USERADD(8)

名称
useradd - 创建一个新用户或更新默认新用户信息

大纲

useradd [选项] 登录

useradd -D

useradd -D [选项]

描述

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).

选项

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
    任何字符串。通常是关于登录的简短描述，当前用于用户全名。

-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
    看下边，“更改默认值”子节。

-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
    密码过期后，账户被彻底禁用之前的天数。0 表示立即禁用，-1 表示禁用这个功能。

    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
    用户初始登录组的组名或号码。组名必须已经存在。组号码必须指代已经存在的组。

    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
    显示帮助信息并退出。

-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.

    如果可以，也复制 ACL 和扩展属性。

-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
    不要将用户添加到最近登录和登录失败数据库。

    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
    允许使用重复的 UID 创建用户账户。

    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.

    您应该确保密码符合系统的密码政策。

-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 /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
    创建一个和用户同名的组，并将用户添加到组中。

    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
    用户登录的 SELinux 用户。默认为留空，这会造成系统选择默认的 SELinux 用户。

  更改默认值

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
    禁用此用户账户的日期。

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

-f, --inactive INACTIVE
    密码过期到账户被禁用之前的天数。

    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
    新用户的登录 shell 名。

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

注意：

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).

CAVEATS

您可能不能想 NIS 组或 LDAP 组添加用户。这只能在相应服务器上进行。

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.

用户名不能超过 32 个字符长。

配置文件

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

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/default/useradd
    账户创建的默认值。

/etc/shadow-maint/useradd-pre.d/*, /etc/shadow-maint/useradd-post.d/*
    Run-part files to execute during user addition. The environment variable ACTION will be populated with useradd and SUBJECT with the username. useradd-pre.d will be executed prior to any user addition. useradd-post.d will execute after user addition. If a script exits non-zero then execution will terminate.

/etc/skel/
    包含默认文件的目录。

/etc/subgid
    Per user subordinate group IDs.

/etc/subuid
    Per user subordinate user IDs.

/etc/login.defs
    Shadow 密码套件配置。

退出值

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

参见

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).