Provided by: passwd_4.1.1-6ubuntu6_i386 bug

NOME

       chpasswd - aggiorna le password in modo non interattivo

SINOSSI

       chpasswd [opzioni]

DESCRIZIONE

       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:

       nome_utente:password

       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.

       Questo comando è appositamente pensato per grossi sistemi in cui si
       abbia la necessità di creare molti account nello stesso momento.

OPZIONI

       Il comando chpasswd accetta le seguenti opzioni:

       -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
           Le password fornite sono in forma cifrata.

       -S, --stdout
           Report encrypted passwords to stdout instead of updating password
           file.

       -h, --help
           Mostra un messaggio di aiuto ed esce.

       -m, --md5
           Usa la cifratura MD5 anziché DES quando le password fornite non
           sono cifrate.

       -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.

AVVISI/CAVEAT

       Remember to set permissions or umask to prevent readability of
       unencrypted files by other users.

       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.

CONFIGURATION

       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

               Note: this parameter overrides the MD5_CRYPT_ENAB variable.

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

       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.

FILE

       /etc/passwd
           informazioni sugli account utente.

       /etc/shadow
           Informazioni sicure sugli account di utenti.

       /etc/login.defs
           Shadow password suite configuration.

VEDERE ANCHE

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