Linux account management detailed

First, the user account management

1, an overview of user accounts

Linux to control access to resources based on user identity.

2, user account management

1) user account

• Superuser (the root);

• general user;

• Program users;

• UID (User IDentify) user identification number;

① user accounts file / etc / passwd

/ Etc / passwd file used to store user name, home directory, basic information log Shell and the like; each row corresponds to a user's account records. As shown below:

② user accounts file / etc / shadow

/ Etc / shadow file to save user's password information, the account expiration date, each row corresponds to a user's password record. As shown below:

3, add user accounts

Add user accounts common commands and options in the following format:

Application examples:

<!--创建bob用户，管理组为root，附加组为root，指定宿主目录为/bob-->
[root@01 ~]# useradd -d /bob -g root -G root bob
[root@centos01 ~]# tail -2 /etc/passwd
dhcpd:x:177:177:DHCP server:/:/sbin/nologin
bob:x:1001:0::/bob:/bin/bash
<!--创建tom用户，不需要创建宿主目录，账户不能登录系统-->
[root@centos01 ~]# useradd -M -s /sbin/nologin tom
[root@centos01 ~]# tail -2 /etc/passwd
bob:x:1001:0::/bob:/bin/bash
tom:x:1002:1002::/home/tom:/sbin/nologin

4, set / change user password passwd

Set / change user passwords basic command syntax and format commonly used options are as follows:

Application examples:

[root@centos01 ~]# passwd bob  <!--账户设置密码-->
更改用户 bob 的密码 。
新的 密码：  <!--输入密码-->
无效的密码： 密码未通过字典检查 - 过于简单化/系统化
重新输入新的 密码：      <!--确定密码-->
passwd：所有的身份验证令牌已经成功更新。
[root@centos01 ~]# passwd -l bob    <!--锁定用户-->
锁定用户 bob 的密码 。
passwd: 操作成功
[root@centos01 ~]# passwd -S bob  <!--查看用户是否锁定-->
bob LK 2020-01-11 0 99999 7 -1 (密码已被锁定。)
[root@centos01 ~]# passwd -u bob   <!--解锁用户-->
解锁用户 bob 的密码。
passwd: 操作成功
[root@centos01 ~]# passwd -S bob      <!--查看用户状态是否解锁-->
bob PS 2020-01-11 0 99999 7 -1 (密码已设置，使用 SHA512 算法。)
[root@centos01 ~]# passwd -d bob      <!--清空账户密码-->
清除用户的密码 bob。
passwd: 操作成功
[root@centos01 ~]# userdel -r bob    <!--删除账户和宿主目录-->
[root@centos01 ~]# tail -2 /etc/passwd
dhcpd:x:177:177:DHCP server:/:/sbin/nologin
tom:x:1002:1002::/home/tom:/sbin/nologin

5, the initial user account profiles

When a new user account file derived from the / etc / skel directory is copied; initial primary user profile is as follows:

• ~ / .Bash_profile: each execution login.

• ~ / .Bashrc: executed every time you enter a new Bash environment.

• ~ / .Bash_logout: Log execute every time.

Second, the management group accounts

1, group account overview

• Basic group (private group);

• Additional groups (public group);

• GID: group identification number

1) group accounts file / etc / group

/ Etc / group file is used to save the set of basic account information; follows:

[root@centos01 ~]# cat /etc/group
root:x:0:
bin:x:1:
daemon:x:2:
sys:x:3:
adm:x:4:
tty:x:5:
............         <!--此处省略部分内容-->

2) group accounts file / etc / gshadow

/ Etc / gshadow group accounts for recording the password information; follows:

[root@centos01 ~]# cat /etc/gshadow
root:::
bin:::
daemon:::
sys:::
adm:::
tty:::
............         <!--此处省略部分内容-->

2, add group accounts groupadd

Add a group account command of basic format is as follows:

Application examples:

[root@centos01 ~]# groupadd -g 200 accp
[root@centos01 ~]# tail -3 /etc/group
tcpdump:x:72:
test:x:1000:
accp:x:200:
[root@centos01 ~]# groupadd benet
[root@centos01 ~]# tail -3 /etc/group
dhcpd:x:177:
tom:x:1002:
benet:x:1003:

3, add, delete group members gpasswd

Set group account password, add / remove group members; basic format commonly used options and commands are as follows:

Application examples:

[root@centos01 ~]# gpasswd -a bob benet<!--将用户加入到组中（自行创建bob用户）-->
正在将用户“bob”加入到“benet”组中
[root@centos01 ~]# tail -2 /etc/group
tom:x:1002:
benet:x:1003:bob
[root@centos01 ~]# gpasswd -M tom,lisi benet   <!--批量添加用户到benet组中 -->
[root@centos01 ~]# tail -2 /etc/group
benet:x:1003:tom,lisi
lisi:x:1004:
[root@centos01 ~]# gpasswd -d tom benet <!--将tom用户退出benet组-->
正在将用户“tom”从“benet”组中删除
[root@centos01 ~]# tail -2 /etc/group
benet:x:1003:lisi
lisi:x:1004:

4, delete group accounts groupdel

The basic format of the command to delete the group accounts as follows:

Application examples:

[root@centos01 ~]# groupdel benet  <!--删除benet组-->

5. When you add user accounts specified group

useradd command "-g" substantially option specifies the group name of the user (number or GID); - a user option to specify a "G" additional set name (number or GID).

Application examples:

<!--创建bob用户，管理组为root，附加组为root，指定宿主目录为/bob-->
[root@centos01 ~]# useradd -d /bob -g root -G root bob
[root@centos01 ~]# tail -2 /etc/passwd
dhcpd:x:177:177:DHCP server:/:/sbin/nologin
bob:x:1001:0::/bob:/bin/bash

6, query account information

1) id command

id to query a user identity; basic command syntax is as follows:

Application examples:

[root@centos01 ~]# id bob    <!--查看用户的详细信息-->
uid=1003(bob) gid=0(root) 组=0(root),1005(benet)

2) groups command

groups command to query the user belongs; basic command syntax is as follows:

Application examples:

[root@centos01 ~]# groups bob  <!--查询用户所属组-->
bob : root benet

3) finger command

For more information about the finger command to query the user account for; basic command syntax is as follows:

4) users, w and who command

users, w, and who command queries the user information logged into the host. Application examples are as follows:

[root@centos01 ~]# users
root
[root@centos01 ~]# w
 01:57:23 up 53 min,  1 user,  load average: 0.00, 0.01, 0.01
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
root     pts/0    192.168.100.254  01:04    3.00s  0.05s  0.00s w
[root@centos01 ~]# 
[root@centos01 ~]# who
root     pts/0        2020-01-17 01:04 (192.168.100.254)