Ubuntu 9.04 with file issues Cross posted by intent- we're supposed to compare notes on such problems - I hope.

[Jack]

You would have to go to the linux-ext4 mailing list archive and do a search.
I'm only stating from notes (copy and pastes w/ source notation, actually) I made of the conversations.

As far as 1 and 2 goes, this should be documented in many places (google). Some filesystem errors can mask other issues and new problems may appear after running a first pass fsck. Generally you want to re-run fsck until it reports no errors.
Here's a reference that explinas it quite succintly (look for "was modified"):
http://support.apple.com/kb/ts1417

As far as point 3 goes. that should be obvious and easily verified either: with any Linux reference that speaks of hardlinks, or creating a file and making hardlinks to it and testing. When a file is hardlinked, the system keeps track of the number of references to it, once the counter reaches zero the file is released. A hard link creates links, but retains one file. You can delete the original file and the links are still good. A softlink keeps one file and makes links, but if you delete the original file the link points to nothing. So if you have a problem with a multiply hardlinked file where the count is 1 and should be 2 and fsck -y deletes one of the references, the count goes to zero and poof, the file is gone.

Item 4 is more obscure, and I found it out from the ext4 mailing list. THe other information is findable there also.

Furthermore, if you run fsck on a mounted file system, you must cleanly reboot to ensure the changes made take effect. This is widely documented (one source: Running Linux, O'Reilly Books).

Lastly, if fsck fails because it can't mount it to check (ie the main superblock is corrupted) and you're using an ext2/3/4 filesystem. You can run fsck.extN -f -b <offset> <device> where offset is a multiple of 8192 plus 1 or whatever size you're using for blocking, and N is 2, 3, or 4. 8192 is, or was, the default block size. The -f is required, because the superblock copy may appear "clean". Every block has a copy of the superblock on ext2 and later filesystems.

Jack


--- On Sun, 9/5/10, Matthew Copple <mcopple at kcopensource.org> wrote:

> From: Matthew Copple <mcopple at kcopensource.org>
> Subject: Re: Ubuntu 9.04 with file issues Cross posted by intent- we're supposed to compare notes on such problems - I hope.
> To: kclug at kclug.org
> Date: Sunday, September 5, 2010, 11:06 AM
> Would you mind posting references to
> the conversations? A lot of this
> is new information to me, and I've been running ext* file
> systems for
> years. Most of the documentation I've found is pretty old.
> 
> Matt
>