Re: [PATCH 2/7] release/combined: Compress installation image

Demi Marie Obenour
2025-11-01T22:15:59Z

[-- Attachment #1.1.1: Type: text/plain, Size: 2518 bytes --]

On 10/29/25 12:51, Alyssa Ross wrote:
> Alyssa Ross <hi@alyssa.is> writes:
>
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>
>>> This will be needed once the B partitions are added. Otherwise,
>>> tar2ext4's size limit is exceeded.
>>>
>>> The timeout is increased to account for the very slow compression
>>> process.
>>>
>>> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
>>> ---
>>> release/checks/integration/meson.build | 2 +-
>>> release/combined/eosimages.nix | 14 +++++++++-----
>>> 2 files changed, 10 insertions(+), 6 deletions(-)
>>
>> I haven't built this yet, so maybe I'm wrong somehow, but doesn't this
>> break "Try Spectrum"? GRUB isn't going to be able to loopback mount a
>> compressed image, I assume. That's why I keep asking what GNOME OS
>> does. We currently produce an image that lets you install Spectrum, or
>> try it out in a live image. Do they do that too? If so, how do they
>> make it so that live image is bootable without being huge? Does their
>> installer resize partitions, perhaps?
>>
>> (I reviewed the rest of the patch anyway, but I think we're going to
>> need a different approach here.)
>
> Okay, I've finally got the answers I wanted about the GNOME OS installer
> on Matrix. It sounds like it doesn't copy a whole disk image like
> eos-installer does; rather it copies individual partition images using
> systemd-repart. This means they can distribute small partition images,
> and install them into partitions with room to grow, which would solve
> this problem.
>
> Reusing GNOME OS's installer sounds like it would be good then, but I
> don't know how much work it would be, and don't want to block this work
> on that, so I suggest we go ahead with uncompressed, small partitions
> for now — either sized to content or slightly bigger than content — and
> then later on we switch to GNOME OS's installer, and then increase the
> sizes of the installed partitions. Only at that point would we consider
> Spectrum installs "stable".

I agree in the long term, but I found a short-term workaround: use
erofs instead of ext4. That compresses the giant runs of zeros down
to almost nothing, and its mkfs tool doesn't have the same file size
limitations. The only difficulty is that if we should have dm-verity
protection in the installer for ext4, we _really_ ought to have it
for erofs. That's a separate change, though.
--
Sincerely,
Demi Marie Obenour (she/her/hers)

[-- Attachment #1.1.2: OpenPGP public key --]
[-- Type: application/pgp-keys, Size: 7253 bytes --]

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]