wd at denx.de
Fri Aug 27 17:38:33 EST 2004
In message <20040827013550.73877.qmail at web15605.mail.cnb.yahoo.com> you wrote:
> > Are you really surprised that opening a file for
> > writing fails on a read-only filesystem???
> So only for this reason, I cannot choose Cramfs for my
> application deployment??? Then I have nearly no other
Why not? Of course you can. You just cannot write to it.
> choice but use JFFS2 for deployment, which performance
> couldn't compare with RAMDISK.It's a pity that RAMDISK
> cannot update some info permanently. EXT2 seems not a
You can use any filesystem, including one on a RAMDISK.
If the root filesystem happens to be read-only, you just need to
provide a writable filesystem for those things that need to get
written. In case of data that may get lost at reboot you can use
tmpfs, and for persistent storage you can use JFFS2.
If you are concerned about updating individual files in your
read-only filesystem (instead of updating the whole image (*)) you
can use an overlay filesystem. For example, you can use "mini_fo"
which was specifically tailored for such purposes; please see
(*) Updating the whole image is not a bad idea - this way you can
guarantee that all files int he image are really compatible with
each other; keeping the system in a consisten state is much more
difficult when individual files can get replaced at random.
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de
"UNIX was not designed to stop you from doing stupid things, because
that would also stop you from doing clever things." - Doug Gwyn
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