Suggestions for: disk-format#TOC-Changing-the-kernel-command-line

[Marc Herbert]

Hi,

 Two suggestions for the (very useful) http://www.chromium.org/chromium-os/chromiumos-design-docs/disk-format#TOC-Changing-the-kernel-command-line

1. Just before the last line where the kernel partition is destr... replaced with kernel.new, suggest running this command as a last minute sanity check:

  butil_kernel --verify /tmp/kernel.new --verbose 

2. I'm under the impression that this section requires running this first?

  /usr/share/vboot/bin/make_dev_ssd.sh --remove_rootfs_verification --partitions 2

If this is indeed required then it should be mentioned.

Cheers,

Marc

PS: NOT a suggestion for the page but replacing kernel.old with a more direct /dev/sdb2 does not seem to cause any problem.

[Marc Herbert]

Third suggestion: rephrase slightly this sentence:

"For the recovery kernel on a removeable device <private_key> above is recovery_kernel_data_key.vbprivk and for the main kernel on the hard drive the<private_key> is kernel_data_key.vbprivk."

... since it leaves unclear the case of: a main kernel on a removable device.

Generally speaking, I find the correctness of this section to matter more than usual since the penalty for most mistakes is quite big (not booting!)

[Mike Frysinger]

i've added (1) now

iiuc, (2) is merely a shortcut to editing the kernel command line such that rootfs verification is disabled.  that's orthogonal to modifying the kernel command line yourself.

-mike

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[Hung-Te Lin]

No, you don't need to call make_dev_ssd before changing kernel.

However, make_dev_ssd itself supports changing kernel command line on-the-fly.

See the --save_config and --set_config options.

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[Marc Herbert]

2015-02-26 23:49 GMT-08:00 Mike Frysinger <vap...@chromium.org>:

i've added (1) now

1. Thanks Mike! However I'm afraid you've added this line just one step too early :-(

2.. I did not realize about make_dev_ssd "config" features, thanks Hung-Te, will try them ASAP. Isn't this feature overlap another, completely different reason to briefly mention make_dev_ssd  in the same page?

3. Any comment about suggestion (3) in my other email? Maybe just drop "removeable device" and "hard drive" from the sentence.

Cheers,

Marc

[Mike Frysinger]

(1) should be fixed up, thanks

-mike

[Marc Herbert]

On Friday, 27 February 2015 00:05:32 UTC-8, Hung-Te Lin wrote:

No, you don't need to call make_dev_ssd before changing kernel.

OK, I think I got where my confusion came from: when used on a USB stick, make_dev_ssd switches it from recovery key to "main kernel" key. Correct?

Since I did not know about this key switch I was always using the same --signprivate "main kernel" key, so changing the kernel config with vbutil_kernel was only working after I used make_dev_ssd and switched key.

At least that's what vbutil_kernel --verify kernel.new seems to tell me.

 

However, make_dev_ssd itself supports changing kernel command line on-the-fly.

See the --save_config and --set_config options.

... and it's faster and much less error-prone than vbutil_kernel, thanks again. I probably won't look again at this page I was making suggestions for.

Marc.

[Bill Richardson]

On Fri, Feb 27, 2015 at 1:17 PM, Marc Herbert <marc.h...@gmail.com> wrote:

OK, I think I got where my confusion came from: when used on a USB stick, make_dev_ssd switches it from recovery key to "main kernel" key. Correct?

​Unless you give it the --recovery_key ​arg, yes.

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[Marc Herbert]

On Friday, 27 February 2015 00:05:32 UTC-8, Hung-Te Lin wrote:

However, make_dev_ssd itself supports changing kernel command line on-the-fly.

See the --save_config and --set_config options.

Even better, this is documented... if you already know what you're looking for:

http://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/cr-48-chrome-notebook-developer-information/how-to-boot-ubuntu-on-a-cr-48#TOC-Configure-the-kernel

Just for the record.

[Hung-Te Lin]

FYI I've just merged a new option --edit_config so editing-in-place should be easier than ever.

https://chromium-review.googlesource.com/#/c/266814/

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[Marc Herbert]

On Wednesday, April 22, 2015 at 9:05:32 PM UTC-7, Hung-Te Lin wrote:

FYI I've just merged a new option --edit_config so editing-in-place should be easier than ever.

https://chromium-review.googlesource.com/#/c/266814/

I love this, thank you!