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

AVAILABILITY

The mcookie command is part of the util-linux package which can be downloaded from