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$FreeBSD: stable/10/sbin/mount/mount.conf.8 307403 2016-10-16 22:02:50Z sevan $
.Dd July 7, 2013 .Dt MOUNT.CONF 8 .Os .Sh NAME .Nm mount.conf .Nd root file system mount configuration file .Sh SYNOPSIS
a /.mount.conf .Sh DESCRIPTION During the bootup process, the .Fx kernel will try to mount the root file system using the logic in the .Fn vfs_mountroot function in
a src/sys/kern/vfs_mountroot.c . The root mount logic can be described as follows: l -enum t The kernel will synthesize in memory a config file with default directives for mounting the root file system. The logic for this is in .Fn vfs_mountroot_conf0 . t The kernel will first mount .Xr devfs 8 as the root file system. t Next, the kernel will parse the in-memory config file created in step 1 and try to mount the actual root file system. See .Sx FILE FORMAT for the format of the config file. t When the actual root file system is mounted, .Xr devfs will be re-mounted on the
a /dev directory. t If a
a /.mount.conf file does not exist in the root file system which was just mounted, the root mount logic stops here. t If a
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 .Sx FILE FORMAT for the format of the config file. t If the new root file system has a
a /.mount directory, the old root file system will be re-mounted on
a /.mount . t The root mount logic will go back to step 4. .El
p 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
a /.mount.conf file. .Sh FILE FORMAT The kernel parses each line in
a .mount.conf and then tries to perform the action specified on that line as soon as it is parsed. l -tag -width "XXXXXXXXXX" t Ic # A line beginning with a # is a comment and is ignored. t Ic {FS}:{MOUNTPOINT} {OPTIONS} The kernel will try to mount this in an operation equivalent to: d -literal -offset indent mount -t {FS} -o {OPTIONS} {MOUNTPOINT} / .Ed
p If this is successfully mounted, further lines in
a .mount.conf are ignored. If all lines in
a .mount.conf have been processed and no root file system has been successfully mounted, then the action specified by c .onfail is performed. t Ic .ask When the kernel processes this line, a .Li mountroot> command-line prompt is displayed. At this prompt, the operator can enter the the root mount. t Ic .md Ar file Create a memory backed .Xr md 4 virtual disk, using .Ar file as the backing store. t Ic .onfail Ar [panic|reboot|retry|continue] If after parsing all the lines in
a .mount.conf the kernel is unable to mount a root file system, the c .onfail directive tells the kernel what action to perform. t Ic .timeout Ar N Before trying to mount a root file system, if the root mount device does not exist, wait at most .Ar N seconds for the device to appear before trying to mount it. If c .timeout is not specified, the default timeout is 3 seconds. .El .Sh EXAMPLES The following example
a .mount.conf will direct the kernel to try mounting the root file system first as an ISO CD9660 file system on
a /dev/cd0 , then if that does not work, as an ISO CD9660 file system on
a /dev/acd0 , and then if that does not work, as a UFS file system on
a /dev/ada0s1a . If that does not work, a .Li 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. d -literal -offset indent .Li .onfail panic .Li .timeout 3 cd9660:/dev/cd0 ro .Li .timeout 0 cd9660:/dev/acd0 ro .Li .timeout 3 ufs:/dev/ada0s1a .Li .ask .Ed
p The following example
a .mount.conf will direct the kernel to create a .Xr md 4 memory disk attached to the file
a /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. d -literal -offset indent .Li .timeout 3 .Li .md /data/OS-1.0.iso .Li cd9600:/dev/md# ro .Li # Can also use cd9660:/dev/md0 ro .Ed
p The following example
a .mount.conf will direct the kernel to create a .Xr md 4 memory disk attached to the file
a /data/base.ufs.uzip and then mount the UFS file system on the md uzip device which was just created by the .Xr geom_uzip 4 driver. d -literal -offset indent .Li .md /data/base.ufs.uzip .Li ufs:/dev/md#.uzip ro .Li # Can also use ufs:/dev/md0.uzip ro .Ed
p The following example
a .mount.conf will direct the kernel to do a unionfs mount on a directory
a /jail/freebsd-8-stable which has a .Xr chroot 2 environment. d -literal -offset indent .Li .timeout 3 .Li unionfs:/jail/freebsd-8-stable .Ed .Sh NOTES For each root file system which is mounted, a
a /dev directory .Em must exist so that the root mount logic can properly re-mount .Xr devfs 8 . If this directory does not exist, the system may hang during the bootup process. .Sh SEE ALSO .Xr nmount 2 , .Xr md 4 , .Xr boot.config 5 , .Xr fstab 5 , .Xr boot 8 , .Xr loader 8 , .Xr mount 8 .Sh HISTORY The .Nm file first appeared in .Fx 9.0 . .Sh AUTHORS .An -nosplit The root mount logic in the .Fx kernel which parses
a /.mount.conf was written by .An Marcel Moolenaar Aq Mt marcel@FreeBSD.org . This man page was written by .An Craig Rodrigues Aq Mt rodrigc@FreeBSD.org .