MOUNT.CONF(8)						    BSD System Manager's Manual 					     MOUNT.CONF(8)

NAME

     mount.conf -- root file system mount configuration file

SYNOPSIS

     /.mount.conf

DESCRIPTION

     During the bootup process, the FreeBSD kernel will try to mount the root file system using the logic in the vfs_mountroot() function in
     src/sys/kern/vfs_mountroot.c.  The root mount logic can be described as follows:

     1.   The kernel will synthesize in memory a config file with default directives for mounting the root file system.  The logic for this is in
	  vfs_mountroot_conf0().

     2.   The kernel will first mount devfs(8) as the root file system.

     3.   Next, the kernel will parse the in-memory config file created in step 1 and try to mount the actual root file system.  See FILE FORMAT
	  for the format of the config file.

     4.   When the actual root file system is mounted, devfs will be re-mounted on the /dev directory.

     5.   If a /.mount.conf file does not exist in the root file system which was just mounted, the root mount logic stops here.

     6.   If a /.mount.conf file exists in the root file system which was just mounted, this file will be parsed, and the kernel will use this new
	  config file to try to re-mount the root file system.	See FILE FORMAT for the format of the config file.

     7.   If the new root file system has a /.mount directory, the old root file system will be re-mounted on /.mount.

     8.   The root mount logic will go back to step 4.

     The root mount logic is recursive, and step 8 will be repeated as long as each new root file system which is mounted has a /.mount.conf file.

FILE FORMAT

     The kernel parses each line in .mount.conf and then tries to perform the action specified on that line as soon as it is parsed.

     #		 A line beginning with a # is a comment and is ignored.

     {FS}:{MOUNTPOINT} {OPTIONS}
		 The kernel will try to mount this in an operation equivalent to:

		       mount -t {FS} -o {OPTIONS} {MOUNTPOINT} /

		 If this is successfully mounted, further lines in .mount.conf are ignored.  If all lines in .mount.conf have been processed and
		 no root file system has been successfully mounted, then the action specified by .onfail is performed.

     .ask	 When the kernel processes this line, a mountroot> command-line prompt is displayed.  At this prompt, the operator can enter the
		 the root mount.

     .md file	 Create a memory backed md(4) virtual disk, using file as the backing store.

     .onfail [panic|reboot|retry|continue]
		 If after parsing all the lines in .mount.conf the kernel is unable to mount a root file system, the .onfail directive tells the
		 kernel what action to perform.

     .timeout N  Before trying to mount a root file system, if the root mount device does not exist, wait at most N seconds for the device to
		 appear before trying to mount it.  If .timeout is not specified, the default timeout is 3 seconds.

EXAMPLES

     The following example .mount.conf will direct the kernel to try mounting the root file system first as an ISO CD9660 file system on /dev/cd0,
     then if that does not work, as an ISO CD9660 file system on /dev/acd0, and then if that does not work, as a UFS file system on /dev/ada0s1a.
     If that does not work, a mountroot> command-line prompt will be displayed where the operator can manually enter the root file system to
     mount.  Finally if that does not work, the kernel will panic.

	   .onfail panic
	   .timeout 3
	   cd9660:/dev/cd0 ro
	   .timeout 0
	   cd9660:/dev/acd0 ro
	   .timeout 3
	   ufs:/dev/ada0s1a
	   .ask

     The following example .mount.conf will direct the kernel to create a md(4) memory disk attached to the file /data/OS-1.0.iso and then mount
     the ISO CD9660 file system on the md device which was just created.  The last line is a comment which is ignored.

	   .timeout 3
	   .md /data/OS-1.0.iso
	   cd9600:/dev/md# ro
	   # Can also use cd9660:/dev/md0 ro

     The following example .mount.conf will direct the kernel to create a md(4) memory disk attached to the file /data/base.ufs.uzip and then
     mount the UFS file system on the md uzip device which was just created by the geom_uzip(4) driver.

	   .md /data/base.ufs.uzip
	   ufs:/dev/md#.uzip ro
	   # Can also use ufs:/dev/md0.uzip ro

     The following example .mount.conf will direct the kernel to do a unionfs mount on a directory /jail/freebsd-8-stable which has a chroot(2)
     environment.

	   .timeout 3
	   unionfs:/jail/freebsd-8-stable

NOTES

     For each root file system which is mounted, a /dev directory must exist so that the root mount logic can properly re-mount devfs(8).  If this
     directory does not exist, the system may hang during the bootup process.

SEE ALSO

     nmount(2), md(4), boot.config(5), fstab(5), boot(8), loader(8), mount(8)

HISTORY

     The mount.conf file first appeared in FreeBSD 9.0.

AUTHORS

     The root mount logic in the FreeBSD kernel which parses /.mount.conf was written by Marcel Moolenaar <marcel@FreeBSD.org>.  This man page was
     written by Craig Rodrigues <rodrigc@FreeBSD.org>.

BSD
								   July 7, 2013 							       BSD