Thursday, March 29, 2012

Ubuntu on Lion under VirtualBox (4)

The VirtualBox docs (Chapter 6) discuss several networking modes. The default is NAT

Network Address Translation (NAT)
If all you want is to browse the Web, download files and view e-mail inside the guest, then this default mode should be sufficient for you, and you can safely skip the rest of this section. Please note that there are certain limitations when using Windows file sharing (see the section called “NAT limitations” for details).

Bridged networking
This is for more advanced networking needs such as network simulations and running servers in a guest. When enabled, VirtualBox connects to one of your installed network cards and exchanges network packets directly, circumventing your host operating system's network stack.

I've done what we're about to do (serve pages to the host) using NAT, and I thought I had it all figured out (e.g. this post). But even though it was working yesterday, it's not working today, and I've tried everything I can think of. So, we'll leave that aside and go with "bridged" mode, noting also that this is what the docs recommend (above).

There are three steps to set it up. In VirtualBox Manager, select the correct VM and click on Settings, then Network. As shown in the screenshot, we want Bridged Adaptor.


Make a note of the Mac Address, this changes every time you change the setting. Currently it's 08:00:27:41:a6:2c.

The second step is to configure the DHCP server (on my Airport) using Airport Utilities. We want to reserve a particular IP address for the VM.



And the final step is to configure networking in Ubuntu to use manual IP address assignment. Under Networking > Edit Connections you'll see this:


The VM acts like it's wired. Under Wired edit Wired connection 1 to give IPv4 Settings as shown.


That's it.

[UPDATE: In the screenshot, you'll see that the DNS server is not specified. We need to do that. Enter 10.0.1.1 ]

Now restart the server and from Terminal in OS X do:

> curl http://10.0.1.2:8080/cgi-bin/test.py
<head></head>
HTTP_ACCEPT */* 
HTTP_USER_AGENT curl/7.21.4 (universal-apple-darwin11.0) libcurl/7.21.4 OpenSSL/0.9.8r zlib/1.2.5 
SERVER_NAME 10.0.1.2 
REMOTE_ADDR 10.0.1.3 
SERVER_PROTOCOL HTTP/1.1 
SCRIPT_FILENAME /usr/lib/cgi-bin/test.py 
..

A note about the port we're using. As the VirtualBox docs say:

On Unix-based hosts (e.g. Linux, Solaris, Mac OS X) it is not possible to bind to ports below 1024 from applications that are not run by root.
An interesting discussion of why this limitation persists can be found here.

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