Typically, you will be adding a buildslave to an existing buildmaster, to provide additional architecture coverage. The buildbot administrator will give you several pieces of information necessary to connect to the buildmaster. You should also be somewhat familiar with the project being tested, so you can troubleshoot build problems locally.
The buildbot exists to make sure that the project's stated “how to build it” process actually works. To this end, the buildslave should run in an environment just like that of your regular developers. Typically the project build process is documented somewhere (README, INSTALL, etc), in a document that should mention all library dependencies and contain a basic set of build instructions. This document will be useful as you configure the host and account in which the buildslave runs.
Here's a good checklist for setting up a buildslave:
It is recommended (although not mandatory) to set up a separate user
account for the buildslave. This account is frequently named
buildbot or buildslave. This serves to isolate your
personal working environment from that of the slave's, and helps to
minimize the security threat posed by letting possibly-unknown
contributors run arbitrary code on your system. The account should
have a minimum of fancy init scripts.
Follow the instructions given earlier (see Installing the code).
If you use a separate buildslave account, and you didn't install the
buildbot code to a shared location, then you will need to install it
with --home=~ for each account that needs it.
Make sure the host can actually reach the buildmaster. Usually the buildmaster is running a status webserver on the same machine, so simply point your web browser at it and see if you can get there. Install whatever additional packages or libraries the project's INSTALL document advises. (or not: if your buildslave is supposed to make sure that building without optional libraries still works, then don't install those libraries).
Again, these libraries don't necessarily have to be installed to a site-wide shared location, but they must be available to your build process. Accomplishing this is usually very specific to the build process, so installing them to /usr or /usr/local is usually the best approach.
Follow the instructions in the INSTALL document, in the buildslave's account. Perform a full CVS (or whatever) checkout, configure, make, run tests, etc. Confirm that the build works without manual fussing. If it doesn't work when you do it by hand, it will be unlikely to work when the buildbot attempts to do it in an automated fashion.
This should be somewhere in the buildslave's account, typically named after the project which is being tested. The buildslave will not touch any file outside of this directory. Something like ~/Buildbot or ~/Buildslaves/fooproject is appropriate.
When the buildbot admin configures the buildmaster to accept and use your buildslave, they will provide you with the following pieces of information:
Now run the 'buildbot' command as follows:
buildbot create-slave BASEDIR MASTERHOST:PORT SLAVENAME PASSWORD
This will create the base directory and a collection of files inside,
including the buildbot.tac file that contains all the
information you passed to the buildbot command.
When it first connects, the buildslave will send a few files up to the buildmaster which describe the host that it is running on. These files are presented on the web status display so that developers have more information to reproduce any test failures that are witnessed by the buildbot. There are sample files in the info subdirectory of the buildbot's base directory. You should edit these to correctly describe you and your host.
BASEDIR/info/admin should contain your name and email address. This is the “buildslave admin address”, and will be visible from the build status page (so you may wish to munge it a bit if address-harvesting spambots are a concern).
BASEDIR/info/host should be filled with a brief description of the host: OS, version, memory size, CPU speed, versions of relevant libraries installed, and finally the version of the buildbot code which is running the buildslave.
The optional BASEDIR/info/access_uri can specify a URI which will
connect a user to the machine. Many systems accept ssh://hostname URIs
for this purpose.
If you run many buildslaves, you may want to create a single ~buildslave/info file and share it among all the buildslaves with symlinks.