On 11/02/15 13:35, sf...@users.sourceforge.net wrote: > OmegaPhil: >> The crux of the problem is aufs returned success when unmounting, when >> it shouldn't have as not everything had released references to the >> volume. That was my question. > > Still I don't understand what you wrote. > It would be better if you write a simple script or C program > (in system-programming) to reproduce the problem on a generic system > other than yours. > > For example, > > - you have an entry in /etc/fstab, let's call the fs-type is sillyfs. > - your cgmanager is running as usual, and it holds the sillyfs mounted. > - you try unmounting the sillyfs in another namespace and FAILED. > > Assuming this behaviour is what you want, if you replace sillyfs by > aufs, you would succeed unmouting in the last step. And you think this > aufs behaviour is a problem, right? If so, I'd ask you to represent it > in a simple script. And does there such sillyfs exist in real world? > What is it? > > > J. R. Okajima
I'm not taking this further at the moment, I'm simply letting you know that currently aufs does not know when a volume genuinely unused, and therefore OK to unmount (the underlying problem of cgmanager breaking stuff is now easy to work around, but it exposes this more serious issue). I suspect this is due to bad handling of namespace stuff (that I know nothing about) on behalf of cgmanager, but even in such a case, when an unmount succeeds, that is taken by the user as a guarantee that nothing is hooked into the volume(s) managed by aufs, or any other filesystem. If anyone is interested, this is trivial to reproduce in Debian Testing currently (cgmanger v0.35-1 or below): 1. aufs volume maintained in fstab. 2. Ensure sysvinit is in place, not systemd: sudo aptitude install sysvinit-core 3. Start the system up into runlevel 2, unmount the aufs volume - this will succeed. 4. Try to move the old mountpoint - it will fail. 5. sudo /etc/init.d/cgmanager restart 6. You can move the mountpoint directory now. Thanks for your time earlier - I'll be active on the cgmanager bug.
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