.\" mcookie.1 --
.\" Public Domain 1995 Rickard E. Faith (faith@cs.unc.edu)
.TH MCOOKIE 1 "December 2014" "util-linux" "User Commands"
.SH NAME
mcookie \- generate magic cookies for xauth
.SH SYNOPSIS
.B mcookie
[options]
.SH DESCRIPTION
.B mcookie
generates a 128-bit random hexadecimal number for use with the X authority
system.  Typical usage:
.sp
.RS
.B xauth add :0 . `mcookie`
.RE
.PP
The "random" number generated is actually the MD5 message
digest of random information coming from one of the sources
.IR getrandom ()
system call,
.IR /dev/urandom ,
.IR /dev/random ,
or the
.IR "libc pseudo-random functions" ,
in this preference order. See also the option \fB\-\-file\fR.
.SH OPTIONS
.TP
.BR \-f , " \-\-file " \fIfile
Use this \fIfile\fR as an additional source of randomness (for example /dev/urandom).
When \fIfile\fR is '-', characters are read from standard input.
.TP
.BR \-m , " \-\-max\-size " \fInumber
Read from \fIfile\fR only this \fInumber\fR of bytes.
This option is meant to be used when reading additional
randomness from a file or device.
.IP
The
.I number
argument may be followed by the multiplicative suffixes KiB=1024,
MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is
optional, e.g., "K" has the same meaning as "KiB") or the suffixes
KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB.
.TP
.BR \-v , " \-\-verbose"
Inform where randomness originated, with amount of entropy read from each
source.
.TP
.BR \-V , " \-\-version"
Display version information and exit.
.TP
.BR \-h , " \-\-help"
Display help text and exit.
.SH BUGS
It is assumed that none of the randomness sources will block.
.SH FILES
.I /dev/urandom
.br
.I /dev/random
.SH "SEE ALSO"
.BR md5sum (1),
.BR X (1),
.BR xauth (1),
.BR rand (3)
.SH AVAILABILITY
The mcookie command is part of the util-linux package and is available from
.UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
Linux Kernel Archive
.UE .