目录访问权限问题

By [e-mail]

为了打开文件 temp/txt ,需要对当前工作目录 .、temp/目录具有执行权限。然后对该文件temp/txt还要有想应权限，
这取决于你以何种模式打开它（只读、读写等）。

但是这个对于root用户来说，似乎不起作用。可以看下面的实验

[zieckey@localhost ~]$ mkdir temp
[zieckey@localhost ~]$ ls
temp
[zieckey@localhost ~]$ echo aaaaa > temp/txt
[zieckey@localhost ~]$ ls temp/
txt
[zieckey@localhost ~]$ cat temp/txt
aaaaa
[zieckey@localhost ~]$ ll temp/
总计 8
-rw-rw-r-- 1 zieckey zieckey 6 10-05 15:10 txt
[zieckey@localhost ~]$ chmod a-r temp/txt
[zieckey@localhost ~]$ cat temp/txt
cat: temp/txt: 权限不够
[zieckey@localhost ~]$ echo BBBB >> temp/txt
[zieckey@localhost ~]$ cat temp/txt
cat: temp/txt: 权限不够
[zieckey@localhost ~]$ chmod a+r temp/txt
[zieckey@localhost ~]$ cat temp/txt
aaaaa
BBBB
[zieckey@localhost ~]$ echo ccccc >> temp/txt
[zieckey@localhost ~]$ cat temp/txt
aaaaa
BBBB
ccccc
[zieckey@localhost ~]$ chmod a-w temp/txt
[zieckey@localhost ~]$ echo ddddddd >> temp/txt
bash: temp/txt: 权限不够
[zieckey@localhost ~]$ ll
总计 8
drwxrwxr-x 2 zieckey zieckey 4096 10-05 15:10 temp
[zieckey@localhost ~]$ chmod a-x temp/
[zieckey@localhost ~]$ cd temp/
bash: cd: temp/: 权限不够
[zieckey@localhost ~]$ cat temp/txt
cat: temp/txt: 权限不够
[zieckey@localhost ~]$ ll
总计 8
drw-rw-r-- 2 zieckey zieckey 4096 10-05 15:10 temp
[zieckey@localhost ~]$
[zieckey@localhost ~]$ su root
口令：
[root@localhost zieckey]# ll temp/txt
-r--r--r-- 1 zieckey zieckey 17 10-05 15:12 temp/txt
[root@localhost zieckey]# cat temp/txt
aaaaa
BBBB
ccccc
[root@localhost zieckey]# ll temp
总计 8
-r--r--r-- 1 zieckey zieckey 17 10-05 15:12 txt
[root@localhost zieckey]# ll
总计 8
drw-rw-r-- 2 zieckey zieckey 4096 10-05 15:10 temp
[root@localhost zieckey]# chmod a-rwx temp/
[root@localhost zieckey]# cat temp/txt
aaaaa
BBBB
ccccc
[root@localhost zieckey]#

对于root用户，即使所有的权限都没有了‘chmod a-rwx temp/’ 也能对该temp/目录进行任何操作。这难道就是root用户的超级权限吗？