flyinweb's blog

It’s probably mod_php, and try recompiling PHP without zend_multibyte. If you have WITH_MULTIBYTE=true in /var/db/ports/php5/options, change it to WITHOUT_MULTIBYTE=true and rebuild the port.

The apache web server has become the predominant web server on the Internet for it's scalability, standards compliance and the numerous features that come bundled with the server. As more and more features are added to apache, and as web applications evolve to meet new demands, bugs will periodically surface in applications and the web server code base itself. Since application and server bugs can lead to service failures and downtime, it is important to have a good set of tools to assist with isolating and locating problems. This article provides an introduction to debugging apache web server problems, and covers several tools and techniques that can help troubleshoot problems when they arise.

Recently I have noticed that my Apache error log file shows it is generating segmentation faults. After doing little research I came to know that there is not simple solution to find of causes of this problem. I got an error that read as follows:

[Mon May 8 11:20:09 2006] [notice] Apache/2 (WebAppBETA) child pid 1256 exit signal Segmentation fault (11)
[Mon May 8 11:23:12 2006] [notice] Apache/2 (WebAppBETA) child pid 1301 exit signal Segmentation fault (11)

The problem is that our application development team has hacked (aka modified source code) Apache 2.0 source tree for application my company developing. To get rid of this problem I was asked to configure a Linux system so that Apache can dump core files on segmentation faults.

Nginx默认是显示版本号的，如：

[root@bkjz ~]# curl -I www.nginx.org
HTTP/1.1 200 OK
Server: nginx/0.8.44
Date: Tue, 13 Jul 2010 14:05:11 GMT
Content-Type: text/html
Content-Length: 8284
Last-Modified: Tue, 13 Jul 2010 12:00:13 GMT
Connection: keep-alive
Keep-Alive: timeout=15
Accept-Ranges: bytes

这样就给人家看到你的服务器nginx版本是0.8.44，前些时间暴出了一些Nginx版本漏洞，就是说有些版本有漏洞，而有些版本没有。这样暴露出来的版本号就容易变成攻击者可利用的信息。所以，从安全的角度来说，隐藏版本号会相对安全些！

一般情况下，软件的漏洞信息和特定版本是相关的，因此，软件的版本号对攻击者来说是很有价值的。

在默认情况下，系统会把Apache版本模块都显示出来（http返回头信息）。如果列举目录的话，会显示域名信息（文件列表正文），如：

[root@localhost conf]# curl -I 192.168.146.188  
HTTP/1.1 200 OK
Date: Tue, 30 Aug 2011 09:17:42 GMT
Server: Apache/2.2.4 (Unix) PHP/5.2.6
Last-Modified: Sat, 20 Nov 2004 20:16:24 GMT
ETag: "be0533-2c-3e9564c23b600"
Accept-Ranges: bytes
Content-Length: 44
Content-Type: text/html

Linux系统出现了性能问题，一般我们可以通过top、iostat、free、vmstat等命令来查看初步定位问题。其中iostat可以给我们提供丰富的IO状态数据。

一. DRBD介绍