My new guest VMs under Xen seem to be having issues where upon each reboot, the network interface gets incremented by 1. For instance, it starts at eth0, then goes to eth1, then eth2, and eventually ethX. There are two issues to fix: 1) get the count back to 0, and 2) stop it from counting again.

I was able to get them to decrease by looking in the /etc/udev/rules.d/70-persistent-net.rules file and removing all entries.

Next, I was able to prevent this by simply inserting a MAC address to the interface in the configuration. For instance, one of my domU’s has this entry:

vif         = [ 'mac=00:D0:59:83:DC:B5,bridge=xenbr0' ]

Lastly, I made sure (as I would with any server) to create an entry in the /etc/network/interfaces file.

auto eth0
iface eth0 inet static
address 192.168.1.16
gateway 192.168.1.1
netmask 255.255.255.0

Works like a charm.

One of the biggest things I regret is not utilizing Xen more. I’ve finally been admitted to Amazon’s EC2 Limited Beta, just two days before I leave, so not enough time to actually do anything fun. However, I think Xen is an ideal infrastructure aid for SMEs in particular. The cost of technology is continuing to decrease, which means bigger servers cost less. This is great for the small/branch office. Let me explain.

One of the themes I noticed while studying and taking the MCSE was that the solution to the majority of the problems was to just buy more servers. Even for simple things like DHCP, buy another server. I’ve always operated on a limited budget, and anyways, I don’t think money should be wasted on resources when it isn’t needed. With a VT chipset, you aren’t tied to any OS in particular.

My friend Ian and I were talking and he illustrated a great usage of Xen through his work. What he’s ended up doing is installing the Small Business Edition of Server 2003 in a Xen node. The reasoning is that SBE is, apparently extremely difficult to create backups of – mainly due to odd file locking behavior. I’ve had similar thoughts, but mainly taking advantage of Xen’s migration feature. The idea of taking a small branch office and putting everything on a Xen server is quite appealing to me, especially considering a second server could be used to create virtual hot spare.

As you can see, I like Xen. I’ve found it relatively easy to install, and the fact that it is starting to come bundled with recent distributions is pretty darn, sweet.

We don’t want to have a billion servers each doing their own task – so what can we use as a solution? Server virtualization (or semi-virtualization or para-virtualization). This involves cutting down a server into mini servers that each have full customization. Our VPS at hostmysite is like this. So why would you want to do this? A few reasons actually.

-Localize exploits. Let’s say DNS gets exploited – the access gained would only be for DNS, and not for mail and web and everything else.

-Easy “upgrades,” backups and redundancy. Let’s say we start to use MySQL more and more, but the server can’t handle it. To upgrade (ignoring replication for this example) we could just turn off the virtual server (in essense lock files), move it to other server, drop it into another server that is setup to do virtualization, and turn it it on. Nearly no downtime, and you know it will work.

Anyhow, worth looking at. Here are some of the most mature linux virtualization packages out there:

http://openvz.org/ – This is the open source version of hostmysites VPS. The main difference is it isn’t setup for doing mass hosting (like, 1000 VPSs on a huge mainframe).

http://www.openvps.org/

http://linux-vserver.org/ – Very plain website, but there is news that the authors are pushing for this code to be included in the Linux kernal natively.

http://www.cl.cam.ac.uk/Research/SRG/netos/xen/ – I’ve heard rumors also about this being one of the most advanced.

http://www.vmware.com/ – The one and only. This is full virtualization so will contain the most overhead (some of the previous packages have almost no overhead, not even 1%). Oh yea, and this “costs” money.