linux sudo su 的问题?报错

现有普通用户covapp. 使用这个用户启动apache，启动不了，加个sudo就可以执行，请问为什么？我的意思是，sudo究竟干了什么让我尅顺利执行？我man的结果是：sudo, sudoedit - execute a command as another user

看我的操作：

其一，

[covapp@station9 bin]$ pwd
/a01/software/apache/bin
[covapp@station9 bin]$ ll
total 1876
-rwxr-xr-x 1 covapp covapp    3473 Jun  8  2012 apachectl
[covapp@station9 bin]$ ./apachectl start
(13)Permission denied: make_sock: could not bind to address [::]:180
(13)Permission denied: make_sock: could not bind to address 0.0.0.0:180
no listening sockets available, shutting down
Unable to open logs
这个是无法启动的，报错Permission denied: make_sock:

其二，

[covapp@station9 bin]$ sudo ./apachectl start
[covapp@station9 bin]$ ps -ef |grep httpd
root      2122     1  0 09:40 ?        00:00:00 /a01/software/apache-2.2.14-proxy/bin/httpd -k start
covapp    2124  2122  0 09:40 ?        00:00:00 /a01/software/apache-2.2.14-proxy/bin/httpd -k start
covapp    2125  2122  0 09:40 ?        00:00:00 /a01/software/apache-2.2.14-proxy/bin/httpd -k start
covapp    2127  2122  0 09:40 ?        00:00:00 /a01/software/apache-2.2.14-proxy/bin/httpd -k start
covapp    2129  2122  0 09:40 ?        00:00:00 /a01/software/apache-2.2.14-proxy/bin/httpd -k start
这个就是运行的，程序正常。

其三，

[test@station9 bin]$ sudo -u covapp /a01/software/apache/bin/apachectl start
(13)Permission denied: make_sock: could not bind to address [::]:180
(13)Permission denied: make_sock: could not bind to address 0.0.0.0:180
no listening sockets available, shutting down
Unable to open logs
这是用另外一个用户来使用sudo命令企图执行启动命令，失败。

有没有linux高手来指导一下？或者帮忙搜索一下答案？google到现在都没google到个正确的解释。先拜谢了。