如何让普通用户获取root用户的权限

sudo 是 Linux 系统管理指令，是允许系统管理员让普通用户执行一些或者全部的 root 命令的一个工具，如 halt，reboot，su 等等。这样不仅减少了 root 用户的登录 和管理时间，同样也提高了安全性。sudo不是对 shell 的一个代替，它是面向每个命令的。

sudo 的特点

限制用户执行指定的命令
记录用户执行的每一条命令
配置文件（/etc/sudoers）提供集中的用户管理、权限与主机等参数
验证密码的后5分钟内（默认值）无须再让用户再次验证密码

实战演练

环境：Red Hat Enterprise Linux Server release 7.3

1. 测试普通用户能否删除 root 用户创建的文件

[root@localhost ~]# mkdir /test
[root@localhost ~]# cd /test
[root@localhost test]# touch test.txt
[root@localhost test]# mkdir test.dir
[root@localhost test]# ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 02:19 test.dir
-rw-r--r--. 1 root root 0 Jul 18 02:19 test.txt
[root@localhost test]# id test
uid=1004(test) gid=1005(test) groups=1005(test)
[root@localhost test]# su - test
Last login: Thu Jul 18 02:17:11 EDT 2019 on pts/0
[test@localhost ~]$ cd /test
[test@localhost test]$ ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 02:19 test.dir
-rw-r--r--. 1 root root 0 Jul 18 02:19 test.txt
[test@localhost test]$ rm -rf test.dir/
rm: cannot remove ‘test.dir/’: Permission denied
[test@localhost test]$ rm -rf test.txt 
rm: cannot remove ‘test.txt’: Permission denied
[test@localhost test]$ ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 02:19 test.dir
-rw-r--r--. 1 root root 0 Jul 18 02:19 test.txt

2. 用 visudo 命令配置 sudo

[root@localhost ~]# visudo
# 在 /etc/sudoers 配置文件中 root    ALL=(ALL)       ALL 这一行下面加入 test    ALL=(ALL)       ALL
[root@localhost ~]# cat /etc/sudoers | grep ALL
Defaults    env_keep += "LC_TIME LC_ALL LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY"
root    ALL=(ALL)       ALL
test    ALL=(ALL)       ALL
# %sys ALL = NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS
%wheel  ALL=(ALL)       ALL
# %wheel        ALL=(ALL)       NOPASSWD: ALL
%wheel  ALL=(ALL)       NOPASSWD: ALL
# %users  ALL=/sbin/mount /mnt/cdrom, /sbin/umount /mnt/cdrom

3. 普通用户结合 sudo 删除 root 用户的文件

[root@localhost ~]# echo "Jaking" | passwd --stdin test
Changing password for user test.
passwd: all authentication tokens updated successfully.
[root@localhost ~]# su - test
Last login: Thu Jul 18 02:34:50 EDT 2019 on pts/0
[test@localhost ~]$ cd /test/
[test@localhost test]$ ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 02:19 test.dir
-rw-r--r--. 1 root root 0 Jul 18 02:19 test.txt
[test@localhost test]$ rm -rf test.dir/
rm: cannot remove ‘test.dir/’: Permission denied
[test@localhost test]$ rm -rf test.txt 
rm: cannot remove ‘test.txt’: Permission denied
[test@localhost test]$ sudo rm -rf test.dir/
[sudo] password for test: 
[test@localhost test]$ ll
total 0
-rw-r--r--. 1 root root 0 Jul 18 02:19 test.txt
[test@localhost test]$ sudo rm -rf test.txt 
[test@localhost test]$ ll
total 0

4. sudo 免密配置

[test@localhost test]$ sudo cat /etc/shadow
[sudo] password for test: 
root:$6$YZrm6scxO5zzICbR$fOzORb.0Ib9POZzJmrnzOGDqfFySp8X.9p5QpcpnJXWHIJvZcFpXQONyNigwrZbhXtyfnFn5F1mJsdkXS3jEF/::0:99999:7:::
bin:*:16925:0:99999:7:::
daemon:*:16925:0:99999:7:::
adm:*:16925:0:99999:7:::
***省略部分输出信息***
[test@localhost test]$ id test2
uid=1006(test2) gid=1007(test2) groups=1007(test2)
[root@localhost ~]# visudo
# 在 /etc/sudoers 配置文件中 %wheel  ALL=(ALL)       NOPASSWD: ALL 这一行的下面 加入test ALL=(ALL)       NOPASSWD: ALL
[root@localhost ~]# cat /etc/sudoers | grep NOPASSWD
# %wheel        ALL=(ALL)       NOPASSWD: ALL
%wheel  ALL=(ALL)       NOPASSWD: ALL
test ALL=(ALL)       NOPASSWD: ALL
[test@localhost ~]$ sudo cat /etc/shadow
# 用普通用户查看 /etc/shadow 文件已经不需要再输入当前登录用户的密码
root:$6$YZrm6scxO5zzICbR$fOzORb.0Ib9POZzJmrnzOGDqfFySp8X.9p5QpcpnJXWHIJvZcFpXQONyNigwrZbhXtyfnFn5F1mJsdkXS3jEF/::0:99999:7:::
bin:*:16925:0:99999:7:::
daemon:*:16925:0:99999:7:::
adm:*:16925:0:99999:7:::
***省略部分输出信息***

5. 配置 sudo 的部分权限

[root@localhost ~]# cd /tmp
[root@localhost tmp]# rm -rf *
[root@localhost tmp]# ll
total 0
[root@localhost tmp]# touch file
[root@localhost tmp]# mkdir dir
[root@localhost tmp]# ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 03:01 dir
-rw-r--r--. 1 root root 0 Jul 18 03:01 file
[root@localhost tmp]# whereis cat
cat: /usr/bin/cat /usr/share/man/man1/cat.1.gz
[root@localhost tmp]# visudo
# 把 /etc/sudoers 配置文件中的 test    ALL=(ALL)       ALL 改为 test    ALL=(ALL)       /usr/bin/cat
[root@localhost ~]# cat /etc/sudoers | grep cat
## Updating the locate database
# Defaults specification
# Preserving HOME has security implications since many programs
test    ALL=(ALL)       /usr/bin/cat
[root@localhost ~]# su - test
Last login: Thu Jul 18 03:06:55 EDT 2019 on pts/0
[test@localhost ~]$ sudo cat /etc/shadow
# 给 test 用户配置了查看权限
root:$6$YZrm6scxO5zzICbR$fOzORb.0Ib9POZzJmrnzOGDqfFySp8X.9p5QpcpnJXWHIJvZcFpXQONyNigwrZbhXtyfnFn5F1mJsdkXS3jEF/::0:99999:7:::
bin:*:16925:0:99999:7:::
daemon:*:16925:0:99999:7:::
adm:*:16925:0:99999:7:::
***省略部分输出信息***
[test@localhost ~]$ cd /tmp
[test@localhost tmp]$ ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 03:06 dir
-rw-r--r--. 1 root root 0 Jul 18 03:01 file
[test@localhost tmp]$ rm -rf dir
# test 用户已经没有了删除权限
rm: cannot remove ‘dir’: Permission denied
[test@localhost tmp]$ rm -rf file 
# test 用户已经没有了删除权限
rm: cannot remove ‘file’: Permission denied
[test@localhost tmp]$ ll
total 0
drwxr-xr-x. 2 root root 6 Jul 18 03:06 dir
-rw-r--r--. 1 root root 0 Jul 18 03:01 file