update-cracklib

update-cracklib [options] dictionary1 dictionary2 ...

-v
    Verbose mode. Displays additional information during the database creation process.

-q
    Quiet mode. Suppresses most output.

-d directory
    Specify the directory to store the generated dictionary files. If not specified, the default directory configured in /etc/cracklib/cracklib.conf will be used.

The update-cracklib command is used to generate the CrackLib password dictionary databases. CrackLib is a library that can be used to test whether a potential password is easily guessable (and therefore insecure). The update-cracklib command takes a list of files, usually word lists, and processes them to create the databases used by CrackLib. These databases are essentially frequency tables of words and patterns that are considered common, allowing CrackLib to efficiently identify weak passwords.
This command is crucial for system security, as it helps prevent users from choosing passwords that can be easily cracked using dictionary attacks. It typically runs as part of system maintenance to update the password dictionaries when new word lists or other relevant data become available. The utility reads its configuration from /etc/cracklib/cracklib.conf. The typical directory for the generated password files is /var/cache/cracklib/cracklib_dict.pwd/

update-cracklib usually requires root privileges to write to the dictionary directories. The performance and effectiveness of CrackLib are directly tied to the quality and comprehensiveness of the wordlists used to generate the databases. Regularly updating these lists is critical to maintaining password security.

The /etc/cracklib/cracklib.conf file contains configuration options for update-cracklib, including the default dictionary directory.

CrackLib was developed to provide a way to prevent users from selecting easily guessable passwords. The update-cracklib utility is an integral part of the CrackLib system, responsible for creating and updating the databases that CrackLib uses. Over time, as new password cracking techniques and common word lists have emerged, the update-cracklib command has been used to incorporate these into the CrackLib databases, ensuring its continued effectiveness.

cracklib(3), passwd(1)