btrfs on kirkwood

[summers]

Hi,

Just installed arm arch on a ZyXEL NSA325. Some difficulties with the auto install, had to unplug the hdd, format and install image from another machine - but otherwise fine and easy.

Anyway was planning on converting the root fs to btrfs, mainly for the snapshots.

Updated to the latest version "packman -Sy -u", and /proc/filesystems contains the non nodev fs:

ext3
ext2
ext4
cramfs
vfat
msdos
fuseblk
f2fs

So doesn't seem to have btrfs compiled into the kernel. Which is suggested should be here:

https://wiki.archlinux.org/index.php/Btrfs

So I havn't yet converted the rootfs to btrfs. To save the hassle of reinstalling everything, can anyone confirm if btrfs is in the latest kirkwood kernel (3.16.2-1-ARCH)

Ta,

David.

[WarheadsSE]

You might want to be sure the bootloader can support btrfs

(hint, it doesn't)

[summers]

I was planning on keeping /boot as ext2 - it contains the uImage.

Uboot should be able to load the uimage, and start the kernel. So btrfs support is only needed when the linux kernel comes to mount the root fs. That is totally in the linux domain, and so shouldn't depend on uboot.

Am I missing something?

[summers]

AH solved. Its compiled as a module, and not loaded as default.

Means I'll need to create an initramdisk if btrfs is to be root ....

[summers]

Which takes me onto - quick scan of tools, and looks like arch is set up to use mkinitcpio - so presumably I just have to jump through those hoops. then link the cpio file into the kernel?

Must admit I've always done that in the past at the kernel compilation stage - I'll see if I can just do it for the default arm arch kernel, post compile ....

But not now - other things to get on with ...

[WarheadsSE]

uBoot can be used to load an uInitrd, or even an initrd.gz. All depends on the version you have, and what kind of kernel you are using.

[summers]

Yes - thats first on my list. For the uboot on the NSA325 work out what form of kernel image and ram disk it can take. Once that is answered; then can move onto how to create the relevent image on arch.

Oh yes notice its mentioned elsewhere, the pan to move to recenet uboot on armv5. Has this been done at all on kirkwood/NSA325?

When I've used uboot before (pandaboard) I've always rappidly switched to a very modern uboot, that can do device trees and things. My only experience with gzipped cpio file spaces, has been linking that directly into the kernel - for a very rapid boot into a very minimal filesystem.

[WarheadsSE]

I need to find time to do full testing and get the environment checked out, but we have it working entirely, yes.

Until such a time as an officially supported image exists, the existing u-boot requires uImage + uInitrd

[summers]

Guess I should update this thread.

On reflecting why I wanted to use btrfs, mainly to do backups on the NSA325, it occured to me that space was all important, but speed not so important. So decided to have the backups compressed with zlib.

Now btrfs is set up that the best and easiest way to do lib compression, is to set this as a mount option for the partition. This means that all new files get zlib compressed.

However, it doesn't make sense to zlib compress the arm arch OS - really want that to be avaiable asap.

So hence it made sense to have sepearte partitions for / and /home. So kept / as ext4, and changed /home to btrfs with zlib enabled.

This seems to do backups fine, so all working well.

Means I didn't need to jump through the initramfs image hoops - although having read up on this it didn't sound all that complex.