LiveCD wiping root partition?

[Michel Salim]

On 01/08/07, Douglas McClendon <dmc.fedora at filteredperception.org> wrote:
>
> Michel Salim wrote:
> > On 01/08/07, Douglas McClendon <dmc.fedora at filteredperception.org>
> wrote:
> >> Douglas McClendon wrote:
> >> Also, to answer your question more thoroughly than my first
> reply-  Yes,
> >> after
> >> the dd, if there is a seperate /usr or other partitions, files are then
> >> copied
> >> from / to there.  This is all very related to my turboLiveInst patch
> which
> >> I
> >> recently posted to livecd-list and anaconda-devel.
> >
> >
> > Uh. Does it ensure that the root partition is at least 4.0 GB in size,
> or
> > will it just try to dd the image regardless? I've had esoteric
> partitioning
> > in the past, with small /, and large /usr and /opt partitions.
>
>
> That it does.  Though the aforementioned turboLiveInst patch improves upon
> that,
> in that the rootfs only really needs to be 2.1G, which is the size of the
> uncompressed data that lives in the 4.0G filesystem image.  But as
> mentioned
> with that patch, that is still technically deficient for the case of
> separate
> /usr, where / needn't really even be 2.1G.  The solution to that is to
> have an
> alternate file level copy installation mechanism, rather than the (fast)
> block
> level fsimage copy installation mechanism.  This also fixes the potential
> problem of reintroducing support for non-ext3 (e.g. xfs) target root
> filesystems.
>
> >
> > I'm surprised I don't remember hearing about this bug before.  I had
> >> personally
> >> run into the same warning you saw, but that is just a general warning
> that
> >> has
> >> nothing to do with the livecd installer case specifically, and the
> livecd
> >> installer will stupidly let you just march along with the / fs not
> >> scheduled for
> >> formatting, even though it is going to anyway.
> >
> >
> > I guess we really need to have different types of updates, where major
> and
> > potentially data-loss-causing changes need to be more exhaustively
> tested.
> > No one probably bothered testing a live CD install to a non-formatted
> > partition before.
>
> F7 was the _first_ fedora release to have a livecd installer.  And that
> generic
> warning about choosing to not format '/', probably steered most people
> away from
> doing that.  But I agree, this situation should definitely be a part of
> some
> sort of test matrix.
>
> >
> > Still waiting for the dd process to finish backing up the partition to
> an
> > external drive; will report if anything is salvageable. Wishing I did
> not
> > blow away the Windows partition, would have made recovery much easier.
> >
> > While we're on the subject of making Anaconda changes, how about putting
> > /home on a separate partition? The BSDs traditionally do that, I think.
>
> No doubt you mean by default.  Personally I've long been a fan of the
> single
> large partition (to the extreme of going out of my way to put boot, swap
> and
> suspend2 areas on /).  Though these days, I tend to favor the 'upgrades
> are
> never worth it', and 'wipegrades are the future'.  So /home makes more
> sense for
> 'wipegrades'.  Although with all the version specific cruft that ends up
> in your
> homedir (~/.gnome*, blabla) I tend to have a subdirectory under home, and
> when I
> wipegrade, I only keep the subdir.  If I have any ~/.* files that are
> important
> enough, I keep a copy in the subdir, and a script to easily replace them
> after
> wipegrade (and gconftool2 to reintroduce all my desktop prefs).  Just my
> strategy, ymmv.


That's my strategy. Well, wipe the dots (apart from .gaim and a few others)
and keep Documents, Music, Pictures, etc. It gets a bit messy because there
are things in .gnome2 you definitely don't want to wipe too (epiphany puts
its bookmarks there if I'm not mistaken, and there's also Rhythmbox).
Writing a small script that chattr +i the important directories under the
hidden dirs and then wipe the remainders would do the trick in a more
systematic way, I suppose.

I guess the partition split does not even have to be / and /home, it just
has to be something that logically maps to RPM-managed vs non-RPM-managed.
So users that need persistent home directories (local users, basically)
should have home dirs in /local/home/ or something.

Anyway, hard lesson learned. I wonder how Ubuntu does their live CD install.
openSUSE is introducing one too, hopefully for their users the same bug does
not occur.

-- 
Michel
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