OpenBSD-4.6/sbin/fsirand/fsirand.8

.\" $OpenBSD: fsirand.8,v 1.29 2007/05/31 19:19:44 jmc Exp $
.\"
.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
.\"
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.Dd $Mdocdate: May 31 2007 $
.Dt FSIRAND 8
.Os
.Sh NAME
.Nm fsirand
.Nd randomize inode generation numbers
.Sh SYNOPSIS
.Nm fsirand
.Op Fl bfp
.Ar special ...
.Sh DESCRIPTION
The
.Nm
command installs random generation numbers on all the inodes for
each filesystem specified on the command line by
.Ar special .
This increases the security of NFS-exported filesystems by making
it difficult to
.Dq guess
filehandles.
.Pp
.Em Note :
.Xr newfs 8
now does the equivalent of
.Nm
itself so it is no longer necessary to
run
.Nm
by hand on a new filesystem.
It is only used to re-randomize or report on an existing filesystem.
.Pp
.Nm
should only be used on an unmounted filesystem that
has been checked with
.Xr fsck 8
or a filesystem that is mounted read-only.
.Nm
may be used on the root filesystem in single-user mode
but the system should be rebooted via
.Dq reboot -n
afterwards.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl b
Use the default block size (usually 512 bytes) instead
of the value gleaned from the disklabel.
.It Fl f
Force
.Nm
to run even if the filesystem on
.Ar special
is not marked as clean.
.It Fl p
Print the current generation numbers for all inodes instead of
generating new ones.
.El
.Sh SEE ALSO
.Xr fs 5 ,
.Xr fsck 8 ,
.Xr newfs 8 ,
.Xr reboot 8
.Sh HISTORY
The
.Nm
command appeared in SunOS 3.x.
This version of
.Nm
first appeared in
.Ox 2.1 .
.Sh AUTHORS
.An Todd C. Miller
.Sh CAVEATS
Since
.Nm
allocates enough memory to hold all the inodes in
a given cylinder group, it may use a large amount
of memory for large disks with few cylinder groups.