[kwlug-disc] Backup and Recovery in the 21st Century

[Chris Irwin]

On Tue, Jan 12, 2010 at 13:19, Khalid Baheyeldin <kb at 2bits.com> wrote:

> Re: ext4.
>
> The print server I had was a clean Kubuntu 9.10 install, and defaulted
> to ext4. So I tried installing dump from the repository and it did install
> successfully.
>
> I ran dump on the / partition and it seemed to work. I used restore to
> list the contents of the dump and it did list the files in it.
>
> So, are you sure that ext4 does NOT support dump?


Great, you made me put my money where my mouth was and I lost. :)

I was making an assumption based on the man page (which still says ext2/3)
and google searches that corroborated it. In retrospect, I suppose nobody
posts to mailing lists saying "EVERYTHING IS OKAY", so if you're doing a
search to find problems, you'll only find problems. I should have, you know,
checked the actual documentation and changelogs.

I did an `apt-get source dump` on Ubuntu Karmic, and it seems that dump
0.4b42-1 has the following entry in the debian/changelog:
    * new upstream version, closes: #378349, #511651

The former refers to a documentation issue (not the ext4 omission), but the
later[1] refers to ext4. It seems dump was silently "working" but dumping
unrecoverable garbage from ext4, which is obviously bad (it should succeed
or fail, not both).

    [1] http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=511651

Since this appears to be solved, I decided to see what the upstream CHANGES
file had to say. Between b41 and b42 is the following entry:
    * Add (preliminary) ext4 support - thanks to libext2fs which does all
the job for us. Thanks to Gertjan van Wingerde for the patch.

So it looks like there is at least some support for ext4. It also seems that
since b40 Extended Attributes and ACLs are supported. I also noticed that
this update for ext4 support came out 18 June 2009, while the previous
release was over three years earlier on 2 January 2006. I'm not sure if that
is a feature or a deterrent when it comes to backup software :)

Since I am using LVM, I think snapshots + dump is going to prove quite
effective.

-- 
Chris Irwin
<chris at chrisirwin.ca>
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