Getting Vyatta installed
In my case, getting Vyatta installed was a bit more complicated than it might be for most. Vyatta is distributed in a few different formats, including a Live CD image that you can burn to a disc and a ready-made VMware appliance. Unfortunately, I'm not using VMware, and the box I wanted to install Vyatta on doesn't have a CD-ROM.
However, it's fairly easy to slap together an installer that will run off a USB thumb drive. If you're in that boat, there are some old but still accurate instructions on the Vyatta forums (a great resource if you get stuck).
Once you have your boot media -- either a CD-ROM or a flash drive -- ready to go, you can boot up your machine and get started. It's important to realize that what you're actually booting isn't strictly an installer -- it's a fully functional Vyatta environment. To burn that environment onto permanent storage, such as a hard drive or a CompactFlash card, so that you can save your configuration easily, you'll need to log in (both the username and password are "vyatta") and run the install-system command.
That will run you through a few basic options about whether to enable software RAID (if you have more than one hard drive you want to mirror) and what disk configuration to use. If you're not sure, you can generally accept the defaults on just about everything. Once the installer has done its job, you can shut down the machine, remove the media, and turn it back on. If all went well, you should be presented with another login prompt.
Covering the basics
To get into configuration mode, you'll need to enter the configure command. When you're done inputting a series of commands, you'll tell Vyatta you want to actually make them active by running commit. If you want to make them permanent, you can type save. Once you're done with configure mode, you can type exit to drop you back out to where you can run commands like show configuration cmds, which will dump out the entire saved configuration so you can review it.
The first thing I did was get the Vyatta router configured so that I could access it over the network. As I am lazy, typing into a CLI from a real console with no copy and paste is a real drag for me. To that end, there are a few things you'll probably want to do right off the bat.
IPv4 on the inside
First, you'll want to give your router an IPv4 address on its inside interface. In my case, I had two Ethernet interfaces: One that I wanted to use for my outside (eth0) connection, and one that I wanted to use on the inside (eth1). Setting up the outside comes later once we have some firewall rules in place to protect it:
set interfaces ethernet eth1 address '192.168.1.1/24'