I recently upgraded to Linux Mint 14 “nadia”, which is based on Ubuntu 12.10. I use dnsmasq as a local DHCP server and DNS resolver for virtual machines. Installing dnsmasq on Linux Mint 14 broke host DNS resolution. The issue is easily reproducible: stop dnsmasq, DNS stops working. Start dnsmasq, and it works again.
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Time marches on, and so do all those little changes in Linux distribution releases. Most of my really popular blog posts are how-to guides on complicated-but-useful procedures for the technical Linux user. Those users are the same ones who may read the date in the URL and say “Ewww, this was written three years ago, it must be totally outdated now!” I’ve decided to update the most popular posts to bring them up to date. This post is “Using host networking and NAT with VirtualBox“, version 2.0.
I try to post a few times each month, but somehow January (and most of February) fell through the cracks. Lately I’ve been busy with operational tasks, which hasn’t left me much room for engineering. I haven’t solved any particularly hard or unusual problems, which is usually what I write about. Instead, I’ll write about a routine problem that is nonetheless tricky enough to warrant discussion.
Most of the time I’m not in the same country as the servers I administer. Which means I can’t just drive down and fix something when it goes wrong. It also means that making changes to the network is particularly dangerous. So is updating the kernel, initrd, or GRUB configuration. It is possible to leave a server in a state that requires you to be physically present to fix it. I call this kind of work “flying without a net”. Here are my techniques for safely working without console access.
We run several virtual machine host servers on a network with multiple VLANs. The virtual machines are members of different VLANs, but are not themselves aware of the VLAN. This is how we did it.
Since upgrading to Ubuntu 9.10 I’ve noticed poor performance of VirtualBox guests with Intel VT-X hardware virtualisation enabled. This has been noted in a few places, but I didn’t enable VT-x until recently so I can’t be sure that the problem began with Karmic. I can be sure that it is happening to me now.
Update 2012-05-16: These instructions have been superseded by a new version of this guide. Follow that document instead.
Update 2010-08-18: These instructions are still valid as of VirtualBox 3.2.8 and Ubuntu 10.04 “Lucid Lynx”. VirtualBox now creates a “vboxnet0″ interface by default, but this is not a bridge.
I use VirtualBox every day. The satellite world is infested with bad Windows-based management tools that fail to run in Wine. So I often run those apps in a Windows virtual machine, safely sandboxed the way Windows belongs.
Note to hardware developers: if your network-based device does not have a standards-compliant HTTP interface, you lose. If it has a Windows-based management tool instead, you lose twice. I will buy your product only if I have no other choice.
I imagine running Windows apps is what 90% of VirtualBox users use it for, but it can do so much more than that. I also run several Linux-based VMs, and use them to test server configs, or even whole networks before rolling out the real thing. If you do this, you probably want to use more than the basic NAT networking that VirtualBox uses by default. For instance, wouldn’t it be nice to install an SSH server in the VM, minimise the VirtualBox GUI, and SSH in from a terminal just like you would a real server?