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Langue: en

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Version: 25 September 1995 (ubuntu - 24/10/10)

Section: 1 (Commandes utilisateur)


mcookie - generate magic cookies for xauth


mcookie [-v] [-f filename]


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 output of the MD5 message digest fed with various pieces of random information: the current time, the process id, the parent process id, the contents of an input file (if -f is specified), and several bytes of information from the first of the following devices which is present: /dev/random, /dev/urandom, files in /proc, /dev/audio.


The entropy in the generated 128-bit is probably quite small (and, therefore, vulnerable to attack) unless a non-pseudorandom number generator is used (e.g., /dev/random under Linux).

It is assumed that none of the devices opened will block.




X(1), xauth(1), md5sum(1)


The mcookie command is part of the util-linux-ng package and is available from
Choisir sa vie, c'est décider à l'avance et
volontairement ce qui vous empêchera de dormir.
-+- Gilbert Cesbron (1913-1979), de petites choses. -+-