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Re: LiveCD wiping root partition?





On 01/08/07, Douglas McClendon <dmc fedora filteredperception org> wrote:
Michel Salim wrote:
> On 01/08/07, Douglas McClendon <dmc fedora 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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