1、创建环境
mkdir -p /oldboy
echo 'hostname' > /oldboy/oldwang.sh
chown oldboy.oldboy /oldboy/oldwang.sh
2、文件的R权限
###root 用户下面 修改权限 文件的r
[root@oldboyedu42-lnb oldboy]# ll oldwang.sh
-rw-r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh
[root@oldboyedu42-lnb oldboy]# chmod u=r oldwang.sh
[root@oldboyedu42-lnb oldboy]# ll oldwang.sh
-r--r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh
###oldboy用户测试
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
hostname
[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh
-bash: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh
-bash: /oldboy/oldwang.sh: Permission denied
3、文件的W权限
###root 用户下面 修改权限 文件的w
[root@oldboyedu42-lnb oldboy]# ll oldwang.sh
-r--r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh
[root@oldboyedu42-lnb oldboy]# chmod u=w oldwang.sh
[root@oldboyedu42-lnb oldboy]# ll oldwang.sh
--w-r--r-- 1 oldboy oldboy 9 Nov 3 18:12 oldwang.sh
###oldboy 用户
[oldboy@oldboyedu42-lnb oldboy]$ ll /oldboy/oldwang.sh
--w-r--r-- 1 oldboy oldboy 9 Nov 3 18:12 /oldboy/oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ cat /oldboy/oldwang.sh
cat: /oldboy/oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh
-bash: /oldboy/oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh
~
~
~
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ ll oldwang.sh
w-r--r-- 1 oldboy oldboy 21 Nov 3 18:23 oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh
alias rm
~
~
~
"oldwang.sh" 1L, 9C written
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
cat: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
cat: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
cat: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
cat: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ ll oldwang.sh
--wxr--r-- 1 oldboy oldboy 9 Nov 3 18:25 oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh
~
~
~
~
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
ias rm
[oldboy@oldboyedu42-lnb oldboy]$ vim oldwang.sh
alias rm
pwd
~
~
~
~
"oldwang.sh" 2L, 13C written
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
alias rm
pwd
小结：
对于文件的w权限
1.修改文件的内容，w权限需要有人r权限配合
2.如果没有r权限，使用vi/vim 修改文件内容 会导致源文件内容清空
3、文件的X权限
###root 用户下面 修改权限 文件的x
[root@oldboyedu42-lnb oldboy]# chmod u=x oldwang.sh
[root@oldboyedu42-lnb oldboy]# ll oldwang.sh
---xr--r-- 1 oldboy oldboy 13 Nov 3 18:29 oldwang.sh
###oldboy
[oldboy@oldboyedu42-lnb oldboy]$ ll oldwang.sh
---xr--r-- 1 oldboy oldboy 13 Nov 3 18:29 oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$ cat oldwang.sh
cat: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ echo 'pwd' >>oldwang.sh
-bash: oldwang.sh: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh
bash: /oldboy/oldwang.sh: Permission denied
4、文件的rx权限
###root 用户下面 修改权限 文件的rx
[root@oldboyedu42-lnb oldboy]# ll oldwang.sh
-r-xr--r-- 1 oldboy oldboy 13 Nov 3 18:29 oldwang.sh
###oldboy
[oldboy@oldboyedu42-lnb oldboy]$ cat /oldboy/oldwang.sh
pwd
[oldboy@oldboyedu42-lnb oldboy]$ /oldboy/oldwang.sh
/oldboy
[oldboy@oldboyedu42-lnb oldboy]$ ll /oldboy/oldwang.sh
-r-xr--r-- 1 oldboy oldboy 4 Nov 3 18:34 /oldboy/oldwang.sh
[oldboy@oldboyedu42-lnb oldboy]$
下面为何报错的原因是什么？
[oldboy@oldboyedu42-lnb oldboy]$ echo '#' >> /etc/hosts
-bash: /etc/hosts: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ echo '#' >> /etc/hosts
-bash: /etc/hosts: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ ls -l /etc/hosts
-rw-r--r--. 2 root root 194 Nov 11 2017 /etc/hosts
[oldboy@oldboyedu42-lnb oldboy]$ #oldboy用户
[oldboy@oldboyedu42-lnb oldboy]$ #oldboy用户与这个文件关系: 陌生人
[oldboy@oldboyedu42-lnb oldboy]$ id oldboy
uid=500(oldboy) gid=500(oldboy) groups=500(oldboy)
[oldboy@oldboyedu42-lnb oldboy]$
[oldboy@oldboyedu42-lnb oldboy]$ #oldboy用户对这个文件权限 最后三位 r--
[oldboy@oldboyedu42-lnb oldboy]$ cat /etc/shadow
cat: /etc/shadow: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ cat /etc/sudoers
cat: /etc/sudoers: Permission denied
[oldboy@oldboyedu42-lnb oldboy]$ ll /etc/sudoers
-r--r-----. 1 root root 3729 Dec 8 2015 /etc/sudoers
#1.oldboy
#2.oldboy 陌生人
#3.最后三位 ---
5、文件的读写执行小结(限制普通用户)：
1.r查看文件的内容
2.w修改文件的内容，需要r的配合
如果没有r权限，使用vi/vim 修改文件内容 会导致源文件内容清空
3.x执行文件（命令或脚本），需要r的配合
练习题：
详细说出rwx在文件中的意义