp/disk1.img 200M write_back=false

Created fileio file1 with size 209715200

Verification

Verify the created fileio storage object:
```
/backstores/fileio> ls
```

Additional resources

targetcli(8) man page

9.5. Creating a block storage object

The block driver allows the use of any block device that appears in the /sys/block/ directory to be used with Linux-IO (LIO). This includes physical devices such as, HDDs, SSDs, CDs, and DVDs, and logical devices such as, software or hardware RAID volumes, or LVM volumes.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.

Procedure

Navigate to the block/ from the backstores/ directory:
```
/> backstores/block/
```

Create a block backstore:

/backstores/block> create name=block_backend dev=/dev/sdb

Generating a wwn serial.
Created block storage object block_backend using /dev/vdb.

Verification

Verify the created block storage object:
```
/backstores/block> ls
```
Note
You can also create a block backstore on a logical volume.

Additional resources

targetcli(8) man page

9.6. Creating a pscsi storage object

You can configure, as a backstore, any storage object that supports direct pass-through of SCSI commands without SCSI emulation, and with an underlying SCSI device that appears with lsscsi in the /proc/scsi/scsi such as, a SAS hard drive . SCSI-3 and higher is supported with this subsystem.

Warning

pscsi should only be used by advanced users. Advanced SCSI commands such as for Asymmetric Logical Unit Assignment (ALUAs) or Persistent Reservations (for example, those used by VMware ESX, and vSphere) are usually not implemented in the device firmware and can cause malfunctions or crashes. When in doubt, use block backstore for production setups instead.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.

Procedure

Navigate to the pscsi/ from the backstores/ directory:
```
/> backstores/pscsi/
```

Create a pscsi backstore for a physical SCSI device, a TYPE_ROM device using /dev/sr0 in this example:

/backstores/pscsi> create name=pscsi_backend dev=/dev/sr0

Generating a wwn serial.
Created pscsi storage object pscsi_backend using /dev/sr0

Verification

Verify the created pscsi storage object:
```
/backstores/pscsi> ls
```

Additional resources

targetcli(8) man page

9.7. Creating a Memory Copy RAM disk storage object

Memory Copy RAM disks (ramdisk) provide RAM disks with full SCSI emulation and separate memory mappings using memory copy for initiators. This provides capability for multi-sessions and is particularly useful for fast and volatile mass storage for production purposes.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.

Procedure

Navigate to the ramdisk/ from the backstores/ directory:
```
/> backstores/ramdisk/
```

Create a 1GB RAM disk backstore:

/backstores/ramdisk> create name=rd_backend size=1GB

Generating a wwn serial.
Created rd_mcp ramdisk rd_backend with size 1GB.

Verification

Verify the created ramdisk storage object:
```
/backstores/ramdisk> ls
```

Additional resources

targetcli(8) man page

9.8. Creating an iSCSI portal

Creating an iSCSI portal adds an IP address and a port to the target that keeps the target enabled.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.
An iSCSI target associated with a Target Portal Groups (TPG). For more information, see Creating an iSCSI target.

Procedure

Navigate to the TPG directory:
```
/iscsi> iqn.2006-04.example:444/tpg1/
```
Use one of the following options to create an iSCSI portal:
1. Creating a default portal uses the default iSCSI port 3260 and allows the target to listen to all IP addresses on that port:
```
/iscsi/iqn.20...mple:444/tpg1> portals/ create

Using default IP port 3260
Binding to INADDR_Any (0.0.0.0)
Created network portal 0.0.0.0:3260
```
  Note
  When an iSCSI target is created, a default portal is also created. This portal is set to listen to all IP addresses with the default port number that is: 0.0.0.0:3260.
  To remove the default portal, use the following command:
  /iscsi/iqn-name/tpg1/portals delete ip_address=0.0.0.0 ip_port=3260
2. Creating a portal using a specific IP address:
```
/iscsi/iqn.20...mple:444/tpg1> portals/ create 192.168.122.137

Using default IP port 3260
Created network portal 192.168.122.137:3260
```

Verification

Verify the newly created portal:

/iscsi/iqn.20...mple:444/tpg1> ls

o- tpg.................................. [enambled, auth]
    o- acls ......................................[0 ACL]
    o- luns ......................................[0 LUN]
    o- portals ................................[1 Portal]
       o- 192.168.122.137:3260......................[OK]

Additional resources

targetcli(8) man page

9.9. Creating an iSCSI LUN

Logical unit number (LUN) is a physical device that is backed by the iSCSI backstore. Each LUN has a unique number.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.
An iSCSI target associated with a Target Portal Groups (TPG). For more information, see Creating an iSCSI target.
Created storage objects. For more information, see iSCSI Backstore.

Procedure

Create LUNs of already created storage objects:

/iscsi/iqn.20...mple:444/tpg1> luns/ create /backstores/ramdisk/rd_backend
Created LUN 0.

/iscsi/iqn.20...mple:444/tpg1> luns/ create /backstores/block/block_backend
Created LUN 1.

/iscsi/iqn.20...mple:444/tpg1> luns/ create /backstores/fileio/file1
Created LUN 2.

Verify the created LUNs:

/iscsi/iqn.20...mple:444/tpg1> ls

o- tpg.................................. [enambled, auth]
    o- acls ......................................[0 ACL]
    o- luns .....................................[3 LUNs]
    |  o- lun0.........................[ramdisk/ramdisk1]
    |  o- lun1.................[block/block1 (/dev/vdb1)]
    |  o- lun2...................[fileio/file1 (/foo.img)]
    o- portals ................................[1 Portal]
        o- 192.168.122.137:3260......................[OK]

Default LUN name starts at 0.

Important

By default, LUNs are created with read-write permissions. If a new LUN is added after ACLs are created, LUN automatically maps to all available ACLs and can cause a security risk. To create a LUN with read-only permissions, see Creating a read-only iSCSI LUN.

Configure ACLs. For more information, see Creating an iSCSI ACL.

Additional resources

targetcli(8) man page

9.10. Creating a read-only iSCSI LUN

By default, LUNs are created with read-write permissions. This procedure describes how to create a read-only LUN.

Prerequisites

Installed and running targetcli. For more information, see Installing targetcli.
An iSCSI target associated with a Target Portal Groups (TPG). For more information, see Creating an iSCSI target.
Created storage objects. For more information, see iSCSI Backstore.

Procedure

Set read-only permissions:
```
/> set global auto_add_mapped_luns=false

Parameter auto_add_mapped_luns is now 'false'.
```
This prevents the auto mapping of LUNs to existing ACLs allowing the manual mapping of LUNs.

Navigate to the initiator_iqn_name directory:

/> iscsi/target_iqn_name/tpg1/acls/initiator_iqn_name/

Create the LUN:

/iscsi/target_iqn_name/tpg1/acls/initiator_iqn_name> create mapped_lun=next_sequential_LUN_number tpg_lun_or_backstore=backstore write_protect=1

Example:

/iscsi/target_iqn_name/tpg1/acls/2006-04.com.example:888> create mapped_lun=1 tpg_lun_or_backstore=/backstores/block/block2 write_protect=1

Created LUN 1.
Created Mapped LUN 1.

Verify the created LUN:

/iscsi/target_iqn_name/tpg1/acls/2006-04.com.example:888> ls
 o- 2006-04.com.example:888 .. [Mapped LUNs: 2]
 | o- mapped_lun0 .............. [lun0 block/disk1 (rw)]
 | o- mapped_lun1 .............. [lun1 block/disk2 (ro)]

The mapped_lun1 line now has (ro) at the end (unlike mapped_lun0’s (rw)) stating that it is read-only.

Configure ACLs. For more information, see Creating an iSCSI ACL.

Additional resources

targetcli(8) man page

9.11. Creating an iSCSI ACL

The targetcli service uses Access Control Lists (ACLs) to define access rules and grant each initiator access to a Logical Unit Number (LUN).

Both targets and initiators have unique identifying names. You must know the unique name of the initiator to configure ACLs. The /etc/iscsi/initiatorname.iscsi file, provided by the iscsi-initiator-utils package, contains the iSCSI initiator names.

Prerequisites

The targetcli service is installed and running.
An iSCSI target associated with a Target Portal Groups (TPG).

Procedure

Optional: To disable auto mapping of LUNs to ACLs see Creating a read-only iSCSI LUN.
Navigate to the acls directory:
```
/> iscsi/target_iqn_name/tpg_name/acls/
```

Use one of the following options to create an ACL:

Use the initiator_iqn_name from the /etc/iscsi/initiatorname.iscsi file on the initiator:

iscsi/target_iqn_name/tpg_name/acls> create initiator_iqn_name

Created Node ACL for initiator_iqn_name
Created mapped LUN 2.
Created mapped LUN 1.
Created mapped LUN 0.

Use a custom_name and update the initiator to match it:

iscsi/target_iqn_name/tpg_name/acls> create custom_name

Created Node ACL for custom_name
Created mapped LUN 2.
Created mapped LUN 1.
Created mapped LUN 0.

For information about updating the initiator name, see Creating an iSCSI intiator.

Verification

Verify the created ACL:

iscsi/target_iqn_name/tpg_name/acls> ls

o- acls .................................................[1 ACL]
    o- target_iqn_name ....[3 Mapped LUNs, auth]
        o- mapped_lun0 .............[lun0 ramdisk/ramdisk1 (rw)]
        o- mapped_lun1 .................[lun1 block/block1 (rw)]
        o- mapped_lun2 .................[lun2 fileio/file1 (rw)]

Additional resources

targetcli(8) man page

9.12. Setting up the Challenge-Handshake Authentication Protocol for the target

By using the Challenge-Handshake Authentication Protocol (CHAP), users can protect the target with a password. The initiator must be aware of this password to be able to connect to the target.

Prerequisites

Created iSCSI ACL. For more information, see Creating an iSCSI ACL.

Procedure

Set attribute authentication:

/iscsi/iqn.20...mple:444/tpg1> set attribute authentication=1

Parameter authentication is now '1'.

Set userid and password:

/tpg1> set auth userid=redhat
Parameter userid is now 'redhat'.

/iscsi/iqn.20...689dcbb3/tpg1> set auth password=redhat_passwd
Parameter password is now 'redhat_passwd'.

Additional resources

targetcli(8) man page

9.13. Removing an iSCSI object using targetcli tool

This procedure describes how to remove the iSCSI objects using the targetcli tool.

Procedure

Log off from the target:
```
# iscsiadm -m node -T iqn.2006-04.example:444 -u
```
For more information about how to log in to the target, see Creating an iSCSI initiator.
Remove the entire target, including all ACLs, LUNs, and portals:
```
/> iscsi/ delete iqn.2006-04.com.example:444
```
Replace iqn.2006-04.com.example:444 with the target_iqn_name.
- To remove an iSCSI backstore:
```
/> backstores/backstore-type/ delete block_backend
```
  - Replace backstore-type with either fileio, block, pscsi, or ramdisk.
  - Replace block_backend with the backstore-name you want to delete.
- To remove parts of an iSCSI target, such as an ACL:
```
/> /iscsi/iqn-name/tpg/acls/ delete iqn.2006-04.com.example:444
```

Verification

View the changes:
```
/> iscsi/ ls
```

Additional resources

targetcli(8) man page

Chapter 9. Configuring an iSCSI target

9.1. Installing targetcli

9.2. Creating an iSCSI target

9.3. iSCSI Backstore

9.4. Creating a fileio storage object

9.5. Creating a block storage object

9.6. Creating a pscsi storage object

9.7. Creating a Memory Copy RAM disk storage object

9.8. Creating an iSCSI portal

9.9. Creating an iSCSI LUN

9.10. Creating a read-only iSCSI LUN

9.11. Creating an iSCSI ACL

9.12. Setting up the Challenge-Handshake Authentication Protocol for the target

9.13. Removing an iSCSI object using targetcli tool

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