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Originally Posted by Amboss View Post
One thing I found out lately: dmesg gives me a unsupported option (100). I guess the btrfs created on my laptop is not compatible with the old 3.16, so it won't mount. In the end this might cause the errors being created on first reboot, when J1 tries to repair automatically?
Yup, definitely.

Format it with (where <uuid> is the UUID of the old partition, or alternatively, let btrfs generate a new UUID and upgrade your /etc/fstab file) :
mkfs.btrfs -d single -m single -n 4096 -L sailfish -O ^extref,^skinny-metadata -U <uuid>
That should do it.

The kernel onboard of the Jolla 1 is a tiny bit old.
As such it doesn't support some feature that later versions of BTRFS have enabled by default.
If you generate it on a laptop/desktop your BTRFS will be way too modern.
If you generate it on device, the btrfs-tools are a tiny bit more modern too (3.16 instead of 3.4).

Details :
  • -n / --nodesize : it used to be 4096 by default on older (<= 3.11), nowadays (>= 3.12) it's 16k
  • -O / --features : that the most critical part
    • ^ext-ref : It's default on on 3.16 (e.g.: btrfs-tools on jolla), but it's not available before 3.7 (like on the jolla)
    • ^skinny-metadata : it's default on with 3.18 (like on your desktop) but it's not available before 3.10 (like on the jolla)
  • -d / --data and -m / --metadata : although it's not mandatory, it helps a lot on space-constrained devices like the Jolla.
  • -L / --label : it's fixed with "sailfish"
  • -U / --uuid : Sailfish identifies and mounts the partitions based on UUID. The one of the partition must match the one in /etc/fstab

More information about features in BTRFS :
> mkfs.btrfs -O list-all
Filesystem features available:
mixed-bg            - mixed data and metadata block groups (0x4, compat=2.6.37, safe=2.6.37)
extref              - increased hardlink limit per file to 65536 (0x40, compat=3.7, safe=3.12, default=3.12)
raid56              - raid56 extended format (0x80, compat=3.9)
skinny-metadata     - reduced-size metadata extent refs (0x100, compat=3.10, safe=3.18, default=3.18)
no-holes            - no explicit hole extents for files (0x200, compat=3.14, safe=4.0)

I do not have a publicly writable storage for file transfer. Will see, if I can get a ftp server running temporarily.
I'll MP.

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