busybox initramfs read only

jazzor · 11-13-2008, 10:25 PM

Hi. Im trying to construct a initramfs bootup, so far everything works fine except that the rootfs stays read only no matter what i do.

this is the start of the init script:

Code:

#!/bin/sh
export PATH=.:/bin:/sbin

mount -t proc proc /proc
mount -t sysfs sysfs /sys
mount -o remount,rw /

echo 0 >/proc/sys/kernel/printk
mdev -s

mkdir mountpoint
...

at the point where mdev -s is run, the filesystem is read only again and thus, it wont find the root device (since it cannot create /dev nodes).

Im using busybox 1.12.2.

Is there any particular configuration I need for busybox to make it mount read write all the time?

pinniped · 11-13-2008, 11:59 PM

Remember you probably do not have an fstab file at this point in time, not to mention 'mount' is provided by busybox and may have further limitations - such as not ever looking for a file like 'fstab' to parse.

So one problem is that you need to be more explicit about what is mounted and where. Of course, your '/dev' filesystem likely contains only 'console' and 'null' - which leads to a multitude of other problems.

What I would recommend is that you take apart an existing initramfs image and read through the init script. You will find (in most cases) that numerous other scripts are invoked to help set things up (doing things like providing your nice color entries as you see those "starting", "OK", and "failed" messages). Along the way, 'tmpfs' is used to create essential entries like the initial 'dev' filesystem. I can't explain everything in a post, so it's best to just read through those other existing init scripts and learn the details of how to set up dev, proc, udev, mount the root filesystem, pivot to the real init ...