Users and user groups
1 Linux Users
Linux is a multi-user operating system, different users have different permissions, you can view and manipulate different files. Ubuntu has three users:
1 first-time users created; 2 root user; 3 ordinary users;
User rights for the first time create more than the average user, but no more than the root user.
linux users logged in / etc / passwd this document; linux user passwords recorded in the / etc / shadow this document; each user has an ID, called the UID.
// 查看用户记录
ding@ding-ubuntu:~$ cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
......
gdm:x:121:125:Gnome Display Manager:/var/lib/gdm3:/bin/false
ding:x:1000:1000:ding,,,:/home/ding:/bin/bash2 Linux User Group
For administrative purposes, the user group. So that you can set up a non-person in this group can not access certain files. Each user can belong to a plurality of different groups.
Users and User Group Description:
User : home with you, brother, sister individual, each person has their own room, you three are the user, you can not just shuffle of someone else's room;
User Groups : You are a family of three, that is, belong to the same user group, the three of you can share a kitchen, study space;
therefore:
Users and groups present is to control access to the file, each group of users has an ID, the GID is called, the user group information is stored in / etc / group file. As follows:
ding@ding-ubuntu:/etc$ cat group
root:x:0:
daemon:x:1:
bin:x:2:
sys:x:3:
sudo:x:27:ding // ding 为 sudo 这个用户组的成员
......
// ding为用户组名，x为密码信息，1000为用户组ID，最后的:后为用户组成员
ding:x:1000:
sambashare:x:126:dingCan be seen, multiple users can belong to user groups.
3 Create a user group
A graphical user interface installation
Installation tools: sudo apt-get install gnome-system-tools
2 command line to create users and user groups
Add user
添加用户：adduser 用户名
用户查询：finger 用户名
修改用户密码：passwd 用户名
删除用户：deluser 用户名Adding users and user testing queries:
// 创建用户
ding@ding-ubuntu:~$ sudo adduser ding_u2
[sudo] ding 的密码：
正在添加用户"ding_u2"...
正在添加新组"ding_u2" (1001)...
正在添加新用户"ding_u2" (1001) 到组"ding_u2"...
创建主目录"/home/ding_u2"...
正在从"/etc/skel"复制文件...
输入新的 UNIX 密码：
重新输入新的 UNIX 密码：
passwd：已成功更新密码
正在改变 ding_u2 的用户信息
请输入新值，或直接敲回车键以使用默认值
全名 []:
房间号码 []:
工作电话 []:
家庭电话 []:
其它 []:
这些信息是否正确？ [Y/n] y
// 查询用户信息
ding@ding-ubuntu:~$ finger ding_u2
Login: ding_u2 Name:
Directory: /home/ding_u2 Shell: /bin/bash
Never logged in.
No mail.
No Plan.Add User Group
添加用户组：addgroup 用户组名
显示组内用户名：groups 用户组名
删除用户组：delgroup 用户组名Adding user groups and delete a user group test:
// 添加用户组
ding@ding-ubuntu:/home$ sudo addgroup ding_g2
正在添加组"ding_g2" (GID 1001)...
完成。
// 查看 ding 用户组内用户
ding@ding-ubuntu:/home$ groups ding // 查看 ding 这个用户组
ding : ding adm cdrom sudo dip plugdev lpadmin sambashare
// 查看刚创建的用户组的用户
ding@ding-ubuntu:/home$ sudo groups ding_g2
groups: "ding_g2": no such user // 没有用户，因为刚创建完还没添加
// 删除用户组
ding@ding-ubuntu:/home$ sudo delgroup ding_g2
正在删除组 'ding_g2'...
完成。
authority management
1 file privilege allows users to different users or groups of users to have a file, the file permissions are divided into three types:
r: Read; w: Write; x: executable;
-rw-r - r-- is the file permissions, the first indicating the file type, and the remaining three each represents a set of permissions. Respectively the owner permission , the owner's group permissions , other permissions .
Binary file permissions can be expressed: r = 4; w = 2; x = 1;
Permissions test.c file:
ding@ding-ubuntu:~$ ls -l test.c
-rw-r--r-- 1 ding ding 121 2月 8 21:34 test.c
权限说明：
所属用户拥有读写权限无可执行权限；
组内其他用户拥有读权限 无写权限 无可执行权限；
其他用户仅有可读权限；
用户和用户组说明：
第一个 ding 表示所属用户；
第二个 ding 表示所属用户组；Look at a file system privileges Description:
ding@ding-ubuntu:/dev$ ls -l vcsu
crw-rw---- 1 root tty 7, 64 2月 8 21:26 vcsu
权限说明：
所属用户为 root 用户，拥有 读写权限 无可执行权限；
所属用户组为 tty，即 tty 这个组内的所有成员都有 读写权限 无可执行权限；
其他用户为 ---，对 vcsu 文件无任何权限；2 Linux file permissions to modify
Modify file permissions command: chmod
Users modify the file belongs: chown
Modify the file permissions test:
ding@ding-ubuntu:~$ ls -l test.c // 查看 test.c 文件的权限
-rw-r--r-- 1 ding ding 113 2月 8 23:43 test.c
// 所属用户为ding，用户组为ding
ding@ding-ubuntu:~$ cat test.c // 源文件
/* 测试文件 */
#include <stdio.h>
int main(int argc, char argv[])
{
printf("hello world\n");
return 0;
}
ding@ding-ubuntu:~$ gcc test.c -o test // 使用 gcc 编译 test.c
ding@ding-ubuntu:~$ ls -l test* // 查看 test可执行文件和 test.c 的权限
-rwxr-xr-x 1 ding ding 8296 2月 8 23:49 test // test文件可执行
-rw-r--r-- 1 ding ding 113 2月 8 23:43 test.c
ding@ding-ubuntu:~$ ./test // test 执行结果
hello world
// 修改权限：可读可写，不可执行
ding@ding-ubuntu:~$ chmod 664 test
ding@ding-ubuntu:~$ ls -l test*
-rw-rw-r-- 1 ding ding 8296 2月 8 23:49 test // 权限改变
-rw-r--r-- 1 ding ding 113 2月 8 23:43 test.c
ding@ding-ubuntu:~$ ./test
bash: ./test: 权限不够 // 当前 test 文件因权限不够无法执行Modify the file belongs to a user, the command format is as follows:
sudo chown 修改用户：修改组 文件Modify test files users and groups:
ding@ding-ubuntu:~$ ls -l test // test属于ding用户，所属组为ding
-rwxrwxr-- 1 ding ding 8296 2月 8 23:49 test
// 用户修改为ding，所属组不变
ding@ding-ubuntu:~$ sudo chown root:ding test
[sudo] ding 的密码：
ding@ding-ubuntu:~$ ls -l test
-rwxrwxr-- 1 root ding 8296 2月 8 23:49 test // 用户成功变为root
ding@ding-ubuntu:~$ sudo chown ding:root test
// 用户变为ding，所属组变为root
ding@ding-ubuntu:~$ ls -l test
-rwxrwxr-- 1 ding root 8296 2月 8 23:49 test // 权限结果
