mcookie (1)

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 output of the MD5 message digest fed with random information from one of the sources /dev/urandom, /dev/random, or libc pseudo-random functions in this preference order.

-f, --file=FILE

Use additional file as a macig cookie random seed. When file is defined as '-' character input is read from stdin.

-m, --max-size=number

Read form FILE only number of bytes. This option is meant to be used when reading additional randomness from a 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.

-V, --version

Display version information and exit.

-h, --help

Display help text and exit.

It is assumed that none of the randomness sources will block.

/dev/urandom

/dev/random

X(1), xauth(1), md5sum(1), rand(3)

The mcookie command is part of the util-linux package and is available from

Linux Kernel Archive