Networker

[Networker] NetWorker oddity - is it me or just the way it works?

2008-10-08 10:35:07
Subject: [Networker] NetWorker oddity - is it me or just the way it works?
From: George Sinclair <George.Sinclair AT NOAA DOT GOV>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Wed, 8 Oct 2008 10:32:13 -0400
This isn't really a question but more of an observation, really. I guess I'd just like to hear what others have to say on this matter. I'm not suggesting that this is news to anyone, but I really hadn't ever thought about this before until I did some testing recently. I think this is present in all NW versions, and it's simply the nature of the beast, good or bad. No biggie, really, just want to make sure that I'm not misunderstanding something.

OBSERVATION
By default, when NetWorker runs incrementals, it will back up any file whose file status time has changed or is newer than the last time incrementals ran. I know that that behavior can be changed to only use mod time, via directives, but otherwise, it's file status time. And file status time obviously includes more than just mod time changes like you would expect when a file is modified or newly created. So, for example, changes to the permissions, ownership, group, etc. would also force a file status time change (ls -lc), even if reset to the same value. A more subtle change, however, would be when moving a file from one location to another, which also resets the file status time and thus would force a backup. BUT, let's suppose someone renames a directory. In this case, the directory's file status time (ls -lc) would change, BUT the constituent files would still retain their previous times (not just mod times, but file status times also). As a result, if an incremental was run, only the pathname to the directory would be backed up and not the files. I've tested this, and that's the case. Only a full, numeric or running a manual incremental from the client, and specifying an older date, will force those files to get backed up, unless of course you affect a file status time change on them, e.g. 'chmod -R u+r dirname'. So NW just sees the times and rather than noticing that the files are now in different locations (different paths), it just ignores them since they're not newer than the previous incremental.

PROBLEM
This seems like a potential gotcha because if a user renames a directory, and then deletes the data, say a week later, and then you go to recover the directory from that incremental then all you'd recover would be the directory name. You'd have to go back further to get the files, but how would you know where to find them since they were last backed up under a different directory name??? Obviously, you could loop through all the save sets (say over the last month) for the parent file system using 'nsrinfo -s server -t nsavetime client' and grep for one of the file names to determine which directory contained it, or you could just browse around one day at a time, or some such thing, but it sounds like the only real answer to this is to expect the user to provide more info to clue you in as to the fact that the data had previously lived under another directory?

Does this make any sense? Any comments?

Thanks.

George



--
George Sinclair
NOAA/NESDIS/National Oceanographic Data Center
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