MCOOKIE(1) User Commands MCOOKIE(1)
NAME
mcookie - generate magic cookies for xauth
SYNOPSIS
mcookie [options]
DESCRIPTION
mcookie generates a 128-bit random hexadecimal number for use with the
X authority system. Typical usage:
xauth add :0 . `mcookie`
The "random" number generated is actually the MD5 message digest of
random information coming from one of the sources getrandom() system
call, /dev/urandom, /dev/random, or the libc pseudo-random functions,
in this preference order. See also the option --file.
OPTIONS
-f, --file file
Use this file as an additional source of randomness (for example
/dev/urandom). When file is '-', characters are read from stan-
dard input.
-m, --max-size number
Read from file only this number of bytes. This option is meant
to be used when reading additional randomness from a file or de-
vice.
The number argument may be followed by the multiplicative suf-
fixes 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 mean-
ing as "KiB") or the suffixes KB=1000, MB=1000*1000, and so on
for GB, TB, PB, EB, ZB and YB.
-v, --verbose
Inform where randomness originated, with amount of entropy read
from each source.
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
BUGS
It is assumed that none of the randomness sources will block.
FILES
/dev/urandom
/dev/random
SEE ALSO
md5sum(1), X(7), xauth(1), rand(3)
AVAILABILITY
The mcookie command is part of the util-linux package and is available
from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-
linux/>.
util-linux December 2014 MCOOKIE(1)