Linux创建用户命令-useradd

不加任何选项创建用户时根据系统版本默认用户起始UID为第一个或已创建用户UID之后为准以此递增

[root@localhost ~]# useradd user1
[root@localhost ~]# tail -1 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash

-u UID UserName：创建用户时指定用户UID；不能和现有的UID冲突

[root@localhost ~]# useradd -u 1002 user2
[root@localhost ~]# tail -2 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash

-g GID/GroupName UserName：创建用户时指定用户默认主组；前提必需是指定的组已存在，否则无法指定。

[root@localhost ~]# useradd -g 1000 user3
[root@localhost ~]# tail -3 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash

-c “注释” UserName：创建用户时指定用户信息注释

[root@localhost ~]# useradd -c 'Test User' user4
[root@localhost ~]# tail -4 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash
user4:x:1004:1004:Test User:/home/user4:/bin/bash

-d /PATH//HomeDirName UserName: 创建用户时指定目录为其家目录

[root@localhost ~]# useradd -d /home/testhome user5
[root@localhost ~]# tail -5 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash
user4:x:1004:1004:Test User:/home/user4:/bin/bash
user5:x:1005:1005::/home/testhome:/bin/bash
[root@localhost ~]# ll /home/
total 0
drwx------ 2 user5 user5 62 Jul 17 16:28 testhome
drwx------ 2 user1 user1 62 Jul 17 15:54 user1
drwx------ 2 user2 user2 62 Jul 17 15:54 user2
drwx------ 2 user3 user1 62 Jul 17 16:01 user3
drwx------ 2 user4 user4 62 Jul 17 16:04 user4

-M UserName：创建用户时不创建家目录；文件(/etc/passwd)中只是标记家目录属性但实际并不会创建家目录文件

[root@localhost ~]# useradd -M user6
[root@localhost ~]# tail -6 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash
user4:x:1004:1004:Test User:/home/user4:/bin/bash
user5:x:1005:1005::/home/testhome:/bin/bash
user6:x:1006:1006::/home/user6:/bin/bash
[root@localhost ~]# ll /home/
total 0
drwx------ 2 user5 user5 62 Jul 17 16:28 testhome
drwx------ 2 user1 user1 62 Jul 17 15:54 user1
drwx------ 2 user2 user2 62 Jul 17 15:54 user2
drwx------ 2 user3 user1 62 Jul 17 16:01 user3
drwx------ 2 user4 user4 62 Jul 17 16:04 user4

-s SHELL UserName：创建用户时指定用户的默认登录Shell类型；Shell类型可用命令(cat /etc/shells)查看(如Shell类型为/sbin/nologin为用户不可登录)

[root@localhost ~]# useradd -s /sbin/nologin user7
[root@localhost ~]# tail -7 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash
user4:x:1004:1004:Test User:/home/user4:/bin/bash
user5:x:1005:1005::/home/testhome:/bin/bash
user6:x:1006:1006::/home/user6:/bin/bash
user7:x:1007:1007::/home/user7:/sbin/nologin

-G GroupName UserName：创建用户时指定用户附加组；多组时组与组之间用逗号分隔，前提必需是指定的组已存在，否则无法指定。

[root@localhost ~]# useradd -G root user8
[root@localhost ~]# tail -8 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash
user4:x:1004:1004:Test User:/home/user4:/bin/bash
user5:x:1005:1005::/home/testhome:/bin/bash
user6:x:1006:1006::/home/user6:/bin/bash
user7:x:1007:1007::/home/user7:/sbin/nologin
user8:x:1008:1008::/home/user8:/bin/bash
[root@localhost ~]# head -1 /etc/group
root:x:0:user8

多参数组合实例：useradd -u 10010 -g 1005 -c ‘Test User2’ -d /home/testhome2 -s /sbin/nologin -G root user9

[root@localhost ~]# useradd -u 10010 -g 1005  -c 'Test User2' -d /home/testhome2 -s /sbin/nologin -G root user9
[root@localhost ~]# tail -9 /etc/passwd
user1:x:1000:1000::/home/user1:/bin/bash
user2:x:1002:1002::/home/user2:/bin/bash
user3:x:1003:1000::/home/user3:/bin/bash
user4:x:1004:1004:Test User:/home/user4:/bin/bash
user5:x:1005:1005::/home/testhome:/bin/bash
user6:x:1006:1006::/home/user6:/bin/bash
user7:x:1007:1007::/home/user7:/sbin/nologin
user8:x:1008:1008::/home/user8:/bin/bash
user9:x:10010:1005:Test User2:/home/testhome2:/sbin/nologin
[root@localhost ~]# ll /home/
total 0
drwx------ 2 user5 user5 62 Jul 17 16:28 testhome
drwx------ 2 user9 user5 62 Jul 17 16:44 testhome2
drwx------ 2 user1 user1 62 Jul 17 15:54 user1
drwx------ 2 user2 user2 62 Jul 17 15:54 user2
drwx------ 2 user3 user1 62 Jul 17 16:01 user3
drwx------ 2 user4 user4 62 Jul 17 16:04 user4
drwx------ 2 user7 user7 62 Jul 17 16:33 user7
drwx------ 2 user8 user8 62 Jul 17 16:36 user8
[root@localhost ~]# head -1 /etc/group
root:x:0:user8,user9