.\" mcookie.1 --
.\" Public Domain 1995 Rickard E. Faith (faith@cs.unc.edu)
.TH MCOOKIE 1 "June 2011" "util-linux" "User Commands"
.SH NAME
mcookie \- generate magic cookies for xauth
.SH SYNOPSIS
.B mcookie
[\fIoptions\fR]
.SH DESCRIPTION
.B mcookie
generates a 128-bit random hexadecimal number for use with the X authority
system.  Typical usage:
.RS
xauth add :0 . `mcookie`
.RE
.PP
The "random" number generated is actually the output of the MD5 message
digest fed with various pieces of random information: the current time, the
process id, the parent process id, and optionally the contents of an input
file. and several bytes of information from the first of the following
devices which is present:
.IR /dev/random ,
.IR /dev/urandom ,
files in
.IR /proc ,
.IR /dev/audio .
.SH OPTIONS
.TP
\fB\-f\fR, \fB\-\-file\fR=\fIFILE\fR
Use file as a macig cookie seed. When file is defined as `-' character
input is read from stdin.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
Explain what is being done.
.TP
\fB\-V\fR, \fB\-\-version\fR
Output version information and exit.
.TP
\fB\-h\fR, \fB\-\-help\fR
Display this help and exit.
.SH BUGS
The entropy in the generated 128-bit is probably quite small (and,
therefore, vulnerable to attack) unless a non-pseudorandom number generator
is used (e.g.,
.I /dev/random
under Linux).
.PP
It is assumed that none of the devices opened will block.
.SH FILES
.I /dev/random
.br
.I /dev/urandom
.br
.I /dev/audio
.br
.I /proc/stat
.br
.I /proc/loadavg
.SH "SEE ALSO"
.BR X (1),
.BR xauth (1),
.BR md5sum (1)
.SH AVAILABILITY
The mcookie command is part of the util-linux package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux/.