chpasswd − Mettre à jour des mots de passe par lot

chpasswd [options]

The chpasswd command reads a list of user name and password pairs from standard input and uses this information to update a group of existing users. Each line is of the format:

nom_utilisateur:mot_de_passe

By default the supplied password must be in clear−text, and is encrypted by chpasswd. Also the password age will be updated, if present.

The default encryption algorithm can be defined for the system with the ENCRYPT_METHOD variable of /etc/login.defs, and can be overwiten with the −e, −m, or −c options.

Cette commande est destinée aux gros systèmes pour lesquels un nombre importants de comptes sont créés en une seule fois.

Les options disponibles pour la commande chpasswd sont :

−c, −−crypt−method

Use the specified method to encrypt the passwords.

The available methods are DES, MD5, NONE, and SHA256 or SHA512 if your libc support these methods.

−e, −−encrypted

Indique que les mots de passe fournis sont chiffrés.

−S, −−stdout

Report encrypted passwords to stdout instead of updating password file.

−h, −−help

Afficher un message d´aide et quitter.

−m, −−md5

Permettre d´utiliser le chiffrement MD5, plutôt que DES, lorsque les mots de passe fournis ne sont pas chiffrés.

−s, −−sha−rounds

Use the specified number of rounds to encrypt the passwords.

The value 0 means that the system will choose the default number of rounds for the crypt method (5000).

A minimal value of 1000 and a maximal value of 999,999,999 will be enforced.

You can only use this option with the SHA256 or SHA512 crypt method.

By default, the number of rounds is defined by the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in /etc/login.defs.

Pensez à fixer les permissions ou umask afin d´empêcher la lecture par les autres utilisateurs des fichiers non chiffrés.

PAM is not used to update the passwords. Only /etc/passwd and /etc/shadow are updated, and the various checks or options provided by PAM modules are not used.

The following configuration variables in /etc/login.defs change the behavior of this tool:

ENCRYPT_METHOD (string)

This defines the system default encryption algorithm for encrypting passwords (if no algorithm are specified on the command line).

It can take one of these values:

• DES (default)

• MD5

• SHA256

• SHA512

MD5_CRYPT_ENAB (boolean)

Indicate if passwords must be encrypted using the MD5−based algorithm. If set to yes, new passwords will be encrypted using the MD5−based algorithm compatible with the one used by recent releases of FreeBSD. It supports passwords of unlimited length and longer salt strings. Set to no if you need to copy encrypted passwords to other systems which don´t understand the new algorithm. Default is no.

This variable is superceded by the ENCRYPT_METHOD variable or by any command line option used to configure the encryption algorithm.

This variable is deprecated. You should use ENCRYPT_METHOD.

Note: if you use PAM, it is recommended to set this variable consistently with the PAM modules configuration.

SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)

When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines the number of SHA rounds used by the encryption algorithm by default (when the number of rounds is not specified on the command line).

With a lot of rounds, it is more difficult to brute forcing the password. But note also that more CPU resources will be needed to authenticate users.

If not specified, the libc will choose the default number of rounds (5000).

The values must be inside the 1000−999999999 range.

If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS values is set, then this value will be used.

If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest value will be used.

/etc/passwd

Informations sur les comptes des utilisateurs.

/etc/shadow

Informations sécurisées sur les comptes utilisateurs.

/etc/login.defs

Configuration de la suite des mots de passe cachés « shadow password ».

passwd(1), newusers(8), useradd(8), login.defs(5).