Arch Linux

metalfan

Member

Registered: 2007-11-22

Posts: 99

cant mount root fs anymore

Hi,

ive mounted my rootfs from another system:

mount -t ext4dev /dev/sda7 /mnt/

back in the "old" system the kernel refuses to boot:

ext3-fs: unable to mount root filesystem because of unsupported optional features (40)         <-  probably not the exact message

im still able to mount the drive with the rescue cd, but after adding

MODULES="ext4dev"

to /etc/mkinit...  and pacman -S kernel26 the system still refuses to boot

any ideas?

sys info:
/dev/sda1 /boot  (ext2)
/dev/sda7 /

greets
metalfan

Last edited by metalfan (2007-11-23 22:07:07)

ckristi

Member

From: Bucharest, Romania

Registered: 2006-11-21

Posts: 225

Re: cant mount root fs anymore

Check your /etc/fstab and change ext3 with ext4dev where appropriate.
I guess this shoud be it.

Cristi

Last edited by ckristi (2007-11-23 22:18:32)

---

In love I believe and in Linux I trust

metalfan

Member

Registered: 2007-11-22

Posts: 99

Re: cant mount root fs anymore

how did arch read /etc/fstab if / wasnt mounted?

anyway, its set to ext4dev

Last edited by metalfan (2007-11-23 22:49:22)

ckristi

Member

From: Bucharest, Romania

Registered: 2006-11-21

Posts: 225

Re: cant mount root fs anymore

how did arch read /etc/fstab if / wasnt mounted?

anyway, its set to ext4dev

Well, I'm not a user of ext4, so I don't really get your problem.

Checking some brief specs on Wikipedia about ext4 I found this:
"Forward compatibility

The ext4 filesystem is forward compatible with ext3, that is, it can be mounted as an ext3 partition (using "ext3" as the filesystem type when mounting). However, if the ext4 partition uses extents (one of the major new features of ext4), forward compatibility and therefore the ability to mount the filesystem as ext3 is lost. Extents were enabled by default in the 2.6.23 kernel. Previously, the "extents" option was explicitly required (e.g. mount /dev/sda1 /mnt/point -t ext4dev -o extents).

So... do you have extents option set in fstab? It should read:

/dev/sda1               /            ext4dev      defaults,extents    0    0

The kernel is responsible with reading the fstab of the root filesystem before mounting / partition RW after init as well as RO to run init, as far as I know. And you set the root partition when you're configuring your boot loader. I think there's a problem with the ext4 module in kernel (which makes the kernel unable to mount / readonly to run init). Have you tried building your custom kernel with ext4 built in, not as a module?

Last edited by ckristi (2007-11-23 23:20:27)

---

In love I believe and in Linux I trust

metalfan

Member

Registered: 2007-11-22

Posts: 99

Re: cant mount root fs anymore

I dont think this is the case because i can mount the filesystem in question from another arch, both default 2.6.23 kernel.
And the mkinit... is generated from the modules in /lib/modules - which can mount my filesys.

Extents are enabled in /var/abs/core/base/kernel26/config.x86_64

CONFIG_EXT4DEV_FS_XATTR=y

greets
metalfan

Last edited by metalfan (2007-11-24 12:04:57)