如何应用chmod 777命令获得权限以读取位于/var/log目录下的auth.log的内容

Question

 student@Ubuntu:/$ ls -l
    total 80
    drwxr-xr-x   1 root root 4096 May  9  2021 bin
    drwxr-xr-x   2 root root 4096 Apr 24  2018 boot
    drwxr-xr-x   5 root root  360 Nov 23 19:50 dev
    drwxr-xr-x   1 root root 4096 Nov 23 19:50 etc
    drwxr-xr-x   1 root root 4096 May  9  2021 home
    drwxr-xr-x   1 root root 4096 May  9  2021 lib
    drwxr-xr-x   2 root root 4096 Apr 16  2021 lib64
    drwxr-xr-x   2 root root 4096 Apr 16  2021 media
    drwxr-xr-x   2 root root 4096 Apr 16  2021 mnt
    drwxr-xr-x   1 root root 4096 May  9  2021 opt
    dr-xr-xr-x 167 root root    0 Nov 23 19:50 proc
    drwx------   1 root root 4096 May  9  2021 root
    drwxr-xr-x   1 root root 4096 May  9  2021 run
    drwxr-xr-x   1 root root 4096 May  9  2021 sbin
    drwxr-xr-x   2 root root 4096 Apr 16  2021 srv
    dr-xr-xr-x  13 root root    0 Nov 23 19:50 sys
    drwxrwxrwt   1 root root 4096 Nov 23 19:52 tmp
    drwxr-xr-x   1 root root 4096 Apr 16  2021 usr
    drwxr-xr-x   1 root root 4096 Apr 16  2021 var
    student@Ubuntu:/$ cd tmp
    student@Ubuntu:/tmp$ cat /var/log/auth.log
    cat: /var/log/auth.log: Permission denied
    student@Ubuntu:/tmp$ cd ..
    student@Ubuntu:/$ cd sys
    student@Ubuntu:/sys$ cat /var/log/auth.log
    cat: /var/log/auth.log: Permission denied
    student@Ubuntu:/sys$ chmod 777 sys
    chmod: cannot access 'sys': No such file or directory
    student@Ubuntu:/sys$ cd ..
    student@Ubuntu:/$ chmod 777 sys
    chmod: changing permissions of 'sys': Read-only file system
    student@Ubuntu:/$ chmod 777 var
    chmod: changing permissions of 'var': Operation not permitted

Answer 1

如果您想查看/var/log/auth.log的内容，只需使用sudo-command：

sudo cat /var/log/auth.log

将提示您输入密码，然后显示文件的内容。

不要更改系统文件的权限，您很容易就会重新安装操作系统。

或者，您可以将用户添加到adm-group中

sudo adduser $USER adm

然后是注销/登录，组在login时被应用。

这样就没有必要使用sudo-command了。