On Wed, 20 Jan 2010, Johnny Hung wrote:
i'd also recommend you to consider if you really need the
ramdisk. when using a ram disk its entire content is loaded to the RAM
occupying space, even if you don't use certain files (or part of
them). other filesystems are more efficient in this aspect.
if the main purpose is to have a read only rootfs, i'd suggest a look
at squashfs.
I consider to use ramdisk as rootfs because worry about wrong
operation in rootfs (is use jffs2 rootfs) and it will cause system
boot up failed.
You have a point, however, you could do two things to help:
a) Mount the root file system as read-only. That way you can never write
to it, unless you remount it read-write. But you can still reflash that
partition if you need to upgrade.
b) Register the mtd partition holding the root file system as read-only.
This is even more seecure as remounting the file system won't permit
writes. However, it also means you can't write to it for upgrading. (I
don't think the mtd core permits changing an already registered mtd
partition from readonly to writable, but I could be wrong.)
Another query, does the syslogd/klogd log files also store in jffs2
rootfs? Write to jffs2 frequently will reduce flash life cycle.
I think it is fairly common to have a combination of devices:
/ (root) is a readonly flash device (mtd partition)
/etc is a writable flash device (mtd partition)
/tmp and /var are ramdisks (tmpfs), so they are writable, but lost when
power is cycled.
/Ricard
--
Ricard Wolf Wanderlöf ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
Phone +46 46 272 2016 Fax +46 46 13 61 30
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