[Odroid XU4] no overlayfs

Petr StehlÃk · September 20, 2016

The ChangeLog of Armbian says that overlayfs was added in V5.15. I got installed V5.20 (or actually an earlier and then apt-get upgraded) yet the overlayfs is not available (kernel 3.10.103-odroidxu4). I have even tried installing linux-*-next and *uboot*-next (not even knowing what the -next mean) but it didn't help, still no overlayfs in /proc/filesystems.

Also, on reboot the Odroid is missing LAN connection randomly. It can be fixed by running dhclient manually but then the ethernet card is named by systemd. Normally it's eth0 and the networking works. I couldn't figure out what is the root cause of this issue, it seems random. I have also read in a ChangeLog that this got fixed long time ago. (?)

Please help. I'd like to end up with a read-only root and the overlayfs seemed like the best option for that. I just don't understand the difference between the ChangeLog and my exprience.

Thanks,

Petr

wildcat_paris · September 20, 2016

@Petr

~~I have little idea but I read overlayfs was available with kernel 3.18 (any backport to 3.10?)~~

https://en.wikipedia.org/wiki/OverlayFS

it looks there is CONFIG_OVERLAYFS_FS=m for legacy 3.10

https://github.com/igorpecovnik/lib/blob/master/config/kernel/linux-odroidxu4-default.config

so check if you can load the kernel module

--

"next" is vanilla kernel (recent) but for XU4 it is still experimental for Armbian

just see http://forum.armbian.com/index.php/topic/2005-patching-the-kernel/

currently the default 'next' kernel config has # CONFIG_OVERLAY_FS is not set

(try to load the legacy kernel module first please)

Petr StehlÃk · September 20, 2016

Oh well, sudo modprobe overlayfs indeed adds the overlay filesystem to /proc/filesystems. I am so used to automagic loading of modules that I didn't think of this. My fault.

Thank you, goldfish_paris!

Though adding "overlayfs" to /etc/modules didn't help the overlayroot package to start working correctly. Something else is wrong.

wildcat_paris · September 20, 2016

I know almost nothing on overlayfs

https://spin.atomicobject.com/2015/03/10/protecting-ubuntu-root-filesystem/

I don't know your usage / usecase

but you may need tweaking your initrd/initramfs

Petr StehlÃk · September 21, 2016

I just followed the article you happened to link as well. There's no word about tweaking initramfs, it should all happen automatically. The goal is simple - read-only rootfs, to save the "disk" from wearing out.

wildcat_paris · September 21, 2016

humm... unless you are named Noah, nothing happens automagically

Petr StehlÃk · September 21, 2016

Then everybody using Ubuntu on PC is named Noah. You see? I'd think it's an incompatibility in Armbian of some sort but I am not skilled enough to debug systemd based initramfs issues.