This manual page documents briefly the
This manual page was written for the Debian GNU/Linux distribution
because the original program does not have a manual page.
Instead, there is some documentation available at
which you are encouraged to read
is not a program designed to break the password of every user in
the file. Rather, it is designed to find weak passwords in the file, by
attacking those sorts of bad passwords which are most likely to be used,
in the order in which they would most easily be found (ie: are most
likely to be used by a moronic user).
Crack is not designed to break user passwords; it is designed to break
password files. This is a subtle but important distinction.
will show what passwords have been cracked, as well as view
errors that have been detected in the source password files, etc.
Guesses are listed chronologically, so users who wish to see incremental
changes in the output as Crack continues to run over a course of days or
weeks, are encouraged to wrap invocations of Crack-Reporter in a script with
A summary of options are included below.
Creates and compresses the dictionaries Crack will use
Compiles the binaries for Crack (not necessary for Debian GNU/Linux since
they are already provided)
Lets you see what the Crack script is doing.
Used when restarting an abnormally-terminated run; suppresses rebuild
of the gecos-derived dictionaries.
Runs the password cracker in the foreground, with stdin, stdout and
stderr attached to the usual places.
Specifies the input file format.
Starts password cracking from rule number "N".
Prevents deletion of the temporary file used to store the password
E-Mail a warning message to anyone whose password is cracked.
See the script nastygram.
Runs the password cracker in network mode.
Runs the password cracker at a reduced priority, so that other jobs can
take priority over the CPU.
Internal options used to support networking.
Produces output in a fairly basic HTML-readable format.
Suppresses the reporting of errors in the password file
(corrupt entries, etc)
To run Crack
# Crack -nice 10 /etc/passwd
If a Crack session is killed accidentally, it can be restarted with moderate
efficiency by doing:
However if all you wish to do is start cracking passwords from some specific
rule number, or to restart a run whilst skipping over a few rulesets, try:
Crack [-recover] -from N filename ...
...where N is the number of the rule to start working from.
Location of the Crack program and scripts.
Location for the temporary files used by Crack.
You will find more documentation about Crack in the text files available in
Documentation includes the program's Manual (in HTML and Text files), the
User's Frequently Asked Questions (FAQ), examples, articles and even some
This manual page was written by Javier Fernandez-Sanguino <firstname.lastname@example.org>,
for the Debian GNU/Linux system (but may be used by others).