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Re: LiveCD wiping root partition?



Douglas McClendon wrote:
Michel Salim wrote:
I just did a clean install of Fedora 7 from the live CD onto my laptop,
which previously had a Fedora install upgraded from one of the F7 test
releases, partitioned as suggested by anaconda (LVM, one swap partition,
everything else under '/')

When reinstalling, I kept the partition layout and specifically told
Anaconda *not* to reformat / (having booted in rescue mode beforehand, and
removing everything but /home). Anaconda gave a warning that the leftover
files might interfere with the installed system, which gave the impression
that those files won't actually be removed during installation.

I don't remember the specific warning, but if it is not clearly indicating that unselecting the format option on '/' is not allowed, then that is a bug that should be fixed either with better user messages, or alternate installation mechanisms.

WOW. I was wrong. There is NO such message. That is a horrible bug. I may try to check to see if it's still in the latest anaconda, and provide some sort of simple patch later today.

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.

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.

-dmc



I didn't have anything to do with what's in F7, though I did know enough about it to catch the fact that the 'formatting / filesystem' during the process was meaningless and time consuming, so that will be gone from from F8.


As it turns out, however, the old contents are completely gone (I'm trying out different recovery tools now to see if I could rescue some of the data). It's as if the live CD simply used dd to transfer the install image to the hard drive (in which case, how does it actually handle different partition layouts, e.g. /usr, /var, /home on separate partitions -- does it just move
the files afterwards?)

As it stands it seems that the Live CD is a very dangerous tool, at least as
long as
1) the default behaviour of Anaconda is to put everything under /
2) it does not carry more warnings about what it will do to the / partition
during installation

Could someone let us know how the live CD actually performs its work?


It takes a 4.0G ext3 fsimage from the cd, effectively dd's it to the chosen root volume, then does a resize2fs.


It
would aid tremendously in the data recovery part. Would 'dd'-ing the entire partition to an external drive, and mounting it on a Windows computer (most
recovery tools are unfortunately for that platform) preserve all the data
required? I'm assuming that the new installation overwrote the same parts of
the disk that was used to hold the OS in the previous install.

As long as you haven't done much, data that was sitting in the first 4.0G of the filesystem will be gone, but data in the rest should be largely untouched. I have no idea how to go about trying to recover it (haven't used any windows tools), except asking for expensive professional date recovery help. Or if all I cared about was a text file, using 'strings' and 'grep' on chunks of the disk data.

-dmc



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