Provided by:
passwd_4.1.1-1ubuntu1_i386 
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.
-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).