WARNING: outdated instructions
those instructions are not the canonical install instructions and are outdated. You should follow the canonical instructions in INSTALL.txt from now on (which include the use of a more resilient, multiplatform and generic install script.
The rest of this document is kept for posterity.
The easiest way to install Aegir is by using the Shell Install Script that has been developed. Here are the steps to take
Setup the Server
Set up a brand new Linux server, to which you have shell access as the root user. You don't need to install Apache, MySQL or PHP or many of the other steps in Prepare your Server for Aegir - because the script does all of this. However, it doesn't matter if you already have these installed.
Get the Install Script
The install script can be found at: http://cvs.drupal.org/viewvc.py/drupal/contributions/profiles/hostmaster....
This can be downloaded with CVS using the following command :
cvs -z6 -d:pserver:anonymous:anonymous@cvs.drupal.org:/cvs/drupal-contrib checkout contributions/profiles/hostmaster/install.sh.txtYou can then rename and upload it to your server, or you can copy it from the browser window, go to your shell session on the server, type vim install.sh and then paste it in (type 'i', then right click the mouse).
Run the Install Script
You must be root to run the install script or it won't run. As root, simply type
./install.sh
On some server setups this may not work, and you'll need to type:
sh install.sh
Follow the Instructions
The install script then walks you through the installation process, and is very clear in its instructions. You simply need to input what it asks, and do what it says!
At the end of this you'll have a working Aegir installation.
You should now take some basic security steps to harden your server, such as enabling a firewall etc. Read a bit about this at http://groups.drupal.org/node/25482.
Now you can follow the steps at Aegir Is Installed - What Next?