CHGPASSWD(8)

NOME
chgpasswd - aggiorna le password di gruppo in modalità non interattiva

SINOSSI

chgpasswd [options]

DESCRIZIONE

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

group_name:password

By default the supplied password must be in clear-text, and is encrypted by chgpasswd.

The default encryption algorithm can be defined for the system with the ENCRYPT_METHOD variable of /etc/login.defs, and can be overwritten with the -e 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

The options which apply to the chgpasswd command are:

-c, --crypt-method
    Utilizza il metodo specificato per cifrare le password.

    The available methods are SHA256, SHA512, YESCRYPT and NONE if your libc supports these methods.

-e, --encrypted
    Le password fornite sono in forma cifrata.

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

-R, --root CHROOT_DIR
    Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory. Only absolute paths are supported. No SELINUX support.

-s, --sha-rounds
    Usa il numero specificato di cicli per cifrare la password.

    You can only use this option with crypt method: SHA256 SHA512 YESCRYPT

    By default, the number of rounds for SHA256 or SHA512 is defined by the SHA_CRYPT_MIN_ROUNDS and SHA_CRYPT_MAX_ROUNDS variables in /etc/login.defs.

    A minimal value of 1000 and a maximal value of 999,999,999 will be enforced for SHA256 and SHA512. The default number of rounds is 5000.

    By default, the number of rounds for YESCRYPT is defined by the YESCRYPT_COST_FACTOR in /etc/login.defs.

    A minimal value of 1 and a maximal value of 11 will be enforced for YESCRYPT. The default number of rounds is 5.

AVVISI/CAVEAT

Ricordarsi di impostare i permessi o umask in modo da prevenire la lettura in chiaro da parte di altri utenti.

Ci si deve accertare che le password e il metodo di cifratura rispettino le norme delle password del sistema.

CONFIGURAZIONE

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 is specified on the command line).

    It can take one of these values: SHA256, SHA512 (default), YESCRYPT. See crypt(5) for recommendations.

    Note: this only affects the generation of group passwords. The generation of user passwords is done by PAM and subject to the PAM configuration. It is recommended to set this variable consistently with the PAM configuration.

    History: This variable is used by other programs, which may still default to unsafe algorithms such as DES. To avoid using unsafe algorithms, the variable should always be specified.

MAX_MEMBERS_PER_GROUP (number)
    Maximum members per group entry. When the maximum is reached, a new group entry (line) is started in /etc/group (with the same name, same password, and same GID).

    Il valore predefinito è 0, che non pone nessun limite al numero di membri per gruppo.

    Questa opzione (dividi gruppo) permette di limitare la lunghezza delle righe nel file «group». Questo è utile per essere certi che le righe per gruppi NIS non eccedano i 1024 caratteri.

    Se si deve impostare questo limite, si può usare 25.

    Nota: la divisione dei gruppi potrebbe non essere supportata da ogni strumento (anche all'interno del pacchetto Shadow). Non si dovrebbe utilizzare questa variabile a meno di esserci forzati.

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 force 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), which is orders of magnitude too low for modern hardware.

    Il valore deve essere compreso tra 1.000 e 999.999.999.

    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.

    Note: this only affect the generation of group passwords. The generation of user passwords is done by PAM and subject to the PAM configuration. It is recommended to set this variable consistently with the PAM configuration.

YESCRYPT_COST_FACTOR (number)
    When ENCRYPT_METHOD is set to YESCRYPT, this defines the cost factor used by the encryption algorithm by default (when the cost factor is not specified on the command line).

    With a high cost factor, it is more difficult to brute force the password. But note also that more CPU resources will be needed to authenticate users.

    The value must be inside the 1-11 range.

    Note: this only affect the generation of group passwords. The generation of user passwords is done by PAM and subject to the PAM configuration. It is recommended to set this variable consistently with the PAM configuration.

FILE

/etc/group
    Informazioni sugli account di gruppo.

/etc/gshadow
    Informazioni sicure sugli account di gruppo.

/etc/login.defs
    Configurazione del pacchetto password shadow

VEDERE ANCHE

gpasswd(1), groupadd(8), login.defs(5).