I mentioned last time that Citrix Xen Server was incredibly fast and easy to setup, but a bit of a pain to use, practically, because the Centos VM I created on it insisted on running in strictly command-line mode only. All true enough… but a GUI is do-able, and here’s how I did it.

First, I read the available documentation! The relevant bit is here, which references a bit about installing guest agent software, which is documented here.

The basic outcome is that, in console (text) mode, you install the Xen Agent software for VM Guests first (that’s into the Centos 5.3 x64 virtual machine I’d already built in text mode, of course). You do that by logging on as root at the console, switching  the DVD selector so that it reads xs-tools.iso and then typing the commandmount /dev/xvdd /mnt. You’ve just effectively inserted the Xen Tools CD into your virtual CD-ROM.So now you can launch the relevant installer off that virtual CD by typing the command /mnt/Linux/install.sh. Say ‘yes’ when prompted and then reboot the virtual PC.

Next, you need to edit the Centos virtual machine’s /etc/gdm/custom.conf file (remember, I only deal with Centos 5.3 these days: the file is different for Centos 3 and 4 versions). I edited that file to contain the following:

The [servers] bit is already in the file, but everything else has to be typed in, using your favourite text editor (nano in my case). The command= line continues without a break all the way through to the end -BlacklistTimeout 0 bit. The ‘flexible=true’ stuff is a new line in its own right.

With that file changed and saved, I then had to switch off the Centos firewall -something I’d normally do automatically in a GUI OS install, because the installer prompts you. But in a CLI environment, you have to take that step yourself. Logged in as root, type the command system-config-securitylevel-tui and -using your skill and judgement- press whatever combination of TAB, Space Bar and ENTER switches off the firewall in its entirety. You should also set SELinux to at least permissive if not outright disabled (because Oracle doesn’t interact with SELinux very well). Note that if you set SELinux to disabled, you should reboot the VM so that the new setting can take effect. If you set it to permissive, a reboot is not required.

Finally, you can now launch the Gnome Desktop Manager by simply typing the command gdm. If for some reason it’s already running. just ype  /usr/sbin/gdm-restart instead. In either case, you should see the Switch to Graphical Console button light up in the Xen Management tool on your Windows client PC. Click that, and you’ll be rewarded with  graphical Centos login screen -and a short while later, the glory that is this:

You will note from that screenshot that I’m busy running the Goal script for automated Oracle installations… which gives you a clue that Oracle on-Centos-on-Xen is a piece of cake. And which might, I suppose, be the subject of another post or several in the coming days! (It completes in 19 minutes, which as these things go is pretty darn’d quick, and very close to physical PC installation times. Impressive).

I have to say as a parting note that it’s a shame that Citrix Xen makes having a graphical Centos experience a matter of editing a couple of textfiles and keeping your fingers crossed. But I cannot fault the fact that it is a matter of typing just one or two commands and then the pain is behind you. Given the capability of this software, and its extraordinary price of US$0.00, I can live with it -especially as there are so many other redeeming features!

Tags: Centos, Virtualisation, Xen
This entry was posted on Wednesday, October 7th, 2009 at 7:39 pm and is filed under Linux configuration, Virtualisation. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.