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Re: LiveCD wiping root partition?



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

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.
Pretty much every live cd does a dd afaik.
ubuntu 7.04 keeps their rootfs natively on squashfs (versus fedora which
keeps
it natively on an ext3 image which lives on a squashfs).

Therefore they can't be doing a dd for the install.


Any reason why dd is preferred over, say, tar? The latter would be much
safer. And files would not have to be moved to their final partitions after
'dd' too.

seeking (cdrom and disk). Lots slower (5X?). I suspect that file level copy (tar) will be the long term answer for the flexible general case. Though I also suspect the much faster dd will be part of the long term answer as well for the typical case (i.e. formatting / as ext3, and no separate /usr).

For example, on my system, using the existing 4.0G dd, the copy takes 299s. Using my turboLiveInst patch, I can shave that down to 250s. Using tar however to copy the 85896 files, took 1247s. And you also need to throw in another 30s or so for the format that isn't required in the dd case. Maybe(??) there is some more efficient way to copy those 85K files than the ( tar cpsf - | tar xpsf - ) that I used for that trial.

Lastly safety has nothing to do with the tar vs dd issue. The safety issue had to do with the bug of the user interface not accurately reflecting what was happening. fyi, I did go ahead and file the bug, and even submit a patch which might fix it.

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=250301

That doesn't mean of course that you don't have every right and justification to be cursing the bits of the F7 livecd while watching it spark in a microwave.

-dmc



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