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 in- put. -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 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 <https://github.com/util-linux/util-linux/issues>. AVAILABILITY The mcookie command is part of the util-linux package which can be down- loaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util-linux/>. util-linux 2.41.2 2025-09-22 MCOOKIE(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | BUGS | SEE ALSO | REPORTING BUGS | AVAILABILITY
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