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MOUNT.CONF(5)		       File Formats Manual		   MOUNT.CONF(5)

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 direc-
	  tives for mounting the root file system.  The logic  for  this  is  in
	  vfs_mountroot_conf0().

     2.   The kernel will first mount devfs(4) 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(4)  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 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 un-
		 able  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 speci-
		 fied, 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/cd1,  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  op-
     erator  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/cd1 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)	environ-
     ment.

	   .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(4).	If  this  direc-
     tory 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  writ-
     ten by Craig Rodrigues <rodrigc@FreeBSD.org>.

FreeBSD 15.1			October 17, 2013		   MOUNT.CONF(5)
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