Re: [chromeos-discuss] Mounting a CrOS partition from Linux

[James Heather]

On Fri, 7 Jan 2022, 21:33 James Heather, <jamesh...@google.com> wrote:

+chromium-os-dev

chromeos-discuss to bcc

Thanks, Mike! Is there a way of mounting r/w?

On Fri, 7 Jan 2022, 21:12 Mike Frysinger, <vap...@google.com> wrote:

assuming when you say "CrOS partition" you mean "the CrOS rootfs", use -o ro

if you have more questions like this, i'd recommend go/chromium-os-dev instead

-mike

On Fri, Jan 7, 2022 at 4:07 PM James Heather <jamesh...@google.com> wrote:

How can I mount a CrOS partition from a Linux box?

It seems to report as ext2, but mount refuses to recognise it.

James

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[Mike Frysinger]

you can, but now i question what it is exactly you're trying to do.  modifying a rootfs that has verification enabled will usually lead to it not booting.

so can you please back up a bit and describe in detail what you're trying to do ?  the answer for you might be to change something earlier in your process.

-mike

[James Heather]

I have an installer image, and I want to use that image, but I want to tweak the partition sizes. Specifically, I want a bigger EFI partition. I could modify the partition layout after the fact, which is definitely doable but not trivial because it's not the last partition. I could perhaps rebuild the image, but it seemed easier to me to edit that one file so that it would create a bigger partition from the start.

[Mike Frysinger]

what is an "installer image"? do you mean a recovery image?

why do you need to edit the rootfs to change the EFI partition? the recovery initramfs is responsible for initializing the GPT on the disk.

-mike

[Mike Frysinger]

assuming you're actually talking about a recovery image ...

i double checked the code, and it looks like the recovery initramfs mounts the rootfs and executes `chromeos-recovery` out of the rootfs to do the partitioning, so it would use the write_gpt.sh from the rootfs.

that said, the end result would still have a modified rootfs installed once the recovery image finishes.

so it's unclear if you're creating the recovery image yourself, or you're grabbing a release one and trying to hack it yourself.  the tools for making these kind of tweaks are readily available if you're building your own image, but not if you're hacking one.  it's possible, but it's not really documented.

-mike