Subject: Re: The smallest multi-user system
To: <>
From: Brian Rose <>
List: current-users
Date: 08/14/2003 23:26:52
Jeremy C. Reed wrote: 
> In /usr/src/sbin/init/init.c:
>         if ((session_db = dbopen(NULL, O_RDWR, 0, DB_HASH, NULL)) == 0) {
>                 emergency("session database open: %m");
>                 return (1);
>         }
> (Then when that "start_session_db()" fails, init does the single_user
> instead of multi_user.)

Should I see the emergency() message on the console (i386)?

> Again, I don't know if dbopen(NULL, ...) uses memory or disk for the
> temporary database. But now, I think I am wrong, because looking at
> src/lib/libc/db/hash/hash.c doesn't indicate any opening of files with it
> is NULL.

The man page has this to say...

       Dbopen opens file for reading and/or writing.  Files never
       intended to be preserved on disk may be created by setting
       the file parameter to NULL.

Is it possible that init is failing elsewhere? 

I just noticed the function mfs_dev() which is called if MFS_DEV_IF_NO_CONSOLE is defined, which it is. 
        /* Mount an mfs over /dev so we can create devices */
	switch ((pid = fork())) {
	case 0:
		(void)execl("/sbin/mount_mfs", "mount_mfs", "-i", "192",
		    "-s", "768", "-b", "4096", "-f", "512", "swap", "/dev",

	case -1:

		if (waitpid(pid, &status, 0) == -1)
		if (status != 0)

Please correct my line of thinking...

init() forks to mount the ramdrive. The child process would execute and then exit with a return code of 1. The parent process would get this on the waitpid line and return -1 and status would be set to 1, which would force the system into single user mode due to the following code...

    if (mfs_dev() == -1)
	requested_transition = single_user;

It looks like all systems with a ramdrive would always go to single user. Correct? Has anyone made a multiuser system that boots off of a ramdrive?

Any more ideas?


While looking for the sources for mount_mfs (there are none in /usr/src/sbin) I found the source for the man page is in /usr/src/sbin/newfs. I also noticed that the mount_mfs file size is exactly the same size as newfs. The Makefile for newfs has the following line...

LINKS=	${BINDIR}/newfs ${BINDIR}/mount_mfs

It looks like newfs and mount_mfs are one in the same. Anyway, I added them to my system and I still fall into single-user mode.

Note: I can type exit at the prompt which brings me to the login prompt where I can login normally.