mapping device name to iscsi target

mapping device name to iscsi target

[Todd Deshane]

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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Re: mapping device name to iscsi target

[Todd Deshane]

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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> Join SourceForge.net's Techsay panel and you'll get the chance to share your
> opinions on IT & business topics through brief surveys -- and earn cash
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