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Many problems with live-rw partition



Il gioved? 21 agosto 2008 21:12:25 Andreas Bombe ha scritto:

> > > It is used in the aufs after all, so it doesn't work.  My fix for that
> > > one was not triggering the remount ro attempt by commenting the
> > > try_snap calls in scripts/live since I do not need snapshot files here.
> >
> > I need to think on how to handle that case.
>
> I haven't yet followed the flow in the live scripts, but my idea would
> be to note the existence of live-rw without immediately using it.  Make
> it part of the root union only at the end.

I was imaging the opposite, taking note of used live-rw in scanning for other 
types of persistences or snapshots, but your idea is good, although for 
snapshot types the live-rw should be already mounted before copying data for 
sure.

> > > Once I get it to boot without intervention, other issues crop up.  For
> > > one, /dev is in /live/cow and therefore saved unnecessarily.  Also,
> > > /etc/hosts and /etc/fstab appear to be appended with initial
> > > configuration unconditionally, meaning that they grow longer with every
> > > boot.  In the case of fstab it leads to tmpfs being mounted on /tmp
> > > multiple times.
> >
> > That is true, both exclude pattern and avoid unnecessaries appends needs
> > to be applied.
>
> This too might be fixed with a late mount of live-rw.  First a tmpfs
> would be made part of the root union for writability, all the
> initialization happens (and is thus not persistent) and finally live-rw
> is added.  The tmpfs would stay in the middle between live-rw and the
> read only image.

This is another great idea, anyone could imagine why this could lead to 
problems? In fact doing that only changes AFTER the live-initramfs job will be 
reminded and made persistent. I must think about that some more time.

> It would have the benefit of avoiding error prone special casing.
> However, I haven't examined the scripts enough to see if this is
> feasible.

A test suite is in the TODO list from a long time, a way to test a lot of use 
cases (network, usb, cd boots in presence of different persistent/snapshot 
modes from different types of filesytems...) in batch mode would be great to 
have.

-- 
ESC:wq



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