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Update CentOS 4 to CentOS 5 remotely

December 31st, 2009

I just successfully updated my Dell PowerEdge 1850 from CentOS 4.8 to CentOS 5.4, luckily the issues I faced were not so rare. The steps I used are listed below, may it helpful for you as well! Although this post is mainly intended for CentOS it should work on RHEL systems as well.

Before you start, A word of advice i believe most experienced RHEL/CentOS users will show you regarding what you’re thinking:

Upgrade between minor versions (i.e. CentOS 5.2 -> 5.3 -> 5.4, or even 5.0 -> 5.4) YES
Upgrade between major system versions (i.e. CentOS 4.8 to CentOS 5.4) NO » Read more: Update CentOS 4 to CentOS 5 remotely

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Posted in Cmd Reviews, System Tuning

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Explained Awk1line and Sed1line

December 13th, 2009

If you have ever been interested in awk and sed Unix commands, then you probably know about the awk1line.txt and sed1line.txt files that are floating around the Internet. Each file contains around 80 idiomatic sed and awk one-liners for performing various text modification tasks. » Read more: Explained Awk1line and Sed1line

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Posted in Cmd Reviews, Script language

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Install Dell OMSA on Redhat Enterprise Linux

November 19th, 2009

Here we listed 3 ways on the installation of Dell OpenManage Server Administrator on a Redhat Enterprise Linux, you can follows these steps on CentOS or SLES 10, they would work well.

1, Install from RPM packages
Generally we need these RPM packages, you can search and download them from Google.com.
» Read more: Install Dell OMSA on Redhat Enterprise Linux

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Posted in Cmd Reviews, Hardwares, System Tuning

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Hpasmcli Usage Example on ProLiant DL380

November 16th, 2009

Hpasmcli is short for HP System Health Application and Insight Management Agents, it’s a scriptable command line interface for interacting with the hpasm management daemons, which can be used to view / set / modify BIOS settings such as hyper-threading, boot sequence control, and UID LEDs. It can also be used to display hardware status.

In addition to the command line interface, hpasmcli is also usable for incorporating into shell scripts. The return value of hpasmcli can be used to verify a command executed successfully. » Read more: Hpasmcli Usage Example on ProLiant DL380

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Posted in Cmd Reviews, Hardwares

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Prepare the RPM Building Environment

November 9th, 2009

Some days ago, I posted some examples on the common usage of RPM. Now, this post describes a manual preparation of a RPM building environment. With the help of this environment, you can generate upated RPM packages and patch your RPM-based system from source code.
» Read more: Prepare the RPM Building Environment

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Posted in Cmd Reviews, Security

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Basic understanding of the DD command

November 7th, 2009

The DD command we mentioned here is part of the GNU File Utilities.  It’s one of the original Unix utilities and should be in everyone’s toolbox. It’s widely used to write disk headers, boot records, and similar system data areas. Misuse of dd has probably trashed many hard disks and file systems.

Like most well-behaved commands, dd reads from its standard input and writes to its standard output, unless a command line specification has been given. » Read more: Basic understanding of the DD command

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Posted in Cmd Reviews

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Create additional loop devices in Linux

October 27th, 2009

In Unix-like operating systems, Loop device is a pseudo-device that makes a file accessible as a block device. When you mount a file as partition, it would use one loopback device.

I faced a loop device related issue this morning, that’s why I create this article to share some ways to bypass limitation of the loop devices in Linux. » Read more: Create additional loop devices in Linux

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Posted in Cmd Reviews, System Tuning

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Use cpulimit to limit CPU time for process

October 25th, 2009

How we can limit the CPU usage of a sepcified process with the CPUlimit utility?

Cpulimit is a simple program that attempts to limit the CPU usage of a process. It’s expressed in percentage, not in cpu time.

This is useful to control batch jobs, when you don’t want them to eat too much CPU resource. It does not act on the nice value or other scheduling priority stuff, but on the real CPU usage. Also, it is able to adapt itself to the overall system load, dynamically and quickly. » Read more: Use cpulimit to limit CPU time for process

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Posted in Cmd Reviews, System Tuning

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Avoid script running multiple times by file lock

October 22nd, 2009

Sometimes we need a single instance of a script to run at a time. Meaning, the script itself should detects whether any instances of himself are still running and act accordingly.

When multiple instances of one script running, it’s easy to cause problems. I’ve ever seen that about 350 instances of a status checking script running there without doing anything, but eat lots of system resource.
» Read more: Avoid script running multiple times by file lock

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Posted in Cmd Reviews, Programming

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Tips and Tricks on Google Search

October 10th, 2009

With the help of these Google search tips, we mostly can save a lot of time, and gain more informations from the world. It’s especially useful for heavy Google users like me. My Google search History indicates that I raise more than 20 searches on a daily basis.

This article would give us a list on google search tips and tricks. the original version is available here, and I have modified it so that it would be more specific and informative, especially for us technical users. » Read more: Tips and Tricks on Google Search

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Posted in Cmd Reviews, System Tuning

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