Mountedness test for shell scripts

pwabrahams · 05-08-2009, 11:51 AM

Is there a test that I can use in a shell script to test if a remote mount specified in /etc/fstab has been completed? Better yet, is there a test that will tell me if all mounts have been completed without referring to each of them explicitly?

I'm trying to construct a script that will keep retrying a mount until it is accomplished and then go away.

tredegar · 05-08-2009, 12:14 PM

You could test to see if a particular file on the mounted device is present at the mountpoint.
If it's there, the device is mounted. If it's not, it isn't (or someone has deleted the file).

-Or-

mount tells you what is mounted where, and how.

So you could grep the output of mount and test if a particular device is mounted:

Code:

foo=$(mount | grep mountpoint)
if [ "$foo" != "" ] ;  then
echo "Mounted"
else
echo "Not mounted yet"
fi

-Or-

This is linux, so there will be other, possibly more "elegant" ways.

pwabrahams · 05-08-2009, 12:30 PM

It would be nice if there was something I could put into /etc/rc.local that would keep retrying the mounts until they all succeeded but was independent of the particular contents of /etc/fstab. I suppose I could construct a program that examines /etc/fstab and, for each item mentioning cifs or nfs, tests if it is mounted. But that would be a fair amount of work and might be overkill.

I wish there was a form of the mount command that keeps trying the mount until it succeeds, but there doesn't seem to be, particularly for cifs.

i92guboj · 05-08-2009, 01:03 PM

Simple shell scripting will suffice:

Code:

while ! mount /dev/foo /mnt/foo; do sleep 6; done

The loop will only end when mount succeeds. Of course, change that mount command by your own one, and change the 6 seconds period for whatever you wish.

tredegar · 05-08-2009, 01:14 PM

Quote:

while ! mount /dev/foo /mnt/foo; do sleep 6; done

I like it

But have no use for it

But my thanks for an "elegant" solution!

i92guboj · 05-08-2009, 01:18 PM

Quote:

Originally Posted by tredegar

I like it

But have no use for it

But my thanks for an "elegant" solution!

Why?

Can't you just put it into any init file? If it locks the boot process just add & to launch it in the background.

pwabrahams · 05-08-2009, 04:46 PM

Quote:

Originally Posted by i92guboj

Simple shell scripting will suffice:

Code:

while ! mount /dev/foo /mnt/foo; do sleep 6; done

I think there's a problem with this if the mount has succeeded before the script gets executed. In that case you'll get a duplicate mount, which Linux seems to allow.

It also has to be customized for each nfs/cifs entry in fstab and modified whenever the set of remote mounts changes. It's easy to forget to do that when changing fstab. Perhaps an awk program should be used to scan fstab and extract a list of filenames.

Perhaps there just isn't a purely passive way of checking for mountedness.

i92guboj · 05-08-2009, 04:52 PM

The easiest way to see if something's been mounted is to check /etc/mtab.

That's just the basic example on how to do it, of course you can improve it for additional checks, automatic fstab lookup, etc. etc.

The smart way would be to write a service for your distribution that you can add to your runlevel, start or stop at your discretion.

pwabrahams · 05-08-2009, 10:56 PM

Quote:

Originally Posted by i92guboj

The easiest way to see if something's been mounted is to check /etc/mtab.

Not the easiest to automate, but the most reliable, I'd agree. I wish there was a variant of the mount command that would produce a condition code for mountedness, but there doesn't seem to be.