> 
> B/3 would probably enter single user mode. At least I think setting bit 1 
> of R5 means single user mode for unices on the vax.
> 
Look at the NetBSD/vax FAQ :-) These codes are common for all vax unixes,
it's stored in the "howto" word.


http://vaxine.bitcon.no/section5.html#ss511



5.11 Which bootflags can I give to the boot loader?

A: Lots. The following is an extract from a message from Bertram Barth <bertram@gummo.bbb.sub.org> (again!) to me:

------------------- Begin included message -------------------------------

    Bootflags are used to give information about how to boot
    (eg. single-user, ask-for-filename) to the /boot program.
    Bootflags can be combined by adding/or-ing their values.
    They are specified via the boot-command from console prompt:

        >>> b/43 dua0

    specifies the value 0x43 to be placed in register R5 which is 
    later copied to register R11 and evaluated by /boot.
    In this example the value 0x43 expands to  RB_ASKNAME | RB_SINGLE | RB_KDB

    Valid flags are (not all of them are evaluated):
    [for the most recent list look in /usr/include/sys/reboot.h]

#define RB_ASKNAME      0x001   /* ask for file name to reboot from */
#define RB_SINGLE       0x002   /* reboot to single user only */
#define RB_NOSYNC       0x004   /* dont sync before reboot */
#define RB_HALT         0x008   /* don't reboot, just halt */
#define RB_INITNAME     0x010   /* name given for /etc/init (unused) */
#define RB_DFLTROOT     0x020   /* use compiled-in rootdev */
#define RB_KDB          0x040   /* give control to kernel debugger */
#define RB_RDONLY       0x080   /* mount root fs read-only */
#define RB_DUMP         0x100   /* dump kernel memory before reboot */
#define RB_MINIROOT     0x200   /* mini-root present in memory at boot time */

------------------- End included message ---------------------------------


-- Ragge