Provided by: passwd_4.8.1-2ubuntu2.2_amd64 
NOME
useradd - crea un nuovo utente o aggiorna le informazioni predefinite per i nuovi utenti
SINOSSI
useradd [opzioni] LOGIN
useradd -D
useradd -D [opzioni]
DESCRIZIONE
useradd is a low level utility for adding users. On Debian, administrators should usually use adduser(8) instead. When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line plus the default values from the system. Depending on command line options, the useradd command will update system files and may also create the new user's home directory and copy initial files. 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. The directory
HOME_DIR does not have to exist but will not be created if it is missing.
-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.
For the compatibility with previous Debian's useradd, the -O option is also supported.
-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.
-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.
It is usually recommended to only use usernames that begin with a lower case letter or an underscore,
followed by lower case letters, digits, underscores, or dashes. They can end with a dollar sign. In
regular expression terms: [a-z_][a-z0-9_-]*[$]?
On Debian, the only constraints are that usernames must neither start with a dash ('-') nor plus ('+')
nor tilde ('~') nor contain a colon (':'), a comma (','), or a whitespace (space: ' ', end of line: '\n',
tabulation: '\t', etc.). Note that using a slash ('/') may break the default algorithm for the definition
of the user's home directory.
On Ubuntu, the same constraints as Debian are in place, with the additional constraint that the username
cannot be fully numeric. This includes octal and hexadecimal syntax.
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:
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).