path: root/sbin/mount_vnd/mount_vnd.8

.\"	$OpenBSD: mount_vnd.8,v 1.6 2007/05/27 03:47:09 jmc Exp $
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.\"     @(#)vnconfig.8	8.1 (Berkeley) 6/5/93
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.\" Copyright (c) 2007 Alexander von Gernler <grunk@openbsd.org>
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.Dd May 18, 2007
.Dt MOUNT_VND 8
.Os
.Sh NAME
.Nm mount_vnd ,
.Nm vnconfig
.Nd "configure vnode disks for file swapping or pseudo file systems"
.Sh SYNOPSIS
.Nm mount_vnd
.Bk -words
.Op Fl k
.Op Fl K Ar rounds
.Op Fl o Ar options
.Op Fl S Ar saltfile
.Ar image
.Ar vnd_dev
.Ek
.Nm vnconfig
.Bk -words
.Op Fl ckluv
.Op Fl K Ar rounds
.Op Fl S Ar saltfile
.Ar vnd_dev
.Ar image
.Ek
.Sh DESCRIPTION
The
.Nm vnconfig
command configures vnode pseudo disk devices.
It will associate (or disassociate) the special file
.Ar vnd_dev
with the regular file
.Ar image ,
allowing the latter to be accessed as though it were a disk.
Hence a regular file within the file system can be used for swapping
or can contain a file system that is mounted in the name space.
.Pp
Both traditional devices,
.Xr vnd 4 ,
and the cache-coherent devices,
.Pa svnd ,
are configured through
.Nm vnconfig .
.Pa svnd
should be mounted with the
.Xr mount 8
option
.Dq sync
if
.Ar image
is being read from,
to ensure consistency in the buffer cache.
For normal operation this is not necessary.
.Pp
.Nm mount_vnd
works similarly to
.Nm vnconfig ,
but it provides an interface that can be used by the
.Xr fstab 5
infrastructure, so that an
.Ar image
file can be configured to a device
.Ar node
while booting.
.Pp
.Nm mount_vnd
is invoked by
.Xr mount 8
when using the following syntax:
.Bd -ragged -offset 4n
.Nm mount Op options
-t vnd
.Ar image Ar node
.Ed
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl c
.Nm vnconfig
only.
Configures the device.
If successful, references to
.Ar vnd_dev
will access the contents of
.Ar image .
This is the default operation.
.It Fl K Ar rounds
Associate an encryption key with the device.
All data will be encrypted using the Blowfish cipher before it is
written to the disk.
The user is asked for both a passphrase and the name of a salt file.
The salt file can also be specified on the command line using the
.Fl S
option.
The passphrase and salt are combined according to PKCS #5 PBKDF2 for the
specified number of
rounds to generate the actual key used.
.Ar rounds
is a number between 1000 and
.Dv INT_MAX .
DO NOT LOSE THE SALT FILE.
Encryption only works with
.Pa svnd .
.It Fl k
Associate an encryption key with the device.
All data will be encrypted using the Blowfish cipher before it is
written to the disk.
Encryption only works with
.Pa svnd .
.It Fl l
.Nm vnconfig
only.
List the (s)vnd devices and indicate which ones are in use.
If a specific
.Ar vnd_dev
is given, then only that one will be described.
.It Fl o Ar options
.Nm mount_vnd
only.
Options are specified with a
.Fl o
flag followed by a comma separated string of options.
See the
.Xr mount 8
man page for possible options and their meanings.
.Pp
At the moment,
.Fl o
is only here for compatibility reasons, but no use is made of supplied
options.
.It Fl S Ar saltfile
When
.Fl K
is used, specify the
.Pa saltfile .
If the salt filename is not specified using
.Fl S ,
it defaults to
.Ar image Ns .slt .
.It Fl u
.Nm vnconfig
only.
Unconfigures a
.Ar vnd_dev .
.It Fl v
.Nm vnconfig
only.
Print messages to stdout describing actions taken.
.El
.Sh FILES
.Bl -tag -width /etc/rvnd?? -compact
.It Pa /dev/{,r}{,s}vnd*
.El
.Sh EXAMPLES
Configure a CD-ROM or DVD image file as vnode disk svnd0
and mount the ISO 9660 file system contained in it:
.Bd -literal -offset indent
# vnconfig svnd0 /tmp/diskimage
# mount -t cd9660 /dev/svnd0c /mnt
.Ed
.Pp
Configure an encrypted image file as vnode disk svnd0 and mount the FFS
file system contained in it.
The encryption key does not echo and must be entered every time
the vnode disk is configured.
.Bd -literal -offset indent
# vnconfig -k svnd0 /tmp/cryptimg
Encryption key:
# mount /dev/svnd0c /mnt
.Ed
.Pp
Same as above, but now configure the vnode using PKCS #5 PBKDF2 and
a salt file with 20000 rounds:
.Bd -literal -offset indent
# vnconfig -K 20000 svnd0 /tmp/cryptimg
Encryption key:
Salt file: /tmp/cryptsalt
# mount /dev/svnd0c /mnt
.Ed
.Pp
Unmount the file system and unconfigure the vnode device:
.Bd -literal -offset indent
# umount /mnt
# vnconfig -u svnd0
.Ed
.Pp
Some possible vnd configurations for
.Pa /etc/fstab
are listed below.
.Pp
For lines with type
.Dq ffs ,
the
.Dq noauto
option must be set to prevent a
.Xr mount 8
of the FFS partitions
before the necessary vnd devices are configured.
Also, the
.Dq fs_passno
field has to be set to 0 to prevent
.Xr fsck 8
from checking the file system for the same reasons.
.Bd -literal -offset indent
/home/img0 /dev/svnd0c vnd rw             0 0
/dev/svnd0a /home/mnt0 ffs rw,noauto,sync 0 0

/home/img1 /dev/svnd1c vnd rw,-k                       0 0
/dev/svnd1a /home/mnt1 ffs rw,sync,noauto,nodev,nosuid 0 0

/home/img2 /dev/svnd2c vnd rw,-K=20000                 0 0
/dev/svnd2a /home/mnt2 ffs rw,sync,noauto,nodev,nosuid 0 0

/home/img3 /dev/svnd3c vnd rw,-K=20000,-S=/home/img3.salt 0 0
/dev/svnd3a /home/mnt3 ffs rw,noauto                      0 0
/dev/svnd3d /home/mnt4 ffs rw,noauto                      0 0
/dev/svnd3e /home/mnt5 ffs rw,noauto                      0 0
.Ed
.Sh SEE ALSO
.Xr vnd 4 ,
.Xr fstab 5 ,
.Xr mount 8 ,
.Xr swapon 8 ,
.Xr umount 8
.Sh HISTORY
The
.Nm
command first appeared in
.Ox 4.2 .
.Sh AUTHORS
.An David Krause .
.Sh BUGS
Checking filesystems within svnd images using
.Xr fsck 8
at boot time, as well as mounting them at that point of time is not yet
possible, because the mount option
.Dq noauto
is still necessary at the moment.