flyinweb's blog

解决Centos5上升级Python后yum不能用的问题

There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:
 
 No module named yum
 
Please install a packagewhich provides this module, or
verify that the module is installed correctly.
 
It's possible that the above module doesn't match the
current version of Python, which is:
2.6.5 (r265:79063, Jul  22010, 16:30:56)[GCC 4.1.2 20080704(Red Hat 4.1.2-46)]If you cannot solve this problem yourself, please go to
the yum faq at:
 http://wiki.linux.duke.edu/YumFaq

htop - an interactive process viewer for Linux

This is htop, an interactive process viewer for Linux. It is a text-mode application (for console or X terminals) and requires ncurses. Tested with Linux 2.4 and 2.6.

官方网站：http://htop.sourceforge.net/
　　可以进行水平或竖直滚动 （总算可以看到所有进程和全部命令行了）
　　可以跟踪进程 （通过集成strace实现）
　　主页面上显示常用功能项，很方便。top里可以要'h'一下。
　　支持进程树状显示
　　可以按名称查找进程
　　支持鼠标
　　htop很不错，但还可以做得更好，下面是我想要的功能：
　　显示进程打开的文件
　　显示进程内存映射情况
　　更完整的man手册（比如设置更新周期的命令行选项'-d'就没有在手册中说明）
　　P.S. strace是个宝贝。单独做一个strace前端本身就是个不错的项目，支持对strace结果的分类，查询等功能。

linux系统上可以使用（centos 2.6.18-144开始支持），dstat版本至少是：dstat-0.6.7-1.rf.noarch.rpm
安装
wget -c http://linux.web.psi.ch/dist/scientific/5/gfa/all/dstat-0.6.7-1.rf.noarch.rpm
rpm -Uvh dstat-0.6.7-1.rf.noarch.rpm

使用
# dstat -M topio -d -M topbio

Newer Linux kernels have per-process I/O accounting and you can use the iotop tool to find out what’s performing I/O, but in many cases I’m trying to find the source of an I/O problem in an older kernel. I found sort of a hack-ish way to do that today, while trying to figure out why a system was basically unresponsive.

I found a post on Stack Overflow that showed a way you can get per process I/O statistics from the kernel even in older kernels. I adapted this to my needs, and wrote a little script.

Mark Wong’s entry titled “Following up a couple questions from the presentation at PSU on January 8, 2009” just caught my eye:

What is ‘iopp’?

It’s a custom tool to go through the Linux process table to get i/o statistics per process. It is open source and can be downloaded from:

http://git.postgresql.org/?p=~markwkm/iopp.git;a=summary

Following are few situations where you may be interested in performing a filesystem benchmarking.

=> Deploying a new application that is very read and write intensive.
=> Purchased a new storage system and would like to measure the performance.
=> Changing the RAID level and would like to measure the performance of the new RAID.
=> Changing the storage parameters and would like to know the performance impact of this change

This article gives you a jumpstart on performing benchmark on filesystem using iozone a free Filesystem Benchmark utility.

系统启动顺序：

加载BIOS的硬件信息
└ 读取MBR的Boot Loader信息 stage1,stage2,grub.conf
└ Boot Loader加载内核 vminux,initrd
└ 内核执行init程序并取得inittab中运行信息
├ init执行/etc/rc.d/rc.sysinit
└ /etc/fstab加载分区等
├ init执行/etc/rc.d/rc
├ 启动对应运行级别的守护进程
└ 最后执行S99local,即/etc/rc.d/rc.local
└ init启动了mingetty，打开了终端供用户登录系统
└ 执行/bin/login程序
└ 成功登陆之后启动shell控制主机
└ shell配置脚本
├ /etc/profile --->/etc/profile.d/*.sh
└ ~user/.bash_profile
└ ~user/.bashrc
└ /etc/bashrc