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

From: Matthias Kaehlcke <[email-masked]>
Date: Tue, 19 Jan 2010 15:06:00 +0100

El Tue, Jan 19, 2010 at 02:17:22PM +0100 Ricard Wanderlof ha dit:

> On Tue, 19 Jan 2010, Johnny Hung wrote:
>
>> Okay, I think the steps is below if my rootfs is ramdisk and configure
>> files in jffs2,
>>
>> 1. cp /etc/* /mnt/mtd/etc/    (/mnt/mtd is my jffs2 fs)
>> 2. rm -rf /etc/*
>> 3. make symbolic links from all /etc/xx to /mnt/mtd/etc/xxx
>> 4. remake ramdisk rootfs
>>
>> It seems all files in ramdisk rootfs /etc all links to /mnt/mtd/etc/
>> and try to modify these files is effective after reboot.
>> But is this a common way in embedded linux ?
>
> In principle, but it is easier (and cleaner) to make a symbolic link from 
> (say) /etc -> /mnt/mtd/etc without linking every individual file and  
> directory.

i totally agree with ricard when you want to move the entire directory
to jffs2 and not only some selected files

> You could also use a jffs2 file system in flash for your rootfs, that way 
> you wouldn't need a ramdisk at all.

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.

-- 
Matthias Kaehlcke
Embedded Linux Developer
Barcelona

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