Linux Screen Shortcuts

Screen is a much under utilised program, which provides the following functionality:

  • Remote terminal session management (detaching or sharing terminal sessions)
  • unlimited windows (unlike the hard-coded number of Linux virtual consoles)
  • Scroll back buffer (not limited to video memory like Linux virtual consoles)
  • copy/paste between windows

Postfix OpenLDAP Courier-imap Amavisd-new SpamAssassin and clamav HowTo

This is a step by step guide on how to configure GNU/Linux system with Postfix, OpenLDAP, Courier-imap, Amavisd-new, SpamAssassin and clamav. Even though this setup was configured on Centos 5, with minor tweaks you should get it working on any GNU/Linux distribution.

Building necessary software

Apache connections dropped by Haproxy

Many times on RHEL, haproxy is not reliable it gives an errors while connecting to apache backend, at that time it logs the following errors into /var/log/messages

kernel: ip_conntrack: table full, dropping packet

this is related to ip_conntrack kernel module.

If found this error message into /var/log/messages need to apply following steps

ip_conntrack_max table full dropping packets

If you notice the above message in syslog, it looks like the conntrack database doesn’t have enough entries for your environment. Connection tracking by default handles up to a certain number of simultaneous connections. This number is dependent on you system’s maximum memory size.

Some symptoms can be:

Running Tomcat as Service

In previous post we have setup Tomcat to run its multiple instances now we want that tomcat should start automatically on server reboots. This can be achieved by adding tomcat service script.

Introduction

This document will teach us how to setup Tomcat to run as a service (startup when booted) on Linux.