En distribuciones como Ubuntu se puede instalar desde el gestor de paquetes Synaptic.

nir@nir-desktop:~/Escritorio$ john

John the Ripper password cracker, version 1.7.3.1
Copyright (c) 1996-2008 by Solar Designer and others

Homepage: http://www.openwall.com/john/

Usage: john [OPTIONS] [PASSWORD-FILES]
--single                   "single crack" mode
--wordlist=FILE --stdin    wordlist mode, read words from FILE or stdin
--rules                    enable word mangling rules for wordlist mode
--incremental[=MODE]       "incremental" mode [using section MODE]
--external=MODE            external mode or word filter
--stdout[=LENGTH]          just output candidate passwords [cut at LENGTH]
--restore[=NAME]           restore an interrupted session [called NAME]
--session=NAME             give a new session the NAME
--status[=NAME]            print status of a session [called NAME]
--make-charset=FILE        make a charset, FILE will be overwritten
--show                     show cracked passwords
--test                     perform a benchmark
--users=[-]LOGIN|UID[,..]  [do not] load this (these) user(s) only
--groups=[-]GID[,..]       load users [not] of this (these) group(s) only
--shells=[-]SHELL[,..]     load users with[out] this (these) shell(s) only
--salts=[-]COUNT           load salts with[out] at least COUNT passwords only
--format=NAME              force hash type NAME: DES/BSDI/MD5/BF/AFS/LM/NT/mscash/NETLM/NETNTLM/bfegg/DOMINOSEC/lotus5/raw-MD5/raw-sha1/IPB2/nsldap/openssha/HDAA
--save-memory=LEVEL        enable memory saving, at LEVEL 1..3

P.D.: Mejor añade al título de este post/tema que va sobre JOHN THE RIPPER password cracker.

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