Stephan Schöffel wrote:
hi there,
i'm still new to unionfs. i followed the tutorial on this website
http://flaviostechnotalk.com/wordpress/index.php/2005/06/28/filesystem-snapshots-with-unionfs/
which was linked at the unionfs website.
the example did work but it does not fit my problem properly. i tries
different things but could not get it to work the way i want.
here is what i want:
i want (via script and using unionfs) to bring different directories
to their original state if the machine is rebooted. eg i want to
delete files users write to /tmp
i used the following approach:
modprobe unionfs
mkdir /tmp_union
mount -t unionfs -o dirs=/tmp=rw unionfs /tmp_union
mkdir /tmp_snap
unionctl /tmp_union --add --mode rw /tmp_snap
unionctl --mode ro /tmp
unfortunately, users can still write to /tmp and the changes are not
logged in /tmp_snap. is there a way to bring /tmp back to its original
state by using unionfs?
I'm going out on limb, but what you want depends on other things:
1. do you use a disk based filesystem for /tmp?
2. do you need large amount of space for /tmp?
One reason for these questions is that you COULD use a ramfs for /tmp.
On every
reboot, ram is cleared.
Aternative to ramfs or unionfs:
If a resident disk based filesystem is required, then just mkfs that
filesystem
before mounting it. An /etc/rc script with something like:
mkfs /dev/hda6
mount /dev/hda6 /tmp
Even if you do want to use a unionfs, you will have to mount that union
on /tmp
to prevent users from accessing the underlying filesystem:
1. mount the scratch filesystem somewhere users cant directly get to it,
such as
/var/scratch/tmp_snap
and make /var/scratch only accessable to root.
2. The readonly FS underlying scratch must be mounted somewhere users
can't get to
either:
/var/scratch/tmp
3. Mount the unionfs thus:
mount -t unionfs -o
dirs=/var/scratch/tmp_snap=rw:/var/scratch/tmp=ro none /tmp
4. and on every boot you still have to erase the tmp_snap.
Personally, I think you need either the ramfs or the non-unionfs version.
--stephan
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_______________________________________________
unionfs mailing list: http://unionfs.filesystems.org/
unionfs@mail.fsl.cs.sunysb.edu
http://www.fsl.cs.sunysb.edu/mailman/listinfo/unionfs
