mcookie − generate magic cookies for xauth
mcookie [options]
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.
−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.
/dev/urandom
/dev/random
It is assumed that none of the randomness sources will block.
md5sum(1), X(7), xauth(1), rand(3)
For bug reports, use the issue tracker at <https://github.com/util−linux/util−linux/issues>.
The mcookie command is part of the util−linux package which can be downloaded from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils/util−linux/>.