| NEWUSERS(8) | System Management Commands | NEWUSERS(8) |
NOME
newusers - aggiorna e crea nuovi utenti in blocco
SINOSSI
newusers [options] [file]
DESCRIZIONE
The newusers command reads a file (or the standard input by default) and uses this information to update a set of existing users or to create new users. Each line is in the same format as the standard password file (see passwd(5)) with the exceptions explained below:
pw_name:pw_passwd:pw_uid:pw_gid:pw_gecos:pw_dir:pw_shell
pw_name
It can be the name of a new user or the name of an existing user (or a user created before by newusers). In case of an existing user, the user's information will be changed, otherwise a new user will be created.
pw_passwd
pw_uid
If the field is empty, a new (unused) UID will be defined automatically by newusers.
Se questo campo contiene un numero, verrà utilizzato come UID.
If this field contains the name of an existing user (or the name of a user created before by newusers), the UID of the specified user will be used.
Se viene cambiato l'UID di un utente esistente, la proprietà dei file di proprietà dell'utente stesso andrà cambiata manualmente.
pw_gid
If this field contains the name of an existing group (or a group created before by newusers), the GID of this group will be used as the primary group ID for the user.
Se questo campo è numerico, questo numero verrà utilizzato come ID del gruppo primario dell'utente. Se non esiste nessun gruppo con quel GID, ne viene creato uno con il nome dell'utente e il GID specificato.
If this field is empty, a new group will be created with the name of the user and a GID will be automatically defined by newusers to be used as the primary group ID for the user and as the GID for the new group.
If this field contains the name of a group which does not exist (and was not created before by newusers), a new group will be created with the specified name and a GID will be automatically defined by newusers to be used as the primary group ID for the user and GID for the new group.
pw_gecos
pw_dir
If this field does not specify an existing directory, the specified directory is created, with ownership set to the user being created or updated and its primary group. Note that newusers does not create parent directories of the new user's home directory. The newusers command will fail to create the home directory if the parent directories do not exist, and will send a message to stderr informing the user of the failure. The newusers command will not halt or return a failure to the calling shell if it fails to create the home directory, it will continue to process the batch of new users specified.
If the home directory of an existing user is changed, newusers does not move or copy the content of the old directory to the new location. This should be done manually.
pw_shell
newusers first tries to create or change all the specified users, and then write these changes to the user or group databases. If an error occurs (except in the final writes to the databases), no changes are committed to the databases.
Durante il primo passaggio gli utenti vengono creati con la password bloccata (e le password non sono modificate nel caso di utenti che non sono creati). Un secondo passaggio si occupa di aggiornare tutte le password usando PAM. I problemi durante l'aggiornamento delle password sono riportati, ma non interrompono la modifica delle altre password.
Questo comando è appositamente pensato per grossi sistemi nei quali molti account sono aggiornati allo stesso tempo.
OPZIONI
The options which apply to the newusers command are:
--badname
-h, --help
-r, --system
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 login.defs, instead of UID_MIN-UID_MAX (and their GID counterparts for the creation of groups).
-R, --root CHROOT_DIR
AVVISI/CAVEAT
Il file di input deve essere protetto poiché contiene password non cifrate.
CONFIGURAZIONE
The following configuration variables in /etc/login.defs change the behavior of this tool:
GID_MAX (number), GID_MIN (number)
The default value for GID_MIN (resp. GID_MAX) is 1000 (resp. 60000).
HOME_MODE (number)
useradd and newusers use this to set the mode of the home directory they create.
MAX_MEMBERS_PER_GROUP (number)
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)
PASS_WARN_AGE (number)
SUB_GID_MIN (number), SUB_GID_MAX (number), SUB_GID_COUNT (number)
The default values for SUB_GID_MIN, SUB_GID_MAX, SUB_GID_COUNT are respectively 100000, 600100000 and 65536.
SUB_GID_DETERMINISTIC (boolean)
start = SUB_GID_MIN + ((UID - UID_MIN) * SUB_GID_COUNT)
end = start + SUB_GID_COUNT - 1
This ensures the same UID always receives the same subordinate GID range on every system, making it suitable for environments with centralized user management (LDAP, NIS, etc.) or synchronized UIDs across systems.
If SUB_GID_DETERMINISTIC is enabled, you can use usermod --add-subgids -S to produce deterministic subgids.
WARNING: Because UID_MIN is used to calculate the ranges, any change of UID_MIN will change the ranges calculated. SUB_GID_COUNT is used to calculate the ranges, any change of SUB_GID_COUNT will change the ranges calculated. Users with identities less than UID_MIN are incompatible with SUB_GID_DETERMINISTIC, but can still be set manually.
WARNING: Do not mix deterministic and linear (default) allocation on the same system or across systems sharing /etc/subgid via network storage (NFS, etc.). Mixing allocation methods will cause subordinate ID range conflicts and overlaps .
The default value for SUB_GID_DETERMINISTIC is no.
Range Calculation Examples
With default configuration (UID_MIN=1000, SUB_GID_MIN=100000, SUB_GID_COUNT=65536):
| UID | Calculation | Subordinate GID Range |
| 1000 | 100000 + ((1000-1000) * 65536) | 100000-165535 |
| 1001 | 100000 + ((1001-1000) * 65536) | 165536-231071 |
| 1002 | 100000 + ((1002-1000) * 65536) | 231072-296607 |
| 1100 | 100000 + ((1100-1000) * 65536) | 6653600-6719135 |
Subordinate ID Space Planning
When planning subordinate ID allocation, calculate the maximum number of users the space can accommodate:
capacity = (SUB_GID_MAX - SUB_GID_MIN) / SUB_GID_COUNT
With default values: (600100000 - 100000) / 65536 ≈ 9155 users.
For high-density environments with many users and smaller allocations:
SUB_GID_COUNT 4096
SUB_GID_MIN 100000
SUB_GID_MAX 10000000
This gives: (10000000 - 100000) / 4096 ≈ 2417 users.
UNSAFE_SUB_GID_DETERMINISTIC_WRAP (boolean)
Only effective when SUB_GID_DETERMINISTIC is set to yes.
When set to yes (WRAP MODE), allows the deterministic range calculation to wrap around using modulo arithmetic when a UID would overflow the configured subordinate ID space. The subordinate ID space is treated as a ring buffer.
WARNING: Range overlaps can lead to container escapes and privilege escalation. For example, with SUB_GID_MIN=100000, SUB_GID_MAX=200000, SUB_GID_COUNT=65536, User A (UID 1000) gets range [100000, 165535] and User B (UID 1001) wraps and overlaps with User A. User B's container can now access files from User A's containers.
Use only in development, testing, or tightly constrained lab environments.
When set to no (default), any arithmetic overflow or range exceeding SUB_GID_MAX is a hard error. This guarantees non-overlapping, monotonic allocation.
The default value for UNSAFE_SUB_GID_DETERMINISTIC_WRAP is no.
SUB_UID_MIN (number), SUB_UID_MAX (number), SUB_UID_COUNT (number)
The default values for SUB_UID_MIN, SUB_UID_MAX, SUB_UID_COUNT are respectively 100000, 600100000 and 65536.
SUB_UID_DETERMINISTIC (boolean)
start = SUB_UID_MIN + ((UID - UID_MIN) * SUB_UID_COUNT)
end = start + SUB_UID_COUNT - 1
This ensures the same UID always receives the same subordinate UID range on every system, making it suitable for environments with centralized user management (LDAP, NIS, etc.) or synchronized UIDs across systems.
If SUB_UID_DETERMINISTIC is enabled, you can use usermod --add-subuids -S to produce deterministic subuids.
WARNING: Because UID_MIN is used to calculate the ranges, any change of UID_MIN will change the ranges calculated. SUB_UID_COUNT is used to calculate the ranges, any change of SUB_UID_COUNT will change the ranges calculated. Users with identities less than UID_MIN are incompatible with SUB_UID_DETERMINISTIC, but can still be set manually.
WARNING: Do not mix deterministic and linear (default) allocation on the same system or across systems sharing /etc/subuid via network storage (NFS, etc.). Mixing allocation methods will cause subordinate ID range conflicts and overlaps .
The default value for SUB_UID_DETERMINISTIC is no.
Range Calculation Examples
With default configuration (UID_MIN=1000, SUB_UID_MIN=100000, SUB_UID_COUNT=65536):
| UID | Calculation | Subordinate UID Range |
| 1000 | 100000 + ((1000-1000) * 65536) | 100000-165535 |
| 1001 | 100000 + ((1001-1000) * 65536) | 165536-231071 |
| 1002 | 100000 + ((1002-1000) * 65536) | 231072-296607 |
| 1100 | 100000 + ((1100-1000) * 65536) | 6653600-6719135 |
Subordinate ID Space Planning
When planning subordinate ID allocation, calculate the maximum number of users the space can accommodate:
capacity = (SUB_UID_MAX - SUB_UID_MIN) / SUB_UID_COUNT
With default values: (600100000 - 100000) / 65536 ≈ 9155 users.
For high-density environments with many users and smaller allocations:
SUB_UID_COUNT 4096
SUB_UID_MIN 100000
SUB_UID_MAX 10000000
This gives: (10000000 - 100000) / 4096 ≈ 2417 users.
UNSAFE_SUB_UID_DETERMINISTIC_WRAP (boolean)
Only effective when SUB_UID_DETERMINISTIC is set to yes.
When set to yes (WRAP MODE), allows the deterministic range calculation to wrap around using modulo arithmetic when a UID would overflow the configured subordinate ID space. The subordinate ID space is treated as a ring buffer.
WARNING: Range overlaps can lead to container escapes and privilege escalation. For example, with SUB_UID_MIN=100000, SUB_UID_MAX=200000, SUB_UID_COUNT=65536, User A (UID 1000) gets range [100000, 165535] and User B (UID 1001) wraps and overlaps with User A. User B's container can now access files from User A's containers.
Use only in development, testing, or tightly constrained lab environments.
When set to no (default), any arithmetic overflow or range exceeding SUB_UID_MAX is a hard error. This guarantees non-overlapping, monotonic allocation.
The default value for UNSAFE_SUB_UID_DETERMINISTIC_WRAP is no.
SYS_GID_MAX (number), SYS_GID_MIN (number)
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)
The default value for SYS_UID_MIN (resp. SYS_UID_MAX) is 101 (resp. UID_MIN-1).
UID_MAX (number), UID_MIN (number)
The default value for UID_MIN (resp. UID_MAX) is 1000 (resp. 60000).
UMASK (number)
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 pam_umask as the default umask value.
FILE
/etc/passwd
/etc/shadow
/etc/group
/etc/gshadow
/etc/login.defs
/etc/pam.d/newusers
/etc/subgid
/etc/subuid
VEDERE ANCHE
| 30/07/2026 | shadow-utils 4.20.0 |