[ale] mounting backups

[Chris Fowler]

cramfs is good for backups and as a compressed fs for embedded stuff.

But:
Usage Notes
-----------

File sizes are limited to less than 16MB.

Maximum filesystem size is a little over 256MB.  (The last file on the
filesystem is allowed to extend past 256MB.)

Only the low 8 bits of gid are stored.  The current version of
mkcramfs simply truncates to 8 bits, which is a potential security
issue.

Hard links are supported, but hard linked files
will still have a link count of 1 in the cramfs image.

Cramfs directories have no `.' or `..' entries.  Directories (like
every other file on cramfs) always have a link count of 1.  (There's
no need to use -noleaf in `find', btw.)

No timestamps are stored in a cramfs, so these default to the epoch
(1970 GMT).  Recently-accessed files may have updated timestamps, but
the update lasts only as long as the inode is cached in memory, after
which the timestamp reverts to 1970, i.e. moves backwards in time.

Currently, cramfs must be written and read with architectures of the
same endianness, and can be read only by kernels with PAGE_CACHE_SIZE
== 4096.  At least the latter of these is a bug, but it hasn't been
decided what the best fix is.  For the moment if you have larger pages
you can just change the #define in mkcramfs.c, so long as you don't
mind the filesystem becoming unreadable to future kernels.


On Sat, 2004-01-10 at 22:14, Stephen Turner wrote:
> >  One thing you might try is google on cramfs and see what its
> > status is.
> 
> 
> yea thats about the only semi productive thing i found while googleing and
> its read only as well! but maybe with a little modification it can become
> write too, i dunno, havent ever done development stuff, altho it would be
> nice with some floppies using that :-p
> 
> =====
> ::: common sense? does it come with a manual?:::
> 
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