RFC: make init(8) aware of /rescue/sh

[Jilles Tjoelker]

On Wed, Feb 11, 2015 at 02:30:07AM -0800, Perry Hutchison wrote:
> Seems to me it might be desirable for init(8) to fall back
> to /rescue/sh for single-user mode if neither the default
> (kenv:init_shell) nor /bin/sh is usable.  Thoughts?

> (Patch generated against stable/8, but will likely apply to
> HEAD also -- not much has changed in init.)

> --- init.c-orig
> +++ init.c
> @@ -79,6 +79,9 @@
>  #include <login_cap.h>
>  #endif
>  
> +/* Ideally this value should come from the RESCUE side of paths.h */
> +#define	_PATH_R_BSHELL	"/rescue/sh"
> +
>  #include "pathnames.h"
>  
>  /*
> @@ -706,7 +709,8 @@
>  
>  		/*
>  		 * Fire off a shell.
> -		 * If the default one doesn't work, try the Bourne shell.
> +		 * If the default one doesn't work, try the Bourne shell;
> +		 * if that doesn't work either, try the rescue shell.
>  		 */
>  
>  		char name[] = "-sh";
> @@ -717,6 +721,8 @@
>  		emergency("can't exec %s for single user: %m", shell);
>  		execv(_PATH_BSHELL, argv);
>  		emergency("can't exec %s for single user: %m", _PATH_BSHELL);
> +		execv(_PATH_R_BSHELL, argv);
> +		emergency("can't exec %s for single user: %m", _PATH_R_BSHELL);
>  		sleep(STALL_TIMEOUT);
>  		_exit(1);
>  	}

It is already possible to type "/rescue/sh" at the prompt (the Makefile
always compiles with -DDEBUGSHELL). This must be done manually but also
covers the case where /bin/sh exists but rtld or shared libraries are
missing or broken.

I'm not really sure this is worth the extra code.

-- 
Jilles Tjoelker