First, create a user:
① basic syntax:
useradd [option] username
Common options:
-u specified uid, that uniquely identifies
-g Specifies the primary group
-G specify additional group
-d Specifies the user's home directory (by default created under / home)
Note: When you specify the home directory, the home directory of the parent directory must exist
-s Specifies the user's default shell (/ bin / sh (soft link) ==> / bin / bash (the default), / sbin / nologin: not local landing)
② verification
id Username: View user information
[root@localhost /]# useradd stu1
[root@localhost /]# id stu1
uid=1001(stu1) gid=1001(stu1) 组=1001(stu1)
[root@localhost /]# tail -3 /etc/passwd
tcpdump:x:72:72::/:/sbin/nologin
tom:x:1000:1000:tom:/home/tom:/bin/bash
stu1:x:1001:1001::/home/stu1:/bin/bash
七列：
用户名：密码占位符：用户id：用户主组id：注释：用户家目录：用户使用的shell编辑器
[root@localhost /]# tail -3 /etc/shadow
tcpdump:!!:18329::::::
tom:$6$YSwlQKVW7cJZccgB$iexoOMRAiNpukg3goSYNoOartc1sYk3A5XTPmmQMGYFIq4G2IUKi7TBe.i1b.gp1AYQNjKYgkA.zYBOkXOxh5/::0:99999:7:::
stu1:!!:18329:0:99999:7:::
第一列，用户名
第二列，加密后的密码
第三列，表示上一次修改密码的时间18329：距离linux元年（1970.1.1）的天数
第四列，表示两次密码修改最小间隔时间（天），0表示可以立可修改密码
第五列，表示密码的最大有效期（单位：天）
第六列，表示提前多少天通知密码失效
第七列，密码宽限期
第八列，密码失效时间
第九列，保留
[root@localhost /]#
③ Expansion
chage
Last update -d user password modification time
-m Change Password minimum survival (after a few days can change the password)
-M Change Password maximum survival (how many days can change the password)
-W warned a few days ago to change the password expiration
-I modification allows password expiration days
-E modify the account expiration time
-l lists the account information
[root@localhost /]# chage -l stu1
最近一次密码修改时间 ：3月 08, 2020
密码过期时间 ：从不
密码失效时间 ：从不
帐户过期时间 ：从不
两次改变密码之间相距的最小天数 ：0
两次改变密码之间相距的最大天数 ：99999
在密码过期之前警告的天数 ：7
[root@localhost /]# chage -E '2020-03-10' stu1
[root@localhost /]# chage -l stu1
最近一次密码修改时间 ：3月 08, 2020
密码过期时间 ：从不
密码失效时间 ：从不
帐户过期时间 ：3月 10, 2020
两次改变密码之间相距的最小天数 ：0
两次改变密码之间相距的最大天数 ：99999
在密码过期之前警告的天数 ：7
Second, set a password
root: a passwd username.
b. echo 密码 | passwd 用户名 --stdin / echo 密码 | passwd --stdin 用户名 (非交互式)
Enter passwd direct representation to modify the current user's password
Third, modify user information
① syntax:
usermod [options] user name
Common options:
-u Specifies the user uid, unique identifier must be unique
-g specified user's primary group
-G specify additional user groups
删除附加组：
gpasswd -d 用户名 附加组名
添加多个附加组：
usermod -aG 附加组名 用户名
-d specifies the user's home directory
Note: When you modify a user's home directory, all new home directory must exist
-s Specifies the user's default shell
After -L Lock user, locking the user can not log into the system
-U Unlock
② Case:
a.修改用户uid
[root@localhost chome]# id user1
uid=1002(user1) gid=1002(user1) 组=1002(user1)
[root@localhost chome]# usermod -u 1111 user1
[root@localhost chome]# id user1
uid=1111(user1) gid=1002(user1) 组=1002(user1)
b.修改用户的家目录
[root@localhost chome]# mkdir -p /chome/redhat/user1
[root@localhost chome]# su - user1
上一次登录：一 3月 9 09:59:07 CST 2020pts/0 上
[user1@localhost ~]$ pwd
/chome/user1
[user1@localhost ~]$ exit
登出
[root@localhost chome]# usermod -d /chome/redhat/user1 user1
[root@localhost chome]# su - user1
上一次登录：一 3月 9 10:46:36 CST 2020pts/0 上
###出现该现象
-bash-4.2$ pwd
/chome/redhat/user1
-bash-4.2$ exit
登出
###解决办法
[root@localhost chome]# cp -a /etc/skel/. /chome/redhat/user1/
[root@localhost chome]# su - user1
上一次登录：一 3月 9 10:47:17 CST 2020pts/0 上
[user1@localhost ~]$ pwd
/chome/redhat/user1
[root@localhost chome]# ls -a /etc/skel/
. .. .bash_logout .bash_profile .bashrc .mozilla
[root@localhost chome]#
-----------
修改用户家目录
usermod -md 新目录 用户名
c.修改用户的附加组
[root@localhost chome]# head -1 /etc/group
root:x:0:
[root@localhost chome]# usermod -G 0 stu1
[root@localhost chome]# head -1 /etc/group
root:x:0:stu1
d.修改用户的shell
[root@localhost /]# useradd -s /sbin/nologin stu2
[root@localhost /]# su - stu2
This account is currently not available.
[root@localhost /]# usermod -s /bin/bash stu2
[root@localhost /]# su -stu2
上一次登录：一 3月 9 11:16:53 CST 2020pts/0 上
[stu2@localhost ~]$ exit
登出
Fourth, delete users
grammar:
userdel [options] username
Common options:
-r Delete the user's home directory and delete user mailboxes (/ var / spool / mail)
-f forcibly remove a user is logged on
Fifth, group
① Create Group
groupadd [options] group name
Common options:
-g Specifies the group id, unique
[root@localhost /]# groupadd admin
[root@localhost /]# tail -1 /etc/group
admin:x:1002:
admin : x : 1002 :
组名 密码占位符 组id 用户列表
[root@localhost /]# groupadd -g 1234 system
[root@localhost /]# tail -1 /etc/group
system:x:1234:
② Delete Group
groupdel group name
Note: This group if a user's primary group can not be deleted. If only additional group, you can delete
③ group member management
gpasswd [options] user name group name (additional group)
Common options:
-a Adding users to groups (represented added)
-d remove members from a group
-A designated administrator
-M specified group members (a plurality of members separated by commas. Overwriting)
-r remove the password
gpasswd group name ==> to set password
