Setting up a CentOS 6.3 Virtual Host

This guide outlines how I set-up my virtual host using CentOS 6.3 (a free release version of Red Hat Linux with all the branding removed). It's partially based on my previous installation guide. I also used my guide to create a bootable USB installation disk, but this guide should work equally well with the standard DVD install.

Installation

1. Boot up your installation media (you may need to edit your BIOS to do so)
2. Select 'Install or upgrade an existing system' from the menu
3. Select your language and keyboard layout.
4. Click next at the splash screen.
5. Choose the 'Basic Storage Device' option
6. Select the 'Fresh Installation' option
7. Enter in the host-name of your new server (for best results you should append your domain name to the end so it works seamlessly with SSL certificates) i.e. testserver.example.com
   
   If you want to configure a static IP address click on the 'Configure Network' button, select the your network card (probably eth0) and enter away.
   
   If you are going to use DHCP, or just don't know, just hit 'Next'
8. Select the correct timezone for you (just click a location on the map and it should select the closest one to you).
9. Enter in an appropriate root password. Make as long and complex as possible (long sentences with mixed character types are easier to remember than jibberish strings; for instance 'My office is situated in 1234 fake street, Fakeville!')
10. In this example we are going to go for a custom partition layout, so select 'Create Custom Layout'. If you are fine with defaults, just skip to part .
11. Delete all existing partitions and do the following:
• A /boot partition of about 100MB. Use the ext4 format


• Create a LVM Physical Volume that fills up the rest of the hard-drive


• Create a LVM Volume Group with a Physical Extent of 4MB.


• Create LVM Logical Volumes on the Volume group as follows (make sure you leave some free space for your Virtual machines!!):


• Swap space that is at least equal to how much RAM is in your server
• /tmp/ should be as big as the largest file you will be manipulating (for instance, if you are copying a DVD you will need at least 4GB)
•  /var/log and /var/log/audit are separated so that if your log system goes haywire it does not kill the space for other applications. Dedicate a couple of gigabytes to each.
• /home/ and /usr/ should be a few gigabytes each. /usr/ just holds your applications and should remain pretty static, while /home/ is where you will store your personal files.
• /var/ and /var/www/ will contain the majority of space on your system. MySQL stores your database files in /var/lib/mysql/, while Apache runs from /var/www/. Dedicate adequate space to each folder.
• Your root folder (/) will only need a few GB of space. It will mainly hold configuration files.
12. The system will take some time to format your hard-drive. Once it is complete it will ask you to install the boot-loader. While the defaults are suitable, for extra security you should consider password protecting your boot-loader.
13. We can now select our packages. You can customize the system to suit your needs, but for the basics just select 'Basic Server' from the menu and the 'Customize now' from the radio buttons. Hit 'Next'.
14. Do the following edits:
• Remove the 'Java Platform' and 'Directory Client' meta-packages
• Add all of the Virtualization meta-packages (including client, platform and tools)
• Because the virt-manager tool requires a GUI, you may need to install the 'X Windows System'  and the 'KDE Desktop'
• From the base system, I removed packages such as hunspell and word (as well as hardware tools like RAID that I was not using)
15. Reboot your system!

 House cleaning

I suggest you take this time to tighten up your machine; run updates, turn off services, install software and harden your machine. You should also consider setting up your SSH settings.

Have a look at some of my guide to Software package integrity checks (aide).

Creating our first guest

We are going to use LVM based guests, so if you haven't left any space on your LVM partition I suggest you use these guides to free up some space. If you have partitions you don't think you need anymore, just delete it.

You may also want to ensure that KVM is installed so that you get the benefit from it's kernel and hardware virtualisation.

yum install kvm qemu-kvm qemu-kvm-tools

Now you just need to create a logical partition in the volume to store your VM by running the following command (assuming your volume is call VolGroup):

lvcreate -L20G -n vm1 VolGroup

To install to this new partition, just run the following command:

virt-install --connect qemu:///system -n vm1 -r 512 --vcpus=2 --disk path=/dev/VolGroup/lv_vm1 -c /path/to/installation.iso --graphics vnc --noautoconsole --os-type linux --os-variant rhel6

Note the following parameters:

• -r specifies the RAM size
• --vcpus specifies the virtual CPU's to use
• --os-type helps to optimise the VM by specifying an operating system
• --os-variant is a optional parameter, but helps further optimisation of the emulator.

Further reading

• This excellent series from 'How to forge'. Part 1 (Configuration), Part 2 (Connecting to Guest), Part 3 (Creating Guest with GUI), Part 4 (Command line tools), and Part 5 (LVM based guests).
• CentOS documentation on using virt-install
• This excellent guide by Blog Normation
• A beginners guide to LVM from How to Forge