[systemd-devel] [PATCH 07/11] Support init=/bin/bash on the kernel command line

[David Herrmann]

Hi

On Mon, Jun 16, 2014 at 2:42 PM, Dr. Werner Fink <werner at suse.de> wrote:
> On Fri, Jun 13, 2014 at 05:49:24PM +0200, Tom Gundersen wrote:
>> On Fri, Jun 13, 2014 at 4:41 PM, Werner Fink <werner at suse.de> wrote:
>> > From: Ruediger Oertel <ro at suse.de>
>> >
>> > Process 1 (aka init) needs to be started with an empty signal mask.
>> > That includes the process 1 that's started after the initrd is finished.
>> > When the initrd is using systemd (as it does with dracut based initrds)
>> > then it is systemd that calls the real init.  Normally this is systemd
>> > again, except when the user uses for instance "init=/bin/bash" on the
>> > kernel command line.
>>
>> Why is this necessary for /bin/bash, but not for /lib/systemd/systemd?
>> Please include the explanation in the commit message.
>
> I do not understand your question.  AFAIK the signal mask is set by
> systemd accordingly to man:systemd.service(5) ... the only problem
> with this schem is that /bin/bash nor any other shell does reset
> its signal mask.  I guess that systemd will support the init=/bin/bash
> on the kernel command line.  IMHO this requires a clean signal mask.

The question was, why is this fix related to init=/bin/bash? What does
bash do different than systemd that it requires this fix? That
information should be placed in the commit-message.

The fix itself looks good and if you called it "restore signal-mask
before executing init=" it'd be fine. However, calling it "support
init=/bin/bash" implies that this is only needed for init=/bin/bash.
This, however, is just a side-effect of this fix, because systemd
simply doesn't care for the initial sigmask.

I'll fix up the commit-msg and apply it. No need to resend.

Thanks
David