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Target Daemon (tgtd) - tgtadm

The target daemon is used to export storage targets to other hosts through the network.

To take control of the target daemon you have to use the tgtadm command line utility.

 

What you can do with tgtadm:

 

Show Targets

#: tgtadm --lld iscsi --op show --mode target

This command shows all current activated targets with their properties and active connections.

The output seems like the following:

Target 1: test1
System information:
Driver: iscsi
State: ready
I_T nexus information:
I_T nexus: 5
Initiator: iqn.1993-08.org.debian:01:8ced5dd1388
Connection: 0
IP Address: 192.168.2.219
LUN information:
LUN: 0
Type: controller
SCSI ID: deadbeaf1:0
SCSI SN: beaf10
Size: 0 MB
Online: Yes
Removable media: No
Backing store: No backing store
LUN: 1
Type: disk
SCSI ID: deadbeaf1:1
SCSI SN: beaf11
Size: 4295 MB
Online: Yes
Removable media: No
Backing store: /dev/vg0/testvm1
Account information:
ACL information:
192.168.2.219
  • In the first line you can get the target id (number) and the target name (here the id is 1 and the name is test1)
  • At the I_T nexus information part you can get an overview of currently connected hosts (here one host with the ip 192.168.2.219 is connected to this target)
  • The LUN 0 is the controller
  • At the LUN 1 part (should be 1 in every case) you can get information of the target like (the device which represents the target, if it is online, the size, ...)
  • At the lowest part of the output you can get the acl information. Only the hosts/networks which are represented here are allowed to discover and login to this target (here only the host with the ip 192.168.2.219 is allowed to do something with the target)

 

Create a new target

To create a new target the following 2 steps have to be performed:

 

Create an empty target

tgtadm --lld iscsi --op new --mode target --tid {tid} -T {target_name}
  • The tid is a numeric unique identifier for the target
  • The name is a freely choosable name for the target

 

Create a LUN for the target

tgtadm --lld iscsi --op new --mode logicalunit --tid {tid} --lun {lun} -b {block_device}
  • The tid is the identifier you have given at the creation process of the target
  • The lun number should be 1
  • The block_device parameter is the absolute path to device-file which is located in /dev

 

Before the target can be accessed by any host you have to add acl rules.

 

Access Control List - ACL

 

Set/Add a new ACL rule

tgtadm --lld iscsi --op bind --mode target --tid {tid} -I {ip_range}
  • tid is the identifier for the target you want to modify
  • ip_range can be one of the following:
    • a single ip (like "192.168.2.123")
    • a network (like "192.168.2.0/24")
    • "ALL" to deactivate address controlling

 


Delete a current existing ACL rule

tgtadm --lld iscsi --op unbind --mode=target --tid={tid} --initiator-address={ip_range}
  • tid is the identifier for the target you want to modify
  • ip_range can be one of the following:
    • a single ip (like "192.168.2.123")
    • a network (like "192.168.2.0/24")
    • "ALL" to deactivate address controlling

 

Delete a target

tgtadm --lld iscsi --op delete --mode target --tid {tid}
  • tid is the identifier of the target you want to delete

 

This removes the target from the active targets list. After running this command you can't see the target by running the show targets command.

 

Disconnect a client

tgtadm --op delete --mode conn --tid {tid} --sid {sid} --cid {cid}
  • tid is the identifier for the target on which you want to disconnet a client.
  • sid is the session id of the connected client. You can get this numerical identifier from the output of the show targets command. The number is at the end of the I_T nexus line. In the example at the top of the page the sid is 5.
  • cid is the connection id of the connected client.  You can get this numerical identifier from the output of the show targets command. The number is at the end of the "Connection" line. In the example at the top of the page the sid is 0.

 

Before disconnection a client you should delete the acl of the client you want to disconnect. If you don't do this the client starts reconnecting after the connection was broken. The result is a new connection from the client with new sid and cid.