mcookie(1)

Usage

mcookie [options]

Overview

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: Display version and exit.

Files

/dev/urandom

/dev/random

Releases

18 releases since Debian 1.2 (Rex); the text changed 12 times.

--file since Debian 7 (Wheezy); --help since Debian 7 (Wheezy); --max-size since Debian 8 (Jessie); --verbose since Debian 7 (Wheezy); --version since Debian 7 (Wheezy); -V since Debian 7 (Wheezy); -f since Debian 7 (Wheezy); -h since Debian 7 (Wheezy); -m since Debian 8 (Jessie); -v since Debian 7 (Wheezy).