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From: Francis Moreau on 11 Mar 2010 04:56
Hello

I've the following (stupid) script that mount a device and umount it
right after the mount was succesfull:

--- 8< ---
#! /bin/sh

declare -i i=0
tmpdir=/tmp/foo.yYZ5szCyTv
node=/dev/sdc1

while :; do
mount -o ro,sync $node $tmpdir && {
umount $tmpdir || break
} || break
i+=1
echo $i
done
fuser $tmpdir
--- >8 ---

This fails during the first iteration with the following message from
umount(8):

umount: /tmp/foo.yYZ5szCyTv: device is busy.

but fuser(1) doesn't show anything.

So it looks like mount(8) initiates some operations which are not yet
finished when this process exits.

Could anybody shed some light ?

Are there any workarounds ? I found one which consists to add a
sleep(1) of one second between mount(8) and umount(8). But this looks
ugly.

Thanks
From: bort on 11 Mar 2010 09:46
I guess there are still filesystem initialization tasks or sth. going
on if you try to unmount so fast after mounting.
Try a sync(which will sync all disc caches :( ) before and/or use the
lazy unmount feature if you have it.

Take a look at
man mount
Option -l

-l
Lazy unmount. Detach the filesystem from the filesystem hierarchy
now, and cleanup all references to the filesystem as soon as it is not
busy anymore. (Requires kernel 2.4.11 or later.)


HTH
From: Francis Moreau on 11 Mar 2010 12:07
On Mar 11, 3:46 pm, bort <bernd.salo...(a)gmx.de> wrote:
> I guess there are still filesystem initialization tasks or sth. going
> on if you try to unmount so fast after mounting.

Yes, I think the same.

> Try a sync(which will sync all disc caches :( ) before and/or use the
> lazy unmount feature if you have it.

ouch that would be overkill, perharps I can find something else like

$ mount /dev/sdb1 /mnt && ls /mnt >/dev/null && umount /mnt

but I don't which command would be correct to use between mount and
umount

>
> Take a look at
> man mount
> Option -l
>
> -l
>     Lazy unmount. Detach the filesystem from the filesystem hierarchy
> now, and cleanup all references to the filesystem as soon as it is not
> busy anymore. (Requires kernel 2.4.11 or later.)

Well I would prefer mount(8) to be synchronous or umount(8) wait for
mount(8) to complete instead of failling.
From: mop2 on 11 Mar 2010 17:12
On Thu, 11 Mar 2010 06:56:40 -0300, Francis Moreau
<francis.moro(a)gmail.com> wrote:


>
> umount: /tmp/foo.yYZ5szCyTv: device is busy.
>
> but fuser(1) doesn't show anything.
>

I saw this some times, but using "lsof" the file in use
was always shown.
From: bort on 12 Mar 2010 08:28
How about

mount -rn <stuff>

to avoid writing /etc/mtab and mounting it read only?
Ever tried that?

Hope that helps :)
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