Root partition cannot be mounted rw [Solved]

Pajaro · 2014-12-20 16:30:39

Since last update, my root partition cannot be mounted rw. dmesg shows:

changing journal_checksum during remount not supported

everytime I try to run:

mount -o remount,rw /

I tried using options "remount,rw,journal_checksum" with the same result.

If I run:

tune2fs -o journal_checksum /dev/sda3

it complains with:

Invalid mount option set: journal_checksum

Many other mount options are not accepted by tune2fs, but other options such as "acl" work.

The output of "mount" command is:

/dev/sda3 on / type ext4 (ro,relatime,data=ordered)

but my fstab has the following options:

/dev/sda3               /               ext4            rw,noatime,discard,acl,auto_da_alloc,journal_checksum,commit=20,data=ordered    0 2

What can I do?

Thank you

Last edited by Pajaro (2014-12-21 08:47:03)

olive · 2014-12-20 17:04:52

Try to boot from a rescue CD (or USB stick) (the systemrescuecd or the iso archlinux install CD) and do a fsck -f /dev/sd<your device>. Then try to mount your root partition manually from there. You have many options in your fstab, are you sure they are valid? What if you remove all of these obscure options? I have only "rw,relatime,data=ordered"

Last edited by olive (2014-12-20 17:06:24)

Pajaro · 2014-12-20 19:00:20

olive wrote:

Try to boot from a rescue CD (or USB stick) (the systemrescuecd or the iso archlinux install CD) and do a fsck -f /dev/sd<your device>. Then try to mount your root partition manually from there. You have many options in your fstab, are you sure they are valid? What if you remove all of these obscure options? I have only "rw,relatime,data=ordered"

Acessing with systemrescuecd and removing journal_checksum and auto_da_alloc from fstab fixed the situation. I don't know which was the one causing the trouble, but I assume it must have been journal_checksum.

Thank you!

jasonwryan · 2014-12-20 19:13:00

Please remember to mark your thread as [Solved] by editing your first post and prepending it to the title.

Spider.007 · 2014-12-20 21:58:02

Looking at http://lwn.net/Articles/351019/; it seems that option is deprecated for some time. I wonder how that option got into your fstab?

Last edited by Spider.007 (2014-12-21 11:48:58)

Pajaro · 2014-12-21 08:57:55

jasonwryan, done.

Spider.007, wow, the patch is years older than my installation xD

slicky.dvl · 2015-01-15 12:41:48

Spider.007 wrote:

Looking at http://lwn.net/Articles/351019/; it seems that option is deprecated for some time.

That patch seems to have been reverted later on. (At least journal_checksum option is still present in Documentation/filesystems/ext4.txt.) So, IMO, removing journal_checksum option will actually disable journal checksumming.

The initial problem seems to be as follows:

The initrd mounts the root with just ro or rw (i.e. without checksumming).
Later, systemd applies the rootfs' flags from /etc/fstab via a remount, which is blocked in the new kernel by a recenlty added patch.

So, you can either:

remove journal_checksum from /etc/fstab (which, IMO, is a bad idea); or
add journal_checksum to initial mount options that are used by initrd.

The latter could be achieved by adding rootflags=journal_checksum to the kernel parameters. (Those are parsed and interpreted by the initrd's init script. The rootflags are used here.)

Pajaro · 2015-01-15 15:56:20

slicky.dvl wrote:

So, you can either:
remove journal_checksum from /etc/fstab (which, IMO, is a bad idea); or
add journal_checksum to initial mount options that are used by initrd.
The latter could be achieved by adding rootflags=journal_checksum to the kernel parameters. (Those are parsed and interpreted by the initrd's init script. The rootflags are used here.)

I have reenabled journal_checksum and added rootflags=journal_checksum to the kernel parameters. It works. Thank you for sharing this information.

Arch Linux

#1 2014-12-20 16:30:39

Root partition cannot be mounted rw [Solved]

#2 2014-12-20 17:04:52

Re: Root partition cannot be mounted rw [Solved]

#3 2014-12-20 19:00:20

Re: Root partition cannot be mounted rw [Solved]

#4 2014-12-20 19:13:00

Re: Root partition cannot be mounted rw [Solved]

#5 2014-12-20 21:58:02

Re: Root partition cannot be mounted rw [Solved]

#6 2014-12-21 08:57:55

Re: Root partition cannot be mounted rw [Solved]

#7 2015-01-15 12:41:48

Re: Root partition cannot be mounted rw [Solved]

#8 2015-01-15 15:56:20

Re: Root partition cannot be mounted rw [Solved]

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