ISCSI

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Target

targetcli-fb

All major Linux distributions switched to LIO now and should have the targetcli-fb package available.[1] 

apt-get install targetcli-fb                                                               # Debian, Ubuntu
dnf install targetcli                                                                      # Fedora
emerge sys-block/?                                                                         # Gentoo

The targetcli utility must can be used to create and configure our target in an interactive dialog.[2][3] Once configured, the actual configuration file is then saved to /etc/target (resp. /etc/rtslib-fb-target in Debian), which can be looked at, but shoud not be edited.

Let's create a simple target: 

/> cd backstores/fileio
/backstores/fileio> create disk0 /var/tmp/disk0.img
Created fileio disk0 with size 1073741824

/backstores/fileio> cd /iscsi
/iscsi> create iqn.2023-10.org.example:0                             # iSCSI Qualified Name according to RFC 3720
Created target iqn.2023-10.org.example:0.
Created TPG 1.
Global pref auto_add_default_portal=true
Created default portal listening on all IPs (0.0.0.0), port 3260.

Adjust the portal address if needed: 

/iscsi> cd iqn.2023-10.org.example:0/tpg1/portals/
/iscsi/iqn.20.../tpg1/portals> delete 0.0.0.0 3260 
Deleted network portal 0.0.0.0:3260

/iscsi/iqn.20.../tpg1/portals> create ip_address=127.0.0.1 ip_port=3260
Using default IP port 3260
Created network portal 127.0.0.1:3260.

Create a LUN: 

/iscsi/iqn.20...xample:0/tpg1> cd ../luns
/iscsi/iqn.20...e:0/tpg1/luns> create /backstores/fileio/disk0
Created LUN 0.

Create a default ACL, for the initiator from /etc/iscsi/initiatorname.iscsi: 

/iscsi/iqn.20...e:0/tpg1/luns> cd ../acls
/iscsi/iqn.20...e:0/tpg1/acls> create iqn.1994-05.com.redhat:8249dc99df3
Created Node ACL for iqn.1994-05.com.redhat:8249dc99df3
Created mapped LUN 0.

Exiting the configuration tool will save the configuration. Once an initiator is connected, we can see its session too: 

/> sessions
alias: fedora    sid: 1 type: Normal session-state: LOGGED_IN

Adding (and removing) new disks can be summarized as: 

/> /backstores/fileio/ create disk3 /var/tmp/disk3.img
/> /iscsi create iqn.2023-10.org.foobar:0

/> /iscsi/iqn.2023-10.org.foobar:0/tpg1/portals delete 0.0.0.0 3260                        # Only if needed!
/> /iscsi/iqn.2023-10.org.foobar:0/tpg1/portals create ip_address=127.0.0.1 ip_port=3260   # Only if needed!

/> /iscsi/iqn.2023-10.org.foobar:0/tpg1/luns create /backstores/fileio/disk3

/> /iscsi/iqn.2023-10.org.foobar:0/tpg1/acls create iqn.1994-05.com.suse:1234567

tgt

Contrary to targetcli-fb above, tgt can be used to set up an iSCSI target in user space. 

TBD

iscsi-target

NetBSD has iscsi-target that can be configured[4] as follows. 

TBD

Initiator

open-iscsi

The initiator has been implemented via the open-iscsi tools in Linux - install as needed: 

apt-get install open-iscsi                                                                 # Debian, Ubuntu
dnf install iscsi-initiator-utils                                                          # Fedora

Our own InitiatorName[5][6] can be obtained via: 

$ grep ^I /etc/iscsi/initiatorname.iscsi 
InitiatorName=iqn.1993-08.org.example:01:4997abfcc187

Or generated via: 

$ iscsi-iname -p iqn.$(date +%Y-%m).org.$(uname -n)
iqn.2023-10.org.example:ba54addae6a8

The syntax for iscsiadm is quite complicated, so let's show a few examples.

Discover existing targets via the portal interface: 

$ iscsiadm -m discovery -t sendtargets -p localhost
127.0.0.1:3260,1 iqn.2023-10.org.example:0

Once discovered, it will show up via discoverydb: 

$ iscsiadm -m discoverydb -o show
localhost:3260 via sendtargets

Login to the target discovered above: 

$ iscsiadm -m node -T iqn.2023-10.org.example:0 --login
Logging in to [iface: default, target: iqn.2023-10.org.example:0, portal: 127.0.0.1,3260] (multiple)
Login to      [iface: default, target: iqn.2023-10.org.example:0, portal: 127.0.0.1,3260] successful.

With that a new device should be present on our machine: 

lsblk --scsi
NAME HCTL       TYPE VENDOR   MODEL             REV TRAN
sdb  1:0:0:0    disk LIO-ORG  disk0            4.0  iscsi

$ dmesg -t | tail 
iscsi: registered transport (iser)
scsi host7: iSCSI Initiator over TCP/IP
scsi 7:0:0:0: Direct-Access     LIO-ORG  disk0         4.0  PQ: 0 ANSI: 5
sd 7:0:0:0: Attached scsi generic sg1 type 0
sd 7:0:0:0: [sda] 3906521088 512-byte logical blocks: (2.00 TB/1.82 TiB)
sd 7:0:0:0: [sda] Write Protect is off
sd 7:0:0:0: [sda] Mode Sense: 43 00 10 08
sd 7:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
sd 7:0:0:0: [sda] Optimal transfer size 2048 logical blocks > dev_max (256 logical blocks)
sd 7:0:0:0: [sda] Attached SCSI disk

List active session entries: 

$ iscsiadm -m session 
tcp: [3] 127.0.0.1:3260,1 iqn.2023-10.org.example:0 (non-flash)

Logout from a particular node: 

$ iscsiadm -m node -T iqn.2023-10.org.example:0 --logout
Logging out of session [sid: 3, target: iqn.2023-10.org.example:0, portal: 127.0.0.1,3260]
Logout of              [sid: 3, target: iqn.2023-10.org.example:0, portal: 127.0.0.1,3260] successful.

While the session has been logged out from, it can still be found in discoverydb: 

$ iscsiadm -m discoverydb
localhost:3260 via sendtargets

To remove this entry: 

iscsiadm -m discoverydb -t sendtargets -p localhost:3260 -o delete

iscsictl

NetBSD

On NetBSD the initiator can be configured via iscsictl.

Enable the initiator and start it: 

$ grep iscsi /etc/rc.conf
iscsid=YES

$ /etc/rc.d/iscsid start

Add a target: 

$ iscsictl add_send_target -a localhost:3260
Added Send Target 1

List targets: 

$ iscsictl refresh_targets
OK

$ iscsictl list_targets
    1: iqn.2023-10.org.example:0
       2: 127.0.0.1:3260,1

Login to the target: 

$ iscsictl login -P 1
iscsictl: login: The login failed

We haven't created an ACL on the target yet: 

kernel: iSCSI Initiator Node: iqn.1994-04.org.netbsd:iscsi.alice:0 is not authorized to access iSCSI target portal group: 1.
kernel: iSCSI Login negotiation failed.

Once the ACL has been configured, we can try again: 

$ iscsictl login -P 1
Created Session 3, Connection 1

$ dmesg
scsibus0 at iscsi0: 1 target, 16 luns per target
sd0 at scsibus0 target 0 lun 0: <LIO-ORG, disk0, 4.0> disk fixed
sd0: fabricating a geometry
sd0: 1024 MB, 1024 cyl, 64 head, 32 sec, 512 bytes/sect x 2097152 sectors
sd0: fabricating a geometry
sd0: async, 8-bit transfers, tagged queueing

List sessions: 

$ iscsictl list_sessions
Session 3: Target iqn.2023-10.org.example:0

And logout again: 

$ iscsictl logout -I 3
OK

$ iscsictl list_sessions
iscsictl: list_sessions: The list is empty

FreeBSD

FreeBSD carries iscsictl as well, albeit with a different syntax: 

iscsictl -A -p 10.0.0.3:3260 -t iqn.2023-10.org.example:0

Our own InitiatorName is still set to its default, but we can simplify our initiator setup with iscsi.conf: 

$ cat /etc/iscsi.conf
foobar {
       targetaddress   = 10.0.0.3;
       targetname      = "iqn.2023-10.org.example:0";
       initiatorname   = "iqn.2023-10.org.freebsd:0";
}

Login with: 

$ iscsictl -A -n foobar
$ iscsictl -L
Target name                          Target portal    State
iqn.2023-10.org.example:0            10.0.0.3         Connected: da0 da1 da2 da3

OpenBSD

TBD

iscsicpl.exe

Newer Windows versions can configure initiators via %systemroot%\System32\iscsicpl.exe.[7]

Links

References

  1. ↑ targetcli: Linux distributions
  2. ↑ LIO, Targetcli, and other tech videos
  3. ↑ How To Configure An iSCSI Target And Initiator In Linux
  4. ↑ HOWTO-iSCSI-target.txt
  5. ↑ Manually configuring an iSCSI device on a Linux system
  6. ↑ RFC 3721
  7. ↑ iSCSI Target Server overview
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