USERADD

By default, a group will also be created for the new user (see -g, -N, -U, and USERGROUPS_ENAB).  

OPZIONI

The options which apply to the useradd command are:

--badname 

Allow names that do not conform to standards.

-b, --base-dir BASE_DIR

The default base directory for the system if -d HOME_DIR is not specified. BASE_DIR is concatenated with the account name to define the home directory. If the -m option is not used, BASE_DIR must exist.

If this option is not specified, useradd will use the base directory specified by the HOME variable in /etc/default/useradd, or /home by default.

-c, --comment COMMENT

Un testo qualsiasi. Di norma è una breve descrizione del login, ed è attualmente usato come nome completo dell'utente.

-d, --home-dir HOME_DIR

The new user will be created using HOME_DIR as the value for the user's login directory. The default is to append the LOGIN name to BASE_DIR and use that as the login directory name. If the directory HOME_DIR does not exist, then it will be created unless the -M option is specified.

-D, --defaults

Vedere oltre, la sezione «Cambiare i valori predefiniti».

-e, --expiredate EXPIRE_DATE

The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD.

If not specified, useradd will use the default expiry date specified by the EXPIRE variable in /etc/default/useradd, or an empty string (no expiry) by default.

-f, --inactive INACTIVE

Il numero di giorni dopo la scadenza della password prima che l'account venga permanentemente disabilitato. Un valore pari a 0 disabilita l'account non appena la password è scaduta, ed un valore pari a -1 disabilita questa funzionalità.

If not specified, useradd will use the default inactivity period specified by the INACTIVE variable in /etc/default/useradd, or -1 by default.

-g, --gid GROUP

Il nome o numero del gruppo di connessione iniziale dell'utente. Il nome del gruppo deve esistere. Un numero di gruppo deve riferirsi ad un gruppo già esistente.

If not specified, the behavior of useradd will depend on the USERGROUPS_ENAB variable in /etc/login.defs. If this variable is set to yes (or -U/--user-group is specified on the command line), a group will be created for the user, with the same name as her loginname. If the variable is set to no (or -N/--no-user-group is specified on the command line), useradd will set the primary group of the new user to the value specified by the GROUP variable in /etc/default/useradd, or 100 by default.

-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]

A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option. The default is for the user to belong only to the initial group.

-h, --help

Mostra un messaggio di aiuto ed esce.

-k, --skel SKEL_DIR

The skeleton directory, which contains files and directories to be copied in the user's home directory, when the home directory is created by useradd.

This option is only valid if the -m (or --create-home) option is specified.

If this option is not set, the skeleton directory is defined by the SKEL variable in /etc/default/useradd or, by default, /etc/skel.

Se possibile vengono copiate le ACL e gli attributi estesi.

-K, --key KEY=VALUE

Overrides /etc/login.defs defaults (UID_MIN, UID_MAX, UMASK, PASS_MAX_DAYS and others).

Example: -K PASS_MAX_DAYS=-1 can be used when creating system account to turn off password aging, even though system account has no password at all. Multiple -K options can be specified, e.g.: -K UID_MIN=100  -K UID_MAX=499

-l, --no-log-init

Non aggiunge l'utente ai database «lastlog» e «faillog».

By default, the user's entries in the lastlog and faillog databases are reset to avoid reusing the entry from a previously deleted user.

-m, --create-home

Create the user's home directory if it does not exist. The files and directories contained in the skeleton directory (which can be defined with the -k option) will be copied to the home directory.

By default, if this option is not specified and CREATE_HOME is not enabled, no home directories are created.

The directory where the user's home directory is created must exist and have proper SELinux context and permissions. Otherwise the user's home directory cannot be created or accessed.

-M, --no-create-home

Do no create the user's home directory, even if the system wide setting from /etc/login.defs (CREATE_HOME) is set to yes.

-N, --no-user-group

Do not create a group with the same name as the user, but add the user to the group specified by the -g option or by the GROUP variable in /etc/default/useradd.

The default behavior (if the -g, -N, and -U options are not specified) is defined by the USERGROUPS_ENAB variable in /etc/login.defs.

-o, --non-unique

Permette la creazione di un utente con un UID duplicato (non unico).

This option is only valid in combination with the -u option.

-p, --password PASSWORD

The encrypted password, as returned by crypt(3). The default is to disable the password.

Note: This option is not recommended because the password (or encrypted password) will be visible by users listing the processes.

Ci si deve accertare che la password rispetti le norme delle password del sistema.

-r, --system

Crea un account di sistema.

System users will be created with no aging information in /etc/shadow, and their numeric identifiers are chosen in the SYS_UID_MIN-SYS_UID_MAX range, defined in /etc/login.defs, instead of UID_MIN-UID_MAX (and their GID counterparts for the creation of groups).

Note that useradd will not create a home directory for such a user, regardless of the default setting in /etc/login.defs (CREATE_HOME). You have to specify the -m options if you want a home directory for a system account to be created.

-R, --root CHROOT_DIR

Apply changes in the CHROOT_DIR directory and use the configuration files from the CHROOT_DIR directory.

-P, --prefix PREFIX_DIR

Apply changes in the PREFIX_DIR directory and use the configuration files from the PREFIX_DIR directory. This option does not chroot and is intended for preparing a cross-compilation target. Some limitations: NIS and LDAP users/groups are not verified. PAM authentication is using the host files. No SELINUX support.

-s, --shell SHELL

The name of the user's login shell. The default is to leave this field blank, which causes the system to select the default login shell specified by the SHELL variable in /etc/default/useradd, or an empty string by default.

-u, --uid UID

The numerical value of the user's ID. This value must be unique, unless the -o option is used. The value must be non-negative. The default is to use the smallest ID value greater than or equal to UID_MIN and greater than every other user.

See also the -r option and the UID_MAX description.

-U, --user-group

Crea un gruppo con lo stesso nome dell'utente e aggiunge l'utente al gruppo stesso.

The default behavior (if the -g, -N, and -U options are not specified) is defined by the USERGROUPS_ENAB variable in /etc/login.defs.

-Z, --selinux-user SEUSER

L'utente SELinux per questo login utente. Lasciando questo campo vuoto si fa in modo che il sistema selezioni automaticamente l'utente SELinux.

Cambiare i valori predefiniti

When invoked with only the -D option, useradd will display the current default values. When invoked with -D plus other options, useradd will update the default values for the specified options. Valid default-changing options are:

-b, --base-dir BASE_DIR

The path prefix for a new user's home directory. The user's name will be affixed to the end of BASE_DIR to form the new user's home directory name, if the -d option is not used when creating a new account.

This option sets the HOME variable in /etc/default/useradd.

-e, --expiredate EXPIRE_DATE

La data in cui l'account dell'utente verrà disabilitato.

This option sets the EXPIRE variable in /etc/default/useradd.

-f, --inactive INACTIVE

Il numero di giorni dopo la scadenza di una password prima che l'account venga disabilitato.

This option sets the INACTIVE variable in /etc/default/useradd.

-g, --gid GROUP

The group name or ID for a new user's initial group (when the -N/--no-user-group is used or when the USERGROUPS_ENAB variable is set to no in /etc/login.defs). The named group must exist, and a numerical group ID must have an existing entry.

This option sets the GROUP variable in /etc/default/useradd.

-s, --shell SHELL

Il nome della shell di login per il nuovo utente.

This option sets the SHELL variable in /etc/default/useradd.

NOTE

The system administrator is responsible for placing the default user files in the /etc/skel/ directory (or any other skeleton directory specified in /etc/default/useradd or on the command line).  

AVVISI/CAVEAT

Non è possibile aggiungere un utente ad un gruppo NIS o LDAP. Questo deve essere fatto sul server corrispondente.

Similarly, if the username already exists in an external user database such as NIS or LDAP, useradd will deny the user account creation request.

Usernames may contain only lower and upper case letters, digits, underscores, or dashes. They can end with a dollar sign. Dashes are not allowed at the beginning of the username. Fully numeric usernames and usernames . or .. are also disallowed. It is not recommended to use usernames beginning with . character as their home directories will be hidden in the ls output.

I nomi utente non possono eccedere i 32 caratteri di lunghezza.  

CONFIGURAZIONE

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

CREATE_HOME (boolean)

Indica se per i nuovi utenti va creata la directory home.

Questa impostazione non viene applicata agli utenti di sistema e può essere modificata sulla riga di comando.

GID_MAX (number), GID_MIN (number)

Range of group IDs used for the creation of regular groups by useradd, groupadd, or newusers.

The default value for GID_MIN (resp. GID_MAX) is 1000 (resp. 60000).

HOME_MODE (number)

The mode for new home directories. If not specified, the UMASK is used to create the mode.

useradd and newusers use this to set the mode of the home directory they create.

LASTLOG_UID_MAX (number)

Highest user ID number for which the lastlog entries should be updated. As higher user IDs are usually tracked by remote user identity and authentication services there is no need to create a huge sparse lastlog file for them.

No LASTLOG_UID_MAX option present in the configuration means that there is no user ID limit for writing lastlog entries.

MAIL_DIR (string)

La directory di spool per la posta. Questa è necessaria per manipolare la casella di posta quando il corrispondente account utente viene modificato o cancellato. Se non è specificata viene utilizzato un valore impostato al momento della compilazione.

MAIL_FILE (string)

Imposta la posizione delle caselle di posta degli utenti relative alla loro directory home.

The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and userdel to create, move, or delete the user's mail spool.

If MAIL_CHECK_ENAB is set to yes, they are also used to define the MAIL environment variable.

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.

PASS_MAX_DAYS (number)

Il numero massimo di giorni che una password può essere utilizzata. Se la password è più vecchia verrà imposto il suo cambiamento. Se non specificato viene assunto -1 (che disabilita questo controllo).

PASS_MIN_DAYS (number)

Il numero minimo di giorni tra due cambiamenti di password. Ogni tentativo di cambiare la password prima di questo periodo verrà rifiutato. Se non specificato viene assunto -1 (che disabilita questo controllo).

PASS_WARN_AGE (number)

Il numero di giorni per i quali un utente va avvisato che la sua password sta per scadere. Se zero l'utente viene avvisato solo alla scadenza. Un valore negativo indica che non si deve avvisare mai. Se non specificato allora non c'è nessun avviso.

SUB_GID_MIN (number), SUB_GID_MAX (number), SUB_GID_COUNT (number)

If /etc/subuid exists, the commands useradd and newusers (unless the user already have subordinate group IDs) allocate SUB_GID_COUNT unused group IDs from the range SUB_GID_MIN to SUB_GID_MAX for each new user.

The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are respectively 100000, 600100000 and 65536.

SUB_UID_MIN (number), SUB_UID_MAX (number), SUB_UID_COUNT (number)

If /etc/subuid exists, the commands useradd and newusers (unless the user already have subordinate user IDs) allocate SUB_UID_COUNT unused user IDs from the range SUB_UID_MIN to SUB_UID_MAX for each new user.

The default values for SUB_UID_MIN, SUB_UID_MAX, SUB_UID_COUNT are respectively 100000, 600100000 and 65536.

SYS_GID_MAX (number), SYS_GID_MIN (number)

Range of group IDs used for the creation of system groups by useradd, groupadd, or newusers.

The default value for SYS_GID_MIN (resp. SYS_GID_MAX) is 101 (resp. GID_MIN-1).

SYS_UID_MAX (number), SYS_UID_MIN (number)

Range of user IDs used for the creation of system users by useradd or newusers.

The default value for SYS_UID_MIN (resp. SYS_UID_MAX) is 101 (resp. UID_MIN-1).

UID_MAX (number), UID_MIN (number)

Range of user IDs used for the creation of regular users by useradd or newusers.

The default value for UID_MIN (resp. UID_MAX) is 1000 (resp. 60000).

UMASK (number)

La maschera di permessi alla creazione dei file è inizializzata con questo valore. Se non specificato la maschera viene impostata a 022.

useradd and newusers use this mask to set the mode of the home directory they create if HOME_MODE is not set.

It is also used by login to define users' initial umask. Note that this mask can be overridden by the user's GECOS line (if QUOTAS_ENAB is set) or by the specification of a limit with the K identifier in limits(5).

USERGROUPS_ENAB (boolean)

Abilita l'impostazione dei bit di gruppo di umask in modo che siano gli stessi dei bit del proprietario (esempio: 022 -> 002, 077 -> 007) per utenti non root a condizione che uid e gid siano identici e che il nome utente sia lo stesso del gruppo primario.

If set to yes, userdel will remove the user's group if it contains no more members, and useradd will create by default a group with the name of the user.

FILE

/etc/passwd

Informazioni sugli account utente.

/etc/shadow

Informazioni sicure sugli account utente.

/etc/group

Informazioni sugli account di gruppo.

/etc/gshadow

Informazioni sicure sugli account di gruppo.

/etc/default/useradd

Valori predefiniti per la creazione dell'account.

/etc/skel/

Directory contenente i file predefiniti.

/etc/subgid

Per user subordinate group IDs.

/etc/subuid

Per user subordinate user IDs.

/etc/login.defs

Configurazione del pacchetto password shadow

VALORI RESTITUITI

The useradd command exits with the following values:

0

success

1

can't update password file

2

invalid command syntax

3

invalid argument to option

4

UID already in use (and no -o)

6

specified group doesn't exist

9

username already in use

10

can't update group file

12

can't create home directory

14

can't update SELinux user mapping

VEDERE ANCHE

chfn(1), chsh(1), passwd(1), crypt(3), groupadd(8), groupdel(8), groupmod(8), login.defs(5), newusers(8), subgid(5), subuid(5), userdel(8), usermod(8).