What is /.journal?

[Rick Stevens]

On Tue, 2005-12-27 at 20:04 +0300, A.Fadyushin at it-centre.ru wrote:
> The /.journal file is created when the _existing_ EXT2 filesystem is
> converted to EXT3 filesystem. That file contains the filesystem journal
> used by EXT3. The file is only created during the conversion EXT2->EXT3
> because it is impossible to create separate region on the existing EXT2
> filesystem for the journal - therefore, the journal is placed in the
> file /.journal (which is similar to regular files but is unremovable
> under EXT3). When the EXT3 filesystem is created anew, the journal is
> placed on disk separately from the space used for files' data, so there
> is no need to reserve that space via special file entry.

Perfect answer, Alexey.  That is correct.  If you convert an ext2 to
an ext3 filesystem, the system must put the journal somewhere, so it
creates a ".journal" file in the root of the filesystem and puts the
journal there.  A freshly created ext3 filesystem reserves space OUTSIDE
the namespace for the journal, hence it doesn't show up in a directory
listing.

It is important that you NOT delete the ".journal" file (permissions are
set so it's difficult to do anyway), because if you do, you will cease
to have an ext3 filesystem and you may even have issues mounting it
since the ext3 module wants a journal and won't be able to find it.

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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
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-    If Windows isn't a virus, then it sure as hell is a carrier!    -
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