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Re: Changing root journal data mode

On Sep 05, 2001  20:08 -0700, Mike Fedyk wrote:
> On Wed, Sep 05, 2001 at 07:38:29PM -0600, Curtis Hogg wrote:
> > > Could you also just use tune2fs to change the journal type? I haven't
> >>  looked much at the docs for it but perhaps you could, since you use that
> > > to actually make your fs ext3...
> >From what Andreas Dilger said, it looks like that information is not in the
> >super block at this time.

Correct, the journaling mode is currently only selectable as a mount option.
However, it _would_ be tune2fs that is responsible for changing this when/if
such a feature is available.

> Also if IIRC, tune2fs is only safe with the -j and -J options while mounted
> because it just creates a file, and doesn't modify the super blocks.  All
> other (still true?) options for tune2fs have to be used on an unmounted FS.

No, in recent versions of e2fsprogs, it is possible to change most fields
in the superblock via tune2fs on a mounted filesystem.  This doesn't
necessarily mean that these settings will be effective immediately.  For
example, it is possible create a journal on a mounted fs (setting the
"HAS_JOURNAL" flag in the superblock, and creating a journal file)
but this won't turn a mounted ext2 filesystem into ext3 until it is
unmounted and mounted again.  Many of the superblock fields are only
checked at mount time.

Cheers, Andreas
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

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