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.Dd December 12, 2011
.Dt MKINITRD 8
.Os
.Sh NAME
.Nm mkinitrd
.Nd build an initial ramdisk image for use as early userland
.Sh SYNOPSIS
.Nm
.Op Fl b Ar bootdir
.Op Fl t Ar tmpdir
.Sh DESCRIPTION
The
.Nm
script builds a ramdisk (md) image based on the UFS filesystem containing
only the most basic tools, such as a minimal
.Xr init 8 ,
.Xr sh 1
as well as many
.Xr mount 8
utilities.
.Pp
It will also copy the contents of
.Pa /usr/share/initrd
onto the ramdisk, maintaining the same hierarchy.
.Pp
On completion, the final image will be copied to
.Pa /boot/kernel/initrd.img ,
ready to be used as an early userland.
The base directory for
.Pa kernel/initrd.img
can be changed with the
.Fl b
option to an optional
.Ar bootdir (the default is
.Pa /boot ) .
The temporary directory to be used for setting up the image can be specified
using the
.Fl t
option (the default is
.Pa /tmp ) .
.Pp
The
.Nm
script will read
.Pa /etc/mkinitrd.conf
if it exists and use the configuration from this file to override the
following variables (defaults are in
.Pa /etc/defaults/mkinitrd.conf ) :
.Bd -literal -offset indent
BUILD_DIR
INITRD_SIZE
BIN_TOOLS
SBIN_TOOLS
INITRD_DIRS
CONTENT_DIRS
.Ed
.Pp
Adding the following lines to
.Pa /boot/loader.conf
will enable the use of the created initrd image:
.Bd -literal -offset indent
initrd.img_load="YES"
initrd.img_type="md_image"
vfs.root.mountfrom="ufs:md0s0"
.Ed
.Pp
The format for vfs.root.realroot in
.Pa /boot/loader.conf
that allows the user to specify what system to mount as the
new root in the initrd is specified in its general form below:
.Bd -literal -offset indent
vfs.root.realroot="<type>:[arg1[:arg2[:argN]]]"
.Ed
.Pp
Currently, three types of real root are supported,
.Pa local ,
.Pa tcplay
and
.Pa crypt .
The
.Pa local
type allows to mount any local file system that does not require any
special setup apart from the initial discovery and calling the
.Pa mount
program. The general format is as follows:
.Bd -literal -offset indent
vfs.root.realroot="local:<FS TYPE>:<DEVICE PATH>[:<OPTIONS>]"
.Ed
.Pp
The
.Pa crypt
type allows to mount volumes supported by cryptsetup. The device will
be set up by prompting the user for his key, and this volume will then
be mounted as the new root.
.Bd -literal -offset indent
vfs.root.realroot="crypt:<FS TYPE>:<DEVICE PATH>:<VOLUME NAME>[:<OPTIONS>]"
.Ed
.Pp
The
.Pa tcplay
type allows to mount volumes supported by
.Xr tcplay 8 .
The device will be set up by prompting the user for his key, and this
volume will then be mounted as the new root.
.Bd -literal -offset indent
vfs.root.realroot="tcplay:<FS TYPE>:<DEVICE PATH>:<VOLUME NAME>[:<OPTIONS>]"
.Ed
.Sh EXAMPLES
.Bd -literal -offset indent
vfs.root.realroot="local:ufs:/dev/vg00/lv0[:OPTIONS]"
.Ed
.Bd -literal -offset indent
vfs.root.realroot="crypt:ufs:/dev/ad0s0a:secvolume[:OPTIONS]"
.Ed
.Sh SEE ALSO
.Xr md 4 ,
.Xr loader.conf 5
.Sh HISTORY
The
.Nm
command first appeared in
.Dx 2.7 .
.Sh AUTHORS
.Nm
was written by
.An Alex Hornung Aq ahornung@gmail.com .