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 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.

-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/).