This page summarises configuring iSCSI on Debian 6 and 7. Thanks to HowtoForge's excellent "Using iSCSI On Debian Squeeze (Initiator And Target)" from which most of the information was learned.
iSCSI allows a server to provide a virtual block device over a network to a client. The virtual block device can then be treated like a real block device – for example it can be partitioned and file systems created in the partitions.
In iSCSI terminology the server is a "target" and the client is an "initiator". On this page they are called server/target and client/initiator.
HowtoForge's "Using iSCSI On Debian Squeeze (Initiator And Target)": http://www.howtoforge.com/using-iscsi-on-debian-squeeze-initiator-and-target
Open-iSCSI: http://www.open-iscsi.org/ including a README: http://www.open-iscsi.org/docs/README
iSCSI Enterprise Target: http://iscsitarget.sourceforge.net/
You will need:
aptitude -y install iscsitarget iscsitarget-dkms
Optionally backup the configuration files that will be changed: /etc/default/iscsitarget and /etc/iet/ietd.conf.
sed -i 's/ISCSITARGET_ENABLE=false/ISCSITARGET_ENABLE=true/' /etc/default/iscsitarget
The next step sets up to serve a single LVM volume, /dev/vg0/lv0. Values that need to be changed are red. The user and password values are need when configuring the client/initiator. Values that are arbitrary strings (so could be changed) are in blue.
user=someone
password=secret
local_device=/dev/vg0/lv0
oIFS=$IFS; array=($(hostname --long)); IFS=$oIFS
for ((i=${#array[*]};i>0;i--)); do backwards_fqdn+=.${array[i-1]}; done
( echo "Target iqn.$(date +%Y-%m)$backwards_fqdn:storage.lun0"
echo " IncomingUser $user $password"
echo " OutgoingUser"
echo " Lun 0 Path=$local_device,Type=fileio"
echo " Alias LUN0"
) > /etc/iet/ietd.conf
It can be useful to know the Target value just created when configuring the client/initiator. It can be displayed with
head -1 /etc/iet/ietd.conf
Further devices can be added by editing /etc/iet/ietd.conf, replicating and modifying the first stanza.
aptitude -y install open-iscsi
Optionally backup the configuration file that will be changed: /etc/iscsi/iscsid.conf.
sed -i 's/node.startup = manual/node.startup = automatic/' /etc/iscsi/iscsid.conf
In the next step, the iSCSI daemon is used to generate an initial configuration. Values that need to be changed are red. Starting the daemon will generate error messages because there's no configuration yet.
target_ip=192.168.10.27
/etc/init.d/open-iscsi restart
iscsiadm -m discovery -t st -p $target_ip
This should create a sub-directory of /etc/iscsi/nodes/ with the same name as the Target created when configuring the server/target.
Within that sub-directory there should be a further sub-directory with name beginning with the server/target's IP address.
Note: if the server/target has two IP address (accessible by the client/initiator?) there will be two such sub-sub-directories. It may be possible to configure a client/initiator to work this way but initial explorations did not identify how to do so. In this case, delete the sub-sub-directory for the IP address you do not want to use.
In the next step, the user name and password are added to the configuration.
Change to the new /etc/iscsi/nodes/<target>/<IP address ...> directory. In the commands below, the sed command should be on a single line.
user=someone
password=secret
sed -i "s/^node.session.auth.authmethod = None$/node.session.auth.authmethod = CHAP\nnode.session.auth.username = $user\nnode.session.auth.password = $password/" default
/etc/init.d/open-iscsi restart
The output should include:
Login to [iface: default, target: <target>, portal: <ip address>,<port>]: successful
and a new /dev/sd[a-z]+ device file should have appeared.
The new /dev/sd[a-z]+ block device can be configured as desired.
If it is configured with file system(s) to be mounted at boot there are special considerations for /etc/fstab:
If fscking is required ... TODO
The easiest way is to list /dev/disk/by-path/
If lshw is installed, more information is available by
lshw -class disk -class storage
hdparm doesn't work.
When smartctl was tried there was a kernel iSCSI target abort task on the target/initiator.