[1217166816] HOST NOTIFICATION: sery;mail-server;DOWN;host-notify-by-email;CRITICAL - Plugin timed out after 10 seconds
[1217166816] Warning: Attempting to execute the command "/usr/bin/printf "%b" "***** Nagios 2.9 *****\n\nNotification Type: PROBLEM\nHost: mail-server\nState: DOWN\nAddress: 211.155.115.66\nInfo: CRITICAL - Plugin timed out after 10 seconds\n\nDate/Time: Sun Jul 27 13:53:36 UTC 2008\n" | /bin/mail -s "Host DOWN alert for mail-server!" ABC@163.com" resulted in a return code of 127.  Make sure the script or binary you are trying to execute actually exists...

　　其他的行也更这个类似；最有用的信息我用红色标记，其大意是不能执行上面的2进制或可执行文件。在这个条目中，只有2个执行文件—printf及mail。我把它按原样单独拿出来执行，操作过程如下：

　　（1）/usr/bin/printf  “"%b" "***** Nagios 2.9 *****\n”  输出 ***** Nagios 2.9 *****，这是正常的结果。

　　（2）/bin/mail -s "Host DOWN alert for mail-server!" sery@163.com 输出su: /bin/mail: No such file or directory，没找到路径或目录。前面还手动发了邮件的，明明有mail这个客户端程序呀！可能这个路径不对，是linux的mail路径。查一下freebsd的mail路径，执行find / -name 得到mail在freebsd的路径为/usr/bin/mail 。

　　到这里，我们知道了为啥不能发邮件的根本原因，接下来，我把nagios的配置文件commands.cfg的host-notify-by-email、service-notify-by-email的”/bin/mail”替换为“/usr/bin/mail”。其完整形式为：

　　# 'host-notify-by-email' command definition
define command{
command_name    host-notify-by-email
command_line    /usr/bin/printf "%b" "***** Nagios 2.9 *****\n\nNotification Type: $NOTIFICATIONTYPE$\nHost: $HOSTNAME$\nState: $HOSTSTATE$\nAddress: $HOSTADDRESS$\nInfo: $HOSTOUTPUT$\n\nDate/Time: $LONGDATETIME$\n" | /usr/bin/mail -s "Host $HOSTSTATE$ alert for $HOSTNAME$!" $CONTACTEMAIL$
}
# 'notify-by-email' command definition
define command{
command_name    service-notify-by-email
command_line    /usr/bin/printf "%b" "***** Nagios 2.9 *****\n\nNotification Type: $NOTIFICATIONTYPE$\n\nService: $SERVICEDESC$\nHost: $HOSTALIAS$\nAddress: $HOSTADDRESS$\nState: $SERVICESTATE$\n\nDate/Time: $LONGDATETIME$\n\nAdditional Info:\n\n$SERVICEOUTPUT$" | /usr/bin/mail -s "** $NOTIFICATIONTYPE$ alert - $HOSTALIAS$/$SERVICEDESC$ is $SERVICESTATE$ **" $CONTACTEMAIL$
}

　　修改完配置文件commands.cfg后重启 Nagios，再查看nagios日志，不再有“Make sure the script or binary you are trying to execute actually exists...”报错，并且有发送报警邮件的记录了：

　　[root@nagios /usr/local/nagios/var]# tail -f nagios.log
[1217170467] SERVICE ALERT: mail-server;check_tcp 995;CRITICAL;SOFT;1;CRITICAL - Socket timeout after 10 seconds
[1217170534] Auto-save of retention data completed successfully.
[1217170577] HOST ALERT: mail-server;DOWN;SOFT;1;CRITICAL - Plugin timed out after 10 seconds
[1217170587] HOST ALERT: mail-server;DOWN;SOFT;2;CRITICAL - Plugin timed out after 10 seconds
[1217170597] HOST ALERT: mail-server;DOWN;SOFT;3;CRITICAL - Plugin timed out after 10 seconds
[1217170607] HOST ALERT: mail-server;DOWN;SOFT;4;CRITICAL - Plugin timed out after 10 seconds
[1217170607] HOST ALERT: mail-server;UP;SOFT;5;PING OK - Packet loss = 0%, RTA = 111.63 ms
[1217170607] SERVICE ALERT: mail-server;check_tcp 995;CRITICAL;SOFT;2;CRITICAL - Socket timeout after 10 seconds
[1217170687] SERVICE ALERT: mail-server;check_tcp 995;OK;SOFT;3;TCP OK - 3.137 second response time on port 995
[1217171057] SERVICE NOTIFICATION: sery;fav-0;check_tcp 443;CRITICAL;service-notify-by-email;CRITICAL - Socket timeout after 10 seconds

　　收邮件，迫不及待，哈哈，我的163邮箱收到久违的报警信息了。再回去瞧一眼邮件日志/var/log/malllog,也记录了这个发送情况。

　　经验总结：通过日志记录，对于我们排查故障确实有着不可估量的好处。在实际的工作中，我们应该随时检查系统日志以及应用程序相关的日志，从记录项中寻找蛛丝马迹，从而得出解决问题的方法。