On Wed, Jul 27, 2005 at 01:10:43PM +0200, Anonymous wrote: > I'm thinking of switching from ext3 back to ext2 because the wiping > utilities (shred, srm) aren't supposed to work on journaled > filesystems. But I'm also thinking of mounting ext2 synchronously to > reduce the risk of data loss (power cuts, etc).
I'm the author of wipe, btw (the one at wipe.sf.net). Meta-data journaling alone isn't a problem (except for wiping filenames), but full data journaling is, and some journaled fs (like reiser) don't necessarily place data on the same blocks when you overwrite (log-structured and versioning filesystems, especially). To be sure you overwrite the old blocks, you have to overwrite the whole partition. That's why it's best to encrypt sensitive data in the first place. That way, there's no plain text left around. > What will I screw up if I do this? I'd just stick to ext3. I believe (but i'm not certain) that ext3 currently writes the same file offset to the same blocks. That may not be the case in the future (eg, fs-level snapshots). > I notice that the BSD people normally use synchronous filesystems and > we GNU-Linux people normally use async. Why? Are they wrong or just > different, and how? There's a few reasons. Linux's e2fsck was good enough that most of the time, it could repair an async-mounted ext2 w/o much trouble. The problem though, is async breaks things like mail, which rely on rename being synchronis (which is another discussion). For a long time (maybe still) mounting ext2 sync wasn't as strict as bsd sync-mounts (i believe ext2 was at least improved, in the last year - i remember a patch being posting on the l-k list). The main reason linux defaulted to async for ext2, was speed. BSD was more concerned with correctness and reliability for things such as mail and news serving. Journing with data=ordered provides the same safety as sync-mounts, but better performance and no lengthy fsck. BSD softdeps also provides better performance (and the same guarantees) as sync, but still requires fsck if not cleaning umounted. > Alternatively, can anyone recommend a file-wiping tool that > purges/wipes the ext3 journal as well as overwriting the file? wipe -Tx1 /dev/... ;) If you do use my util, get the latest WIP version from sourceforge. There's a couple minor bug fixes. -- Tom Vier <[EMAIL PROTECTED]> DSA Key ID 0x15741ECE -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
