Re: mount ramdisk rootfs /etc directory to jffs2 filesystem.

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Johnny Hung wrote:
2010/1/22 Marco Stornelli <marco.stornelli@xxxxxxxxx>:
2010/1/22 Johnny Hung <johnny.hacking@xxxxxxxxx>:
2010/1/20 Marco Stornelli <marco.stornelli@xxxxxxxxx>:
2010/1/20 Johnny Hung <johnny.hacking@xxxxxxxxx>:
2010/1/19 Matthias Kaehlcke <matthias@xxxxxxxxxxxx>:
El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:

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.
Another query, does the syslogd/klogd log files also store in jffs2
rootfs? Write to jffs2 frequently will reduce flash life cycle.

BRs, H. Johnny
--
It seems there are a lot of file-systems I have to study :P. The same
question is
how to split my rootfs? Re-mount /etc, /var to another file-sysyem mtd part when
system boot up?

Yes, I know. So if I want set etc directoyr to /dev/mtd5 not in rootfs
/, I need to add "/dev/mtdblock5  /etc        jffs2   defaults
0       0" in /etc/fstab file but rootfs doesn't contain /etc
directory because /etc directoyr is store in /dev/mtdblock5.
Do you know what I mean? The kernel execute /sbin/init after mount
rootfs and /sbin/init is link to busybox, busybox will read
/etc/inittab file to initial. The problem is coming, how busybox to
read /etc in rootfs before mount /dev/mtdblock5 to /etc? There is no
program to mount /dev/mtdblock5 to /etc before busybox init execute.

I think I must mistake some concept, please give me a hint.
Thank you
BRs, H. Johnny


You have two /etc directories: one in the the read-only root file system and one in the jffs2 fs. In the root fs you have /etc/fstab, /etc/inittab and any scripts it may call. The init program will mount /dev/mtdblock5 over the top of the /etc that is in the rootfs, so giving you the read/write version of /etc. Any files open in the old /etc - e.g. /etc/inittab - will continue to be open, but any new files opened in /etc will use the read/write version in jffs2. You can also do some interesting things with symbolic links... This technique works. I have used it in several projects.

--
Chris Simmonds                   2net Limited
chris@xxxxxxxxxx                 http://www.2net.co.uk/

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