help: fail to create file in aufs

[Patrick Asselman]

On 2013-01-09 09:55, Haipeng Wu wrote:
> hi, 
>
> I have met a problem in creating file in aufs, below is the method to 
> reproduce:
> ----------------------------------------------
>
>  mkdir /tmp/aufs
> mkdir /tmp/aufs/temp
>  mkdir /tmp/aufs/mnt
>
>  sudo mkdir -p /tmp/aufs/root/abc
> sudo chmod 700 /tmp/aufs/root/abc     ### here must be 700
>
> sudo mount -t aufs -o br:/tmp/aufs/temp=rw:/tmp/aufs/root=ro+wh none
> /tmp/aufs/mnt
>  sudo chmod 777 /tmp/aufs/mnt/abc
>
> touch /tmp/aufs/mnt/abc/a   ### failed, permission denied, that's the
> problem I met
>
> ----------------------------------------------
>
> I have met the problem on both ubuntu 10.04 and 12.04.
> Any suggestions for this issue?
>
> thanks,
> haipeng

I have no knowledge whatsoever on aufs, so I may be completely wrong, 
but it seems to me that you are mounting /tmp/aufs/root with option 
read-only, so any changes you try to do on that mounted file system will 
of course get you the permission denied error.

Best regards,
Patrick Asselman