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

       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).

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. The directory HOME_DIR does not have to exist but will not be
           created if it is missing.

       -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
           用户初始登陆组的组名或号码。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
           现实帮助信息并退出。

       -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.

           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
           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
           用户登陆的 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.

       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.

       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/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).