NEWUSERS(8)

System Management Commands

NEWUSERS(8)

名称

newusers - 批量更新和创建新用户

大纲

newusers [options] [file]

描述

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

这是用户的用户名。

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

If this field is not empty, it will be encrypted and used as the new value of the encrypted password.

pw_uid

此字段用于定义用户的 UID。

If the field is empty, a new (unused) UID will be defined automatically by newusers.

如果此字段包含一个数字，此数字会用于 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.

如果一个现有用户更改了 UID，此用户的文件所有权需要手动修复。

pw_gid

此字段用于定义用户的主组 ID。

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.

如果此字段是一个数字，此数字会被用作此用户的主组 ID。如果没有对应此 GID 的现有组，将会使用此 GID 创建一个新组，名称和用户名相同。

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

此字段复制到用户的 GECOS 字段。

pw_dir

此字段用于定义用户的主目录。

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

此字段定义了用户的 shell。对此字段不进行任何检查。

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.

During this first pass, users are created with a locked password (and passwords are not changed for the users which are not created). A second pass is used to update the passwords using PAM. Failures to update a password are reported, but will not stop the other password updates.

此命令一般用于在大型的应用环境中，对大量账户进行一次性更新。

选项

The options which apply to the newusers command are:

--badname

Allow names that do not conform to standards.

-h, --help

显示帮助信息并退出。

-r, --system

创建一个系统账户。

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

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.

CAVEATS

输入文件必须受到保护，因为它包含未加密的密码。

配置文件

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

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.

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).

默认值是 0，意味着组中的成员数没有限制。

此功能(分割组)允许限制组文件中的行长度。这对于确保 NIS 组的行比长于 1024 字符。

如果要强制这个限制，可以使用 25。

注意：分割组可能不受所有工具的支持(甚至在 Shadow 工具集中)。您不应该使用这个变量，除非真的需要。

PASS_MAX_DAYS (number)

一个密码可以使用的最大天数。如果密码比这旧，将会强迫更改密码。如果不指定，就假定为 -1，这会禁用这个限制。

PASS_WARN_AGE (number)

The number of days warning given before a password expires. A zero means warning is given only upon the day of expiration, a value of -1 means no warning is given. If not specified, no warning will be provided.

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_GID_DETERMINISTIC (boolean)

If set to yes, the commands useradd, usermod, and newusers will calculate subordinate GID ranges deterministically based on the user's UID instead of searching for the next free range. The formula used is:

      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)

WARNING: SECURITY RISK - MAY CAUSE RANGE OVERLAPS AND PRIVILEGE ESCALATION!

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)

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.

SUB_UID_DETERMINISTIC (boolean)

If set to yes, the commands useradd, usermod, and newusers will calculate subordinate UID ranges deterministically based on the user's UID instead of searching for the next free range. The formula used is:

      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)

WARNING: SECURITY RISK - MAY CAUSE RANGE OVERLAPS AND PRIVILEGE ESCALATION!

Only effective when SUB_UID_DETERMINISTIC is set to yes.

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)

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)

文件模式创建掩码初始化为此值。如果没有指定，掩码初始化为 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 pam_umask as the default umask value.

文件

/etc/passwd

用户账户信息。

/etc/shadow

安全用户账户信息。

/etc/group

组账户信息。

/etc/gshadow

安全组账户信息。

/etc/login.defs

Shadow 密码套件配置。

/etc/pam.d/newusers

PAM configuration for newusers.

/etc/subgid

Per user subordinate group IDs.

/etc/subuid

Per user subordinate user IDs.

参见

2026-07-30

shadow-utils 4.20.0