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

[Tom Gundersen]

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.

Cheers,

Tom

> ---
>  src/core/main.c |    9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git src/core/main.c src/core/main.c
> index d5d1ee2..c082354 100644
> --- src/core/main.c
> +++ src/core/main.c
> @@ -1831,6 +1831,7 @@ finish:
>          if (reexecute) {
>                  const char **args;
>                  unsigned i, args_size;
> +                sigset_t ss, o_ss;
>
>                  /* Close and disarm the watchdog, so that the new
>                   * instance can reinitialize it, but doesn't get
> @@ -1914,6 +1915,11 @@ finish:
>                  args[i++] = NULL;
>                  assert(i <= args_size);
>
> +                /* reenable any blocked signals, especially important
> +                 * if we switch from initial ramdisk to init=... */
> +                sigemptyset(&ss);
> +                sigprocmask(SIG_SETMASK,&ss,&o_ss);
> +
>                  if (switch_root_init) {
>                          args[0] = switch_root_init;
>                          execv(args[0], (char* const*) args);
> @@ -1932,6 +1938,9 @@ finish:
>                          log_error("Failed to execute /bin/sh, giving up: %m");
>                  } else
>                          log_warning("Failed to execute /sbin/init, giving up: %m");
> +
> +                /* back to saved state if reexec failed */
> +                sigprocmask(SIG_SETMASK,&o_ss,NULL);
>          }
>
>          if (arg_serialization) {
> --
> 1.7.9.2
>
> _______________________________________________
> systemd-devel mailing list
> systemd-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/systemd-devel