mcookie(1) — Linux manual page
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(2)
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 standard 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 device.
The 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.
-v, --verbose
Inform where randomness originated, with amount of entropy
read from each source.
-h, --help
Display help text and exit.
-V, --version
Print version and exit.
FILES
/dev/urandom
/dev/random
BUGS
It is assumed that none of the randomness sources will block.
SEE ALSO
md5sum(1), X(7), xauth(1), rand(3)
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
AVAILABILITY
The mcookie command is part of the util-linux package which can
be downloaded from Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>. This page
is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have
a bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-10.) If you discover
any rendering problems in this HTML version of the page, or you
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