Monthly Archives: November 2013

Turn On Linux Servers Remotely Without Physical Access

Wakeonlan enables you to switch ON remote servers without physically accessing it. Wakeonlan sends magic packets to wake-on-LAN enabled Ethernet adapters and motherboards to switch on remote computers. By mistake, when you shutdown a system instead of rebooting, you can … Continue reading

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SSH hardening on Linux Servers

While allowing ssh connections to the production servers there are few best practices which a sysadmin must know.These are explained in this article. Openssh options are controlled through the /etc/ssh/sshd_config file. Options that uses the default values, the sshd_config file … Continue reading

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How to know Size and Name of all Installed rpm

If you want to know the size and name of all the rpm’s that are installed on your system then use the following command : #rpm -qia|awk ‘$1==”Name” { n=$3} $1==”Size” {s=$3} $1==”Description” {print s  ” ” n }’ |sort … Continue reading

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How to Increase Resolution for Ubuntu or Linux in Virtualbox

When a new Virtual Machine, or Virtual PC, is setup in Virtualbox for Ubuntu, or another Linux flavor, the screen size and screen resolution may be fixed smaller than your maximum resolution setting. This problem can be fixed by installing … Continue reading

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How to Identify main traffic sources in Linux

Use this command to get rid of All the hosts using web server. #netstat -natp | grep :80 | awk ‘{print $5}’ | cut -d: -f1 | sort | uniq -c | sort -n | tail Output:      25 … Continue reading

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How DHCP Server Works?

DHCP stands for Dynamic Host Configuration Protocol and is used to automatically assign IP configuration to hosts connecting to a network. The Dynamic Host Configuration Protocol (DHCP) provides a framework for passing configuration information to hosts on a TCPIP network. … Continue reading

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How to move Iptables logs to user defined log file.

Iptables logs are generated in /var/log/messages, so its getting difficult to check other messages from /var/log/messages as iptables generates a huge bulk of logs. For moving iptables log to different directory, we have to do changes in following configuration files. 1.) … Continue reading

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How to configure syslog server in redhat linux.

Centralized log server (syslog server) Suppose we have a server and 5 client machines. And we want to monitor the logs of all those client machines. In situations like this, we will use centralized server as a log server. Whatever … Continue reading

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How to find Java Character Set/Encoding in Linux

If you want to know about Character set used by Java on Linux Server then follow the following Steps: 1.) Create a file named as CharacterEncodingExample.java. 2.) Copy & Paste the code to new created file. 3.) Compile Java source code … Continue reading

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How to disable an user account in Linux

What is the correct way to disable all remote access to an account. Clearly, “passwd -l” (and by the same token, “usermod -L”) is insufficient because that will not impact authentication by SSH public key (or other PAM modules other … Continue reading

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How to download updates using yum without installing them

Updates can be downloaded using yum downloadonly plugin without actually installing them to the system. Below steps can be followed for that. Install yum-downloadonly package-name. # yum install yum-downloadonly Create a directory to download packages to. # mkdir /tmp/download Run … Continue reading

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How to Integrate SONAR with Hudson

What is SONAR ? SONAR is code reviewing tool. SONAR needs to be integrated with Hudson so that whenever someone check-in code, then it will be reviewed by SONAR before making a build. Hudson provides a plugin for SONAR and we … Continue reading

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How to Read MySQL Binary Log Files (BinLog) with mysqlbinlog

MySQL database server generates binary log files for every transaction to the databases, provided administrator does not disable or comment out the “log-bin” parameter in my.cny configuration file. The binary log files are written in binary format. Although the binary … Continue reading

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Squid Transparent Proxy Server

A proxy server is a server  that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, … Continue reading

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How to log output of remote ssh session ?

There are many instances when you are going to ssh to remote server for troubleshooting and data gathering purposes and you want to save those data in your computer. There is a useful “tee” command which could be used to … Continue reading

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Network Bonding or Nic Teaming or Link Aggregation in Linux

Link aggregation or trunking or link bundling or Ethernet/network/NIC bonding or NIC teaming are computer networking terms to describe various methods of combining (aggregating) multiple network connections in parallel to increase throughput beyond what a single connection could sustain, and … Continue reading

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How to block ping on Linux Servers

If you want to block ping requests to your critical linux servers due to security concerns then do the following: Edit the file /etc/sysctl.conf [root@server~]# vim /etc/sysctl.conf and look for this line: net.ipv4.icmp_echo_ignore_all and set its value qual to 1 … Continue reading

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Configuring poptop VPN Server in RHEL-5

First of all install all the required Libraries and pptd Server on Linux System. You can also make the use of yum to install the pptp server as… [root@server~]# yum -y install ppp* Now open the file /etc/pptpd.conf. [root@server~]# vim … Continue reading

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Kernel panic – not syncing: Attempted to kill init! ” Error

If you get kernel panic after system reboot…dont panic just follow the steps as shown below : 1. Once you are at the grub screen, press c for command line. 2. On command line execute the following commands. find /grub/stage2 … Continue reading

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