Re: WARNING: expand-on-first boot might shrink your partition on Debian bookworm

[Henning Schild <henning.schild@siemens.com>]

Am Thu, 7 Jul 2022 09:48:22 +0200
schrieb Florian Bezdeka <florian.bezdeka@siemens.com>:

> Hi all,
> 
> here comes another Debian bookworm related problem. This time related
> to expand-on-first-boot, which destroys my image during the fist boot.
> 
> The linux-util packages has been updated and includes some changes
> related to partition alignment. See [1]. (Thanks Henning for pointing
> me here.) It might happen now that the last partition is shrinked
> instead of expanded.
> 
> This is especially relevant for setups where the last partition is the
> root partition and where no more space is available (e.g. booting up a
> wic image with qemu where disk size = image size)
> 
> The original partition table looked like this:
> 
> label: gpt
> label-id: 8CC4BCD4-F7B9-45F1-A066-DFB4068D6DFC
> device: /dev/sda
> unit: sectors
> first-lba: 34
> last-lba: 4554194
> sector-size: 512
> 
> After expand-on-first-boot it looks like that:
> (note the last-lba field)
> 
> label: gpt
> label-id: 5305C98F-17AD-4B41-9388-7DC319741C9D
> device: talker-debian-bookworm-qemuamd64.wic
> unit: sectors
> first-lba: 34
> last-lba: 4554320
> sector-size: 512
> 
> Booting up again stops in the initrd with the following error:
> 
> (initramfs) [    1.978569] EXT4-fs (sda2): bad geometry: block count
> 550586 exceeds size of device (550400 blocks)
> 
> resize2fs called from expand-last-partition.sh already throws a
> warning resize2fs: New size smaller than minimum (550586)
> 
> Ideas welcome...
> Taking over even more...

I think one idea as a quick hack in an affected layer could be to add
more EXTRA_SPACE, but i did not try that. With more space a slight
shrinking might just work. Or put a large fixes size in your wks ... or
play with alignment there to avoid shrinking.

And the good solution would probably to detect that the disk is already
"close to full" and simply step out early.

if /sys/class/block/sda/size - sum(/sys/class/block/sda/sda*/size) < 32M
echo "Nothing to do"; exit 0

Where 32M is made up, one should look up what the maximum shrink could
be. I think we could even say 4M. Or we could use percentage ... if sum
>= 0.95*size

Henning

> Best regards,
> Florian
> 
> 
> [1]
> https://github.com/util-linux/util-linux/commit/921c7da55ec78350e4067b3fd6b7de6f299106ee
>