aufs

Hello Michael,

"Dipl.-Ing. Michael Niederle":
> I check all files whether they are opened or not before removing them from the 
> ramdisk-layer. It seems that I must not remove any file within a directory if 
> only a single file within that directory is kept open - otherwise I end up with 
> an empty directory (seen by aufs - in the layers everything looks fine). This is 
> definitely *not* a problem with whiteout-files.)
> 
> I used the "udb=reval" and "udb=inotify" options - but without success. And 
> worse, sometimes I (logically) lose files even when I make all those checks.

Which is your case?

- /aufs = /rw_ram + /ro_ext2_img + /rr_squash
- cp /rw_ram/fileA /ro_ext2_img (bypassing aufs)
- rm /rw_ram/fileA (bypassing aufs)
- "ls /aufs" does NOT show fileA

or

- /aufs = /rw_ram + /ro_ext2_img + /rr_squash
- dir = opendir("/aufs")
- readdir(dir)
- cp /rw_ram/fileA /ro_ext2_img (bypassing aufs)
- rm /rw_ram/fileA (bypassing aufs)
- readdir(dir) does NOT show fileA

In the former case, I guess udba=inotify will solve the problem (you
should use the latest aufs which is updated this Monday).
In the latter, it is a generic feature/specification of unix
filesystem. You need to call rewinddir()


Junjiro Okajima

"Dipl.-Ing. Michael Niederle":
> I check all files whether they are opened or not before removing them from the 
> ramdisk-layer. It seems that I must not remove any file within a directory if 
> only a single file within that directory is kept open - otherwise I end up with 
> an empty directory (seen by aufs - in the layers everything looks fine). This is 
> definitely *not* a problem with whiteout-files.)

I have to warn you one thing.
You need to be careful about the pseudo-links unless you didn't specify
noplink mount option.
It is recommended to execute "auplink /your/aufs flush" before you clean
up the top writable branch.


Junjiro Okajima

On Wed January 23 2008 20:12, sfjro@... wrote:
> 
> "Dipl.-Ing. Michael Niederle":
> > I check all files whether they are opened or not before removing them from the 
> > ramdisk-layer. It seems that I must not remove any file within a directory if 
> > only a single file within that directory is kept open - otherwise I end up with 
> > an empty directory (seen by aufs - in the layers everything looks fine). This is 
> > definitely *not* a problem with whiteout-files.)
> 
> I have to warn you one thing.
> You need to be careful about the pseudo-links unless you didn't specify
> noplink mount option.
> It is recommended to execute "auplink /your/aufs flush" before you clean
> up the top writable branch.
>

Could you include a demonstration of the proper mount options and procedure
in the samples/auroot/{README,script} please?

Perhaps pretend that apache had a directory that accept uploads/puts - something
that had to be moved from the top rw to the lower ro from outside of the aufs view.

Mike

> 
> Junjiro Okajima
> 
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>

"Michael S. Zick":
> Could you include a demonstration of the proper mount options and procedure
> in the samples/auroot/{README,script} please?
> 
> Perhaps pretend that apache had a directory that accept uploads/puts - something
> that had to be moved from the top rw to the lower ro from outside of the aufs view.

I don't think it is related to the auroot script.
The auroot is a sample for replacing chroot(8).

I guess what you want is something like this,

- install mount.aufs auplink aulchown
- customize /etc/default/auplink
- mount -o remount,noplink,udba=inotify /your/aufs
- direct modifications to your branches
- mount -o remount,plink,udba=reval /your/aufs


Junjiro Okajima