Hi David, Thanks for the reply - see my comments below...
> -----Original Message----- > From: David Masover [mailto:[EMAIL PROTECTED] > Sent: 10 November 2006 16:54 > To: Roger Lucas > Cc: [email protected] > Subject: Re: reiserfsck with LVM read-only snapshot > > Roger Lucas wrote: > > > I have tried adding the "--no-journal-available" option to tell it *not* to > > replay the journal, > but it insists on trying to replay > > the journal, even though I have told it not to. When it does this, the > > same error occurs. > > Is there any way you can force reiserfsck to do this read-only? That's what I would like to know. I don't mind if I have to give reiserfsck somewhere else to write the rebuilt journal to (e.g. a file or similar), but I absolutely do not want it writing *back* to the snapshot. > > > I understand that Reiser3 is a journalling file system and you would > > normally replay the journal, > but I want to check my read-only > > copy of the snapshot so that I know it is valid. > > It isn't. > > By definition, assuming this is a snapshot of a live (mounted) > filesystem, it's not really valid -- it's as if you pulled the plug. I > can understand why you'd want to do this, but any way you run > reiserfsck, it's going to tell you that something's wrong, even if that > "something" is only that it hasn't replayed the journal yet. > I understand what you mean. I appreciate that snapshotting a live (i.e. mounted read-write) filesystem will give you just that, a snapshot, and individual files may be in a state of flux such that their contents are invalid or inconsistent. In this situation, however, the disk is mounted read-only so it *shouldn't* be changing. I'm just "snapshot"ing the read-only mounted image because I am paranoid. > > I don't want to change the snapshot in any way (e.g. such as writing the > > journal > > changes to it) so that I know the checksum and image data match. If I take > > a R/W snapshot then > run reiserfsck, it writes changes to > > the snapshot. > > I see where you're going with this. > > I don't use LVM for snapshots, but I do use dm_snapshot sometimes, for > exactly this sort of thing -- I have one device I don't want to touch, > so I grab a chunk of spare space (my swap partition) to use as a > snapshot device, and take a read/write snapshot and mess with that. My > original partition is untouched, but I can run fsck.reiser4 on the > snapshot, try to recover deleted files, etc. > > Now, bear with me. I know you want a read-only snapshot. > > What you want to do is create a read/write snapshot of your read-only > snapshot. That way, you can still have your checksum run on the > read-only snapshot, and it will match what you expect, but you can also > run reiserfsck on the read/write snapshot, and throw it away when you're > satisfied. Yep. That's what I would like too, but LVM cannot do snapshots-of-snapshots yet. > > I don't know the procedure for doing this with LVM, but I may be able to > show you how I'd do it directly with dm_snapshot. It's a bit more > cumbersome than if reiserfsck cooperated, but you're using a script > anyway, so it shouldn't be too bad. Hmmm. I'm not sure about dm_snapshot having not used it before and LVM seems to work pretty well (at least as far as its capabilities allow). I'm open to all suggestions, however. - Roger
