e2image, ext3 and nightly backups.
bothie at gmx.de
Sat Mar 6 01:33:58 UTC 2004
Daniel Pittman <daniel at rimspace.net> wrote:
> Is e2image worth running if the file system is online and in use, under
> the 2.6 series kernels, as part of a nightly backup run?
Yes IMHO (but on other kernel versions, too).
> If there /is/ a risk of the data being incomplete or incorrect,
There *is* (unless you can -o remount,ro before running e2image).
> is there
> anything that can be done to make this less likely or to detect the
1. e2image to a file called a
2. e2image to a file called b
3. Compare the files - if they are identical you are done - remove file b.
4. remove file a
5. rename file b to file a
6. go on at step 2
> Does e2image capture all the information necessary to support ext3 file
The only difference between ext2 and ext3 is the journal. It would be fatal
to replay that some days later from a backed up version. So it's senseless
at all to backup the journal.
> It looks to capture everything except the journal content; will this
> cause problems later if, say, the journal inode is destroyed but the
> content isn't? What if the journal inode /and/ content are destroyed?
See above. In general e2image is no replace for e2fsck. If the filesystem
gets really such horribly broken, that e2fsck cannot repair it, than the
data captured via e2image can be used to rescue the files. But as that will
make available only files which are some days old, you shouldn't bother
about the journal at all. Think about it this way: In general you will
never need the output of e2image at all. So if it is only a little bit
incomplete (missing journal or something similar) it's not worth worrying
about at all.
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