[Xymon] Detecting read-only file system in Linux

[SebA]

Thanks Thomas. Simulating this suggests your code will work on our server,
but as you said, you are not 100% sure that the 'ro' will surface in the
mount command. The output here suggests that it may not:
http://sisyphus.ru/en/srpm/Sisyphus/xymon/sources/8
#!/bin/sh

# Read data from /proc/mounts on linux and report back in the xymon client
# It gives more accurate data than the 'mount' command and can catch
# disks in a read-only state.

test -r /proc/mounts && exec cat /proc/mounts
But maybe that is only needed for some other version of linux... Our server
is now fixed so I can't test it properly. But I do prefer a server-side
extension, or even a patch to xymon-server, to client plugins that I have to
install to every server. The issue with your code is that it only works for
1 named server ('bb.local'), so I would need to have something iterating
over all hosts. Probably not hard, and probably something that someone here
already does...
 
In fact, I think I have found the place to add it and that is in this
add-on: https://wiki.xymonton.org/doku.php/monitors:check-client - then it
will work for all hosts (correct me if I am wrong David Baldwin?)

Kind regards, 

SebA


  _____  

From: Xymon [mailto:xymon-bounces at xymon.com] On Behalf Of Thomas Eckert
Sent: 09 March 2015 14:05
To: Xymon MailingList
Subject: Re: [Xymon] Detecting read-only file system in Linux


Hi, 


On 09 Mar 2015, at 13:44, SebA <spah at syntec.co.uk> wrote:


(.)



Although we have some Debian systems, I was looking for a solution for
another Linux distro.
 
If I was to write something myself to do it, I would check /proc/mounts and
the best command I could find was:
awk '$4~/(^|,)ro($|,)/' /proc/mounts
which outputs:
/dev/root / ext3 ro,data=ordered 0 0
with sample line:
/dev/root / ext3 ro,data=ordered 0 0



You could use the reported "Client data" / "clientlog" with a server-side
extension. I have to admit that I'm not 100% sure if error-or-remounts are
reflected properly by this - but `mount` seems to use `/proc/self/mountinfo`
as it's datasource, so it _should_ be ok.

Extract the reported `mount`-data for host bb.local:

xymon 127.0.0.1 "clientlog bb.local section=mount"

Some testing of the output:

(export host=bb.local; xymon 127.0.0.1:1984 "clientlog $host section=mount"
| gawk '/[(,]+ro[,)]+/ { print "filesystem " $1 " mounted RO!" } ')

This would not require installing and maintaining an extension on every
client. One drawback would be increased latency as the ro-check would be
"indirect".

Cheers
Thomas

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.xymon.com/pipermail/xymon/attachments/20150309/e390ceb0/attachment.html>