Miscellaneous Knowledge

iptables is a common linux software firewall. However, for many new linux users who are unfamiliar with the command line (or google!) some simple tasks such as opening a port on the firewall in order to allow a web-facing service to be reachable by everyone can be daunting.

However, it’s actually quite simple. Just issue the following command;

iptables -I INPUT -p tcp –dport PORT -j ACCEPT

Where PORT is the port number you wish to open, e.g 80. Note that there is a double dash before dport.

The syntax of this command is quite simple. -I INPUT indicates you are altering the input table -p tcp indicates that the protocol is TCP, –dport PORT indicates the destination port and -j accept indicates the action to be taken on matching the rule – in this case to accept traffic. Note that the command requires superuser privileges to execute.

Don’t forget that this will be in vain if iptables isn’t actually running. Under CentOS, you can start the iptables service by issuing the command service iptables start. You’ll also need to save the iptables rules if you want them to persist across a reboot, under CentOS you can issue the command /sbin/service iptables save to achieve this.

Ever felt like trying out the KDE desktop interface, but didn’t fancy downloading Kubuntu and installing from scratch? Good news! You can easily install KDE from your current Gnome-based Ubuntu install and it’s dead simple.

Open up Synaptic Package Manager and search for “kubuntu” in the quick search, in the list of results select kubuntu-desktop and then click apply. Synaptic will then download and install all the files for KDE.

However, how do you switch to KDE from Gnome once it’s installed? Simply log out and then click your username as usual, at the bottom of your screen click Session and select KDE and then log in as normal. This time, instead of Gnome you’ll get the KDE desktop interface. If you want to switch back to Gnome just log out and select Gnome under session.

Now you can try out a new desktop interface without going through a lot of hassle.