I've set up an experiment to test iscsitarget and initiator, which at some point worked. Later, I turned the setup back on and much to my dismay, the initiator machine stopped making block devices for its successful logins. As far as I know, I haven't changed anything on either machine.

Some details:

# iscsiadm -m node --login
Logging in to [iface: default, target: iqn.2010-12.nl.ytec.arbiter:arbiter.lun1, portal: 10.0.0.1,3260]
Logging in to [iface: default, target: iqn.2010-12.nl.ytec.arbiter:arbiter.lun2, portal: 10.0.0.1,3260]
Login to [iface: default, target: iqn.2010-12.nl.ytec.arbiter:arbiter.lun1, portal: 10.0.0.1,3260]: successful
Login to [iface: default, target: iqn.2010-12.nl.ytec.arbiter:arbiter.lun2, portal: 10.0.0.1,3260]: successful

Sessions:

# iscsiadm -m session
tcp: [3] 10.0.0.1:3260,1 iqn.2010-12.nl.ytec.arbiter:arbiter.lun1
tcp: [4] 10.0.0.1:3260,1 iqn.2010-12.nl.ytec.arbiter:arbiter.lun2

Netstat:

# netstat -n -p|grep 3260
tcp        0      0 10.0.0.2:48719          10.0.0.1:3260           ESTABLISHED 1078/iscsid     
tcp        0      0 10.0.0.2:48718          10.0.0.1:3260           ESTABLISHED 1078/iscsid

/var/log/syslog doesn't give errors:

Jan 27 11:41:49 vmnode001 kernel: [  378.041749] scsi7 : iSCSI Initiator over TCP/IP
Jan 27 11:41:49 vmnode001 kernel: [  378.044180] scsi8 : iSCSI Initiator over TCP/IP

lsscsi doesn't show my devices:

[0:0:1:0]    cd/dvd  TSSTcorp DVD-ROM TS-L333A D100  /dev/sr0
[4:0:0:0]    disk    ATA      Hitachi HUA72105 A74A  -       
[4:0:1:0]    disk    ATA      Hitachi HUA72105 A74A  -       
[4:1:0:0]    disk    Dell     VIRTUAL DISK     1028  /dev/sda

And there are no block devices in /dev for it:

# ls -1 /dev/sd*
/dev/sda
/dev/sda1
/dev/sda2
/dev/sda3
/dev/sda4

I tried loading all scsi kernel modules I could find, but that doesn't seem to be the problem.

I reall don't get this; it used to work. I found people with similar problems (here and here) but no solution.

Initiator is Debian Sqeeuze (testing), target is Debian Lenny (stable). iscsitarget is 0.4.16+svn162-3.1+lenny1, open-iscsi (initiator) is 2.0.871.3-2squeeze1. Target kernel: 2.6.26-2-amd64, initiator kernel: 2.6.32-5-amd64