禁止本机对PING 响应

echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all

但如果在bash command line上运行该命令，必须为root ;

若通过bash script 运行，必须

chown  root:root script;

chmod 777  script;

之后才 echo XXX |  sudo /P/A/T/H/script

扩展思考：

[jim@jim shell]$ ll /proc/sys/net/ipv4/icmp_echo_ignore_all 

-rw-r--r-- 1 root root 0 Apr 17 14:01 /proc/sys/net/ipv4/icmp_echo_ignore_all

[jim@jim shell]$ stat /proc/

  File: `/proc/'

  Size: 0         Blocks: 0          IO Block: 1024   directory

Device: 3h/3d Inode: 1           Links: 201

Access: (0555/dr-xr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)

Access: 2011-04-17 11:14:54.001999760 +0800

Modify: 2011-04-17 11:14:54.001999760 +0800

Change: 2011-04-17 11:14:54.001999760 +0800

以非root id 运行 (fail)：

[jim@jim shell]$ echo '1'  >  /proc/sys/net/ipv4/icmp_echo_ignore_all 

bash: /proc/sys/net/ipv4/icmp_echo_ignore_all: Permission denied

以root id 运行 (success)：

[root@jim sudo-1.8.1p1]# echo '1' >  /proc/sys/net/ipv4/icmp_echo_ignore_all 

[root@jim sudo-1.8.1p1]# 

以非root id sudo 运行 （fail）

[jim@jim shell]$ sudo echo '1'  >  /proc/sys/net/ipv4/icmp_echo_ignore_all 

bash: /proc/sys/net/ipv4/icmp_echo_ignore_all: Permission denied

以非root 运行root的script ,success:

[jim@jim shell]$ cat ignore_ping.bash 

#!/bin/bash

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

[jim@jim shell]$ stat ignore_ping.bash 

  File: `ignore_ping.bash'

  Size: 61         Blocks: 8          IO Block: 4096   regular file

Device: 802h/2050d Inode: 280314      Links: 1

Access: (0777/-rwxrwxrwx)  Uid: (    0/    root)   Gid: (    0/    root)

Access: 2011-04-17 13:26:09.446376003 +0800

Modify: 2011-04-17 13:22:02.187376003 +0800

Change: 2011-04-17 13:25:54.945376002 +0800

[jim@jim shell]$ sudo ./ignore_ping.bash 

[sudo] password for jim: 

[jim@jim shell]$