By default, VirtualBox only allows to install 32 bit OS on it. But sometimes, 64 bit OS is wanted for specific uses such as running platform specific tests. To allow installing 64 bit OS on VirtualBox. Below information is needed.Here is the official documentation about 64 bit OS:VirtualBox supports 64-bit guest operating systems, even on 32-bit host operating systems, provided that the following conditions are met:You need a 64-bit processor with hardware virtualization support (see the section called “Hardware vs. software virtualization”).You must enable hardware virtualization ...

These two days, I am building a website and deploying it on a VPS server which uses CentOS 5. I don't have cPanel or Plesk for my account, so I need to install and configure everything myself including Apache, PHP, MySQL and FTP server, also today's topic cron job. Since my website has a ranking algorithm to calculate the rankings of each link and update the ranking on database and I need to calculate the rankings every 5 minutes, so I think to use cron jobs. Here are what I have done which may help you.First we need to understand the crontab commands, it can have different options with this c...

As a system administrator or network engineer or application developer, there is a need to check whether a port on remote server is open so that you can tell whether the service under check is running or not. In this post, we would cover a few methods to check whether a remote server port is open or not on Linux.telnettelnet is the most frequently used command on both Windows and Linux to check port. The simple usage for this command is telnet [host] [port]When the port is open, the output will be like:Trying 192.168.56.160...Connected to 192.168.56.160.Escape character is '^]'.SSH-2.0-Op...

Last week I was generating a MD5 sum for an virtual machine image on one OpenNebula server:# ls -l test.img-rw-r--r-- 1 root root 10486808576 Oct 12 02:21 test.img# md5sum test.imgAt the same time I was clearing the files on the server on another terminal and deleted the above image file mistakenly with :# rm test.imgSince this image file is 10GB, it took some time to remove this file from the server, so I used the Ctrl+Z command to suspend the remove command.[1]+ Stopped md5sum test.imgBy doing this, we can recover the deleted image file later. The rationale here is if other ...

Summary: Mark Shuttleworth says yes, Ubuntu is now competitive with Red Hat Enterprise Linux in the enterprise space. Since last summer, Ubuntu has been more popular than Red Hat as a Web server.When you think of Ubuntu Linux, what do you think of? I would guess you think about the Linux desktop. While Ubuntu is certainly a big player—maybe the biggest—when it comes to the Linux desktop, Mark Shuttleworth, founder of Canonical, the company behind Ubuntu wants you to know that “A remarkable thing happened this year: companies started ...

There are many open source server monitoring software such as cacti and nagios. Besides these, can we write our own shell scripts to monitor them? The shell scripts written by ourselves can fulfill our special requirements better and have a more detailed coverage.Below are some commonly used shell scripts used by Evangelist, an Oracle DBA. 1. Check network gateway traffic#!/bin/bash#network#Mike.Xuwhile : ; do time='date +%m"-"%d" "%k":"%M' day='date +%m"-"%d' rx_before='ifconfig eth0|sed -n "8"p|awk '{print $2}'|cut -c7-' tx_before='ifconfig eth0|sed -n "8"p|awk '{print $6...

To work on Linux platform, you cannot avoid using shell commands to complete some tasks. These tasks can be as simple as list files in some directories or find some text in some file, or can be as complex as monitoring processes. In this post, we will share 37 powerful Linux shell commands. TaskCommands1Delete file with 0 byte(empty file)find . -type f -size 0 -exec rm -rf {} \;find . type f -size 0 -delete2Check process memory consumptionps -e -o "%C : %p : %z : %a"|sort -k5 -nr3Check process CPU utilizetionps -e -o "%C : %p : %z : %a"|sort -nr4Print URLs in cachegrep -r -a jpg /data/cac...

When working on Linux Bash, sometimes there is need to create temporary file. A common way of creating temp file on Linux is creating some file in /tmp directory. However there is security risk when creating temp file in /tmp directory. This post will show how to securely create temp file in Linux Bash.When creating file in /tmp directory, there are some security risks. This directory can be accessed by any user on the system, any user can write data into this directory as well. The files created in this directory can also be read by other users. pike@DESKTOP-G352RBR:/tmp$ touch /tmp/info...