Admins eHow SysAdmin Tips & Tricks

March 28, 2011

Cracking the credit card code

Filed under: General — admin @ 7:08 am

If you think Credit Card number is something random , then you are quite wrong. every number in a credit card is meaningful.

How to fix “Starting httpd: httpd: apr_sockaddr_info_get() failed”

Filed under: Apache,General,linux — Tags: , — admin @ 5:49 am

This error is caused by the improper configuration of hostname of server. to fix it follow the steps below :
Change HOST.DOMAIN.com to your own hostname.

echo HOST.DOMAIN.com > /etc/hostname
/bin/hostname -F /etc/hostname
/etc/init.d/httpd restart

October 14, 2010

Ping Scan IP Range Using nmap

Filed under: General,Security — Tags: , , , , , — admin @ 1:11 am

You can use nmap to ping scan IP ranges , by following commands :

nmap -sP 192.168.1.0/24

or

nmap -sP 192.168.1.1-254

October 7, 2010

PayPal Link Generator – Build your own 1 click payment links

Filed under: General — Tags: , , — admin @ 3:20 pm

Your PayPal E-mail:
Description:
Amount: USD

July 31, 2010

Manual WideScreen resolution for WarCraft 3

Filed under: General — Tags: , , , , , , , — admin @ 11:34 am

WarCraft 3 doesn’t support many new wide screen resolutions , you can use the following program to manually set WarCraft 3 resolution.
Download : WarCraft 3 Manual Resolution

July 28, 2010

Hamachi Alternatives quick list

Filed under: General — Tags: , , , , , , — admin @ 9:36 pm

Here is a quick list of Hamachi ( zero-configuration virtual private network (VPN) ) alternatives :
tinc : http://www.tinc-vpn.org
gbridge : http://www.gbridge.com/
socialvpn : http://socialvpn.wordpress.com/
remobo : http://www.remobo.com/
wippien : http://www.wippien.com/
n2n : http://www.ntop.org/n2n/
tunngle : http://www.tunngle.net/en/
comodo easy vpn : http://easy-vpn.comodo.com/

July 16, 2010

How to install Byte UnixBench on debian lenny

Filed under: Debian,General — Tags: , , , , , , — admin @ 2:28 pm

From UnixBench website :

UnixBench is the original BYTE UNIX benchmark suite, updated and revised by many people over the years.

The purpose of UnixBench is to provide a basic indicator of the performance of a Unix-like system; hence, multiple tests are used to test various aspects of the system’s performance. These test results are then compared to the scores from a baseline system to produce an index value, which is generally easier to handle than the raw scores. The entire set of index values is then combined to make an overall index for the system.

Some very simple graphics tests are included to measure the 2D and 3D graphics performance of the system.

Multi-CPU systems are handled. If your system has multiple CPUs, the default behaviour is to run the selected tests twice — once with one copy of each test program running at a time, and once with N copies, where N is the number of CPUs. This is designed to allow you to assess:

  • the performance of your system when running a single task
  • the performance of your system when running multiple tasks
  • the gain from your system’s implementation of parallel processing

Do be aware that this is a system benchmark, not a CPU, RAM or disk benchmark. The results will depend not only on your hardware, but on your operating system, libraries, and even compiler.

First install required libraries for compilation :

apt-get install libx11-dev libgl1-mesa-dev libxext-dev perl  perl-modules make

Then get the unixbench and run it :

wget http://byte-unixbench.googlecode.com/files/unixbench-5.1.2.tar.gz
tar zxvf unixbench-5.1.2.tar.gz
cd unixbench-5.1.2
./Run

April 30, 2010

Connect to PPTP VPN from Linux only by one command

Filed under: CentOS,Debian,General — Tags: , , , , , , , , , — admin @ 1:03 pm

I’ve used this method to connect to a windows PPTP VPN server on PCLinuxOS 2010 , but I am sure it will work on other ditros too.
First make sure sure pptp-linux and ppp packages are installed on your client PC.
you may install them by yum or apt-get or package manager of your linux.
then use the following command to connect to VPN.

pppd pty "pptp IP_OR_FQDN_VPN_SERVER --nolaunchpppd" file /etc/ppp/options.pptp user USERNAME password PASSWORD

replace IP_OR_FQDN_VPN_SERVER with IP or DNS of your VPS server.
replace USERNAME with your VPN username.
replace PASSWORD with your VPN password.
wait for like 10-15 seconds , then run ifconfig command , you should see ppp0 interface there , if it is not there , you can troubleshoot by looking into syslog of your linux.
please note this command is good for connecting to a windows VPN server with default configuration , if you have any custom settings , you may need to edit /etc/ppp/options.pptp file.
to disconnect form VPN , use the following command :

killall pppd

if you need to route all of your traffic to VPN server ( use it as a gateway ) , do the following :
create a file named vpn-up in /etc/ppp/ip-up.d and put the following lines inside it :

#!/bin/bash
H=`ps aux | grep 'pppd pty' | grep -v grep | awk '{print $14}'`
DG=`route -n | grep UG | awk '{print $2}'`
DEV=`route -n | grep UG | awk '{print $8}'`
route add -host $H gw $DG dev $DEV
route del default $DEV
route add default dev ppp0

and make it executable by :

chmod +x vpn-up

create another file named vpn-down in /etc/ppp/ip-down.d and put the following lines inside it :

#!/bin/bash
H=`route -n | grep UGH | awk '{print $1}'`
DG=`route -n | grep UGH | awk '{print $2}'`
DEV=`route -n | grep UGH | awk '{print $8}'`
route del -host $H
route add default gw $DG dev $DEV

and make it executable by :

chmod +x vpn-down

now reconnect to VPN , and your routing will be done automatically.

April 25, 2010

Block port 25 in Routing and Remote Access (RAS) to prevent spam

Filed under: General — admin @ 9:05 am

If you have a VPN server running on windows using routing and remote access , some of your users may abuse your VPN service by sending spam emails from your IP.
in order to prevent it , you need to block outgoing port 25 ( SMTP ). here is an illustrated guide on how to do it in RAS :

Excellent windows dump file analyzer

Filed under: General — Tags: , , , , , , , , , — admin @ 8:53 am

Today I had a BSOD ( Blue Screen Of Death ) on one of my windows servers and after searching the net , I found an invaluable tool which can simplify analyzing the dump file generated by windows after the crash to find out the root cause of crash.
This tool is a must have for every windows system administrator , for more information visit the following link :
WhoCrashed Comprehensible Crash Dump Analyzer

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