mcookie

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(1), 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)