Re: Possible to redirect real init's message to netconsole?
On Wed, Feb 3, 2016 at 2:18 AM, Roger Shimizu <rogershimizu@gmail.com> wrote:
> Dear Ben,
>
> On Wed, Feb 3, 2016 at 2:00 AM, Ben Hutchings <ben@decadent.org.uk> wrote:
>> On Wed, 2016-02-03 at 01:50 +0900, Roger Shimizu wrote:
>>> Dear initramfs-tools maintainer,
>>>
>>> By command "exec >/dev/kmsg 2>&1" in init, which was introduced by
>>> commit 3acddc [0], kernel messages can all redirected to netconsole
>>> with no problem.
>>>
>>> I want some bit more, that to redirect service start/stop messages
>>> from sysvinit/systemd to netconsole as well.
>>>
>>> I already tried to replace ">${rootmnt}/dev/console" with
>>> ">${rootmnt}/dev/kmsg" in the final block of "init" script, but with
>>> no luck.
>>> I'm now wondering whether it's possible under initramfs-tools.
>>> Maybe the right way is to hack systemd/sysvinit?
>>>
>>> [0]: https://anonscm.debian.org/cgit/kernel/initramfs-tools.git/commit/?id=3acddcce9763192ffd169b32a511542adf1282f2
>>
>> run-init resets the standard error streams. You could try adding
>> "-c /dev/kmsg" to the run-init command line.
>
> Thanks for your feedback!
>
> However, I add "-c /dev/kmsg", and the command looks like:
> exec run-init -c /dev/kmsg ${drop_caps} ${rootmnt} ${init} "$@"
> <${rootmnt}/dev/console >${rootmnt}/dev/console 2>&1
>
> The result is kernel panic:
>
> [ 8.064410] Kernel panic - not syncing: Attempted to kill init!
> exitcode=0x00000100
> [ 8.064410]
> [ 8.073562] CPU: 0 PID: 1 Comm: run-init Not tainted
> 3.16.0-4-kirkwood #1 Debian 3.16.7-ckt20-1+deb8u3
> [ 8.082889] [<c00100c4>] (unwind_backtrace) from [<c000c45c>]
> (show_stack+0x18/0x1c)
> [ 8.090642] [<c000c45c>] (show_stack) from [<c03abda0>] (panic+0x80/0x1f8)
> [ 8.097536] [<c03abda0>] (panic) from [<c001bcac>] (do_exit+0x470/0x884)
> [ 8.104253] [<c001bcac>] (do_exit) from [<c001c0fc>] (do_group_exit+0x0/0xb4)
> [ 8.111396] [<c001c0fc>] (do_group_exit) from [<c0009400>]
> (ret_fast_syscall+0x0/0x34)
I guess it's because /dev/kmsg is simply not a console device.
What I need is a console device of netconsole, so I find one patch
[1], which unfortunately is finally rejected, however it mentioned
"ttyprintk" at last.
After tracing a bit, and find ttyprintk has been made as module
[2][3], but debian kernel doesn't enable it yet.
Do I need submit a ticket to include this feature? Or mailing list
discussion/request is fine?
[1]: https://patchwork.ozlabs.org/patch/336410/
[2]: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=7d1c28
[3]: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=b24313
Cheers,
--
Roger Shimizu, GMT +9 Tokyo
PGP/GPG: 17B3ACB1
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