Re: mapping device name to iscsi target

[Todd Deshane <tmdeshan@vnet.ibm.com>]

Hi All, 

I have a working rule thanks to a response from Shawn Ferris. 

here it is: 

udev rule: 
BUS="scsi", PROGRAM="/lib/udev/iscsidev.sh %b", SYMLINK+="iscsi/%c/part%
n" 


iscsidev.sh script: 
------------------------------------------------------- 
#!/bin/sh 


# Sample Path: 
# /sys/class/scsi_host/host23/device/session19/iscsi_session:session19/targetname 


BUS=${1} 
HOST=${BUS%%:*} 


file="/sys/class/scsi_host/host 
${HOST}/device/session*/iscsi_session*/targetname" 


# This is not an open-scsi drive 
if [ -z "${file}" ]; then 
  exit 0 
fi 


target_name=$(cat ${file}) 


echo "${target_name}" 
--------------------------------------------------------- 


Notice that you could use the following line of code to dynamically 
detect the sysfs root (i.e. /sys), but with a read only 
environment /etc/mtab is disabled so I just hardcoded /sys as the sysfs 
root 
--------------------------------------------------------- 
SYSFS=$(mount -t sysfs | awk '{print $3}' 2>/dev/null) 
---------------------------------------------------------- 

Maybe this will help someone else in the future.

Todd 



On Sun, 2006-07-23 at 00:49 -0400, Todd Deshane wrote:
> Hi,
> 
> I know this topic has came up before on this list, but I still don't
> have a reliable solution.
> 
> It was suggested to use the persistent device naming which comes with
> udev:
> http://www.kernel.org/git/?p=linux/hotplug/udev.git;a=blob;f=etc/udev/60-persistent-storage.rules
> 
> (see:
> http://marc.theaimsgroup.com/?l=linux-hotplug-devel&m\x115036155509938&w=2
> for details)
> 
> since it gives the /dev/disk entries such as by-id,by-label and by-uuid,
> but i am not sure how to map the uuid back to the iscsi target.
> Has anyone done this successful or have any ideas?
> 
> Also, the idea of using the bus id %b seems like a good idea, (see this
> thread:
> http://marc.theaimsgroup.com/?l=linux-hotplug-devel&m\x106928672620090&w=2
> for details) but doesn't appear to be reliable enough: here is the code
> if have for it so far for it:
> 
> 
> I used the rule:
> BUS="scsi", PROGRAM="/lib/udev/iscsidev %b"   NAME="%c%n" SYMLINK="%k"
> 
> with the /lib/udev/iscsidev script as follows:
> #!/usr/bin/python
> import sys
> import os
> import re
> 
> arg = sys.argv[1]
> (targname,bus,targ,lun) = arg.split(':')
> for targets in os.popen('/sbin/iscsiadm -m session','r').readlines():
>     toMatch = re.compile('\[0*' + str(targname) + ':')
>     isMatch = toMatch.search(targets)
>     if(isMatch):
>         (head,addr,target_name) = targets.split();
> sys.stdout.write(target_name)
> 
> script is based off of the perl version in:
> http://groups.google.com/group/open-iscsi/browse_thread/thread/bc050f805c8f85c/fb0ff969e8da7629?q=udev&lnk=gst&rnum=2#fb0ff969e8da7629
> 
> In most cases this seems to work perfectly... it prints out the target
> name and there is a nice mapping (targetname to actual device). However,
> the problem seems to be that the bus id %b in the  udev rule above can
> get out of sync with targname in the script.
> 
> targname refers to the 'xx' in the output of the command iscsiadm -m
> session
> for example:
> # iscsiadm -m session
> [xx:<record id>] <host>:<port>,1 targetname
> 
> with a quick look at the source code the xx seems to refer to the
> session id, which is not necessarily the same as the bus id, hence the
> problem of out of sync.
> 
> So, what is the recommended way to get this mapping that
> is reliable?
> 
> Any experience with this? ideas/suggestions?
> 
> Thanks in advance,
> Todd
> 
> 
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