[buildd-tools-devel] Bug#679726: aufs

[Nicholas Bamber]

On 02/07/12 22:32, Nicholas Bamber wrote:
> On 02/07/12 22:12, Roger Leigh wrote:
>> On Mon, Jul 02, 2012 at 09:30:36PM +0100, Nicholas Bamber wrote:
>>> I have not got very far with aufs yet. Obviously I need to rtfm a bit
>>> more. However I have tried to follow the scroot scripts as best as I can
>>> and what I get is as follows:
>>
>> The only bit that matters is in 10mount (05union just creates
>> and removes the directories for the "overlay" and "underlay"):
>>
>> CHROOT_UNION_MOUNT_OPTIONS=br:${CHROOT_UNION_OVERLAY_DIRECTORY}:${CHROOT_UNION_UNDERLAY_DIRECTORY}=ro
>> mount -t "$CHROOT_UNION_TYPE" -o "$CHROOT_UNION_MOUNT_OPTIONS" "$CHROOT_NAME" "$1"
>>
>> So you just need to try doing
>>
>> mount -t aufs -o "br:${overlay}:${underlay}=ro" ${name} ${mountpoint}
>>
>> where
>>   overlay=overlay directory
>>   underlay=underlay directory
>>   name=any name you like
>>   mountpoint=where to mount
>>
>> If you can do that directly on the host system as root, then aufs
>> is working properly.  But if it's not, something is wrong, either
>> with the setup script, or with how schroot has been configured.
>>
>> Here's an example:
>>
>> % mkdir /tmp/a /tmp/b
>> % touch /tmp/a/1 /tmp/b/2
>> % ls /tmp/a /tmp/b
>> /tmp/a:
>> 1
>>
>> /tmp/b:
>> 2
>> % sudo mount -t aufs -o "br:/tmp/a:/tmp/b=ro" testaufs /mnt    
>> % mount | tail -n 1
>> testaufs on /mnt type aufs (rw,relatime,si=68977b847b3d0288)
>> ravenclaw% ls /mnt
>> 1  2
>> ravenclaw% touch /mnt/3
>> ravenclaw% ls /tmp/a /tmp/b
>> /tmp/a:
>> 1  3
>>
>> /tmp/b:
>> 2
>>
>> So you can see that /tmp/a is the writable overlay, so files
>> created in /mnt go into /tmp/a, and /tmp/b is the read-only
>> underlay.  If you can do the above, then aufs is working
>> correctly.  Note that I did a "modprobe aufs" beforehand,
>> but this should not be necessary.
>>
>> On the schroot side, you shouldn't need to do anything more
>> than set union-type=aufs.  Everything else should be automatic--
>> the chroot filesystem should be mounted/bind mounted/unpacked
>> on the underlay, and an empty directory should be the overlay.
>>
>>
>> Hope this helps,
>> Roger
>>
> 
> 
> nicholas at taylor:/home/sisyphus$ mkdir /tmp/a /tmp/b
> nicholas at taylor:/home/sisyphus$ touch /tmp/a/1 /tmp/b/2
> nicholas at taylor:/home/sisyphus$ ls /tmp/a /tmp/b
> /tmp/a:
> 1
> 
> /tmp/b:
> 2
> 
> 
> root at taylor:/mnt/share/childrens computer# mount -t aufs -o
> "br:/tmp/a:/tmp/b=ro" testaufs /mnt
> root at taylor:/mnt/share/childrens computer#
> 
> 
> nicholas at taylor:/home/sisyphus$  mount | tail -n 1
> testaufs on /mnt type aufs (rw,relatime,si=c13e1559eaba3ef4)
> nicholas at taylor:/home/sisyphus$ ls /mnt
> 1  2
> nicholas at taylor:/home/sisyphus$ touch /mnt/3
> nicholas at taylor:/home/sisyphus$ ls /tmp/a /tmp/b
> /tmp/a:
> 1  3
> 
> /tmp/b:
> 2


But:

root at taylor:/mnt/share/childrens computer# umount testaufs
/sbin/umount.aufs:plink.c:223: proc: No such file or directory
/sbin/umount.aufs:plink.c:223: proc: No such file or directory