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MOUNT.CONF(5)		    BSD	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 di-
	  rectives for mounting	the root file system.  The logic for this is
	  in vfs_mountroot_conf0().

     2.	  The kernel will first	mount devfs(5) 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(5)	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/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 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/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) envi-
     ronment.

	   .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(5).  If this di-
     rectory 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			       October 17, 2013				   BSD

NAME | SYNOPSIS | DESCRIPTION | FILE FORMAT | EXAMPLES | NOTES | SEE ALSO | HISTORY | AUTHORS

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