Read Only FS

[Tim Riker]

three main choices:

romfs, cramfs, jffs2

romfs is uncompressed and so does not need to decompress.

cramfs is compressed and indexed, and so has shorter boot time

jffs2 is compressed but must do a full scan on bootup. It can be
read/write.

Consider that flash reads may actually take longer than decompression
depending on your hardware. I'd recommend a single jffs2 partition for
most applications. This is the best use of a small amount of flash.
Mount it readonly most of the time if you like and have some way to
snapshot the current config data that remounts read-write, saves, and
then remounts read-only. I have often made /var ramfs with /tmp ->
/var/tmp, and /dev -> /var/dev so that writes can happen there. Then the
bootup script fully populate /var.

Jose Rodríguez Argente wrote:
> 
> Hello,
> 
>    I am working on an Assabet platform. My application will have a
> significant part of the root filesystem mounted as read-only. I am
> thinking about installing it as romfs, which I think should be faster
> than JFFS2. Am I right?
> 
> Another question is wether romfs runs over MTD or it has its own access
> layer.
> 
> Thank you very much
> 
> ______________________________________________________
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-- 
Tim Riker - http://rikers.org/ - short SIGs! <g>
All I need to know I could have learned in Kindergarten
... if I'd just been paying attention.