DEVELOPMENT(7) FreeBSD Miscellaneous Information Manual DEVELOPMENT(7)


developmentintroduction to development with the FreeBSD codebase


This manual page describes how an ordinary system operator, UNIX administrator, or developer can, without any special permission, obtain, maintain, and modify the FreeBSD codebase as well as how to maintain a master build which can then be exported to other machines in your network. This manual page is targeted to system operators, programmers, and developers.

Please note that what is being described here is based on a complete FreeBSD environment, not just the FreeBSD kernel. The methods described here are as applicable to production installations as it is to development environments.


Your master server should always run a stable, production version of the FreeBSD operating system. This does not prevent you from doing -CURRENT builds or development. The last thing you want to do is to run an unstable environment on your master server which could lead to a situation where you lose the environment and/or cannot recover from a mistake.

Create a partition called /FreeBSD. Approximately 20GB is recommended. This partition will contain nearly all the development environment, including the subversion tree, broken-out source, and possibly even object files. You are going to export this partition to your other machines via a READ-ONLY NFS export so do not mix it with other more security-sensitive partitions.

You have to make a choice in regards to /usr/obj. You can put /usr/obj in /FreeBSD or you can make /usr/obj its own partition. I recommend making it a separate partition for several reasons. First, as a safety measure since this partition is written to a great deal. Second, because you typically do not have to back it up. Third, because it makes it far easier to mix and match the development environments which are described later in this document. I recommend a /usr/obj partition of at least 12GB.

On the master server, use svn(1) to pull down and maintain the FreeBSD source. The first pull will take a long time, it is several gigabytes, but once you have it, the updates will be quite small. Run all svn(1) operations as “ root

Keeping the broken-out source and ports in /FreeBSD allows you to export it to other machines via read-only NFS. This also means you only need to edit/maintain files in one place and all your clients automatically pick up the changes.

mkdir /FreeBSD 
cd /FreeBSD 
svn co https://svn.freebsd.org/ports/head ports 
svn co https://svn.freebsd.org/doc/head doc 
svn co https://svn.freebsd.org/base/head src 
cd /usr 
rm -rf src 
ln -s /FreeBSD/src src

Note that exporting /usr/obj via read-only NFS to your other boxes will allow you to build on your main server and install from your other boxes. If you also want to do builds on some or all of the clients you can simply have /usr/obj be a local directory on those clients. You should never export /usr/obj read-write, it will lead to all sorts of problems and issues down the line and presents a security problem as well. It is far easier to do builds on the master server and then only do installs on the clients.

I usually maintain my ports tree via svn or portsnap. With some fancy softlinks you can make the ports tree available both on your master server and on all of your other machines. Note that the ports tree exists only on the HEAD ports branch, so its always usable even on a -STABLE box. This is what you do:

cd /usr 
rm -rf ports 
ln -s /FreeBSD/ports ports 
cd /usr/ports      (this pushes into the softlink) 
rm -rf distfiles   (ON MASTER SERVER ONLY) 
ln -s /usr/ports.distfiles distfiles (ON MASTER SERVER ONLY) 
mkdir /usr/ports.distfiles 
mkdir /usr/ports.workdir

Since /usr/ports is softlinked into what will be read-only on all of your clients, you have to tell the ports system to use a different working directory to hold ports builds. You want to add a line to your make.conf(5) file on the master server and on all your clients:


You should try to make the directory you use for the ports working directory as well as the directory used to hold distfiles consistent across all of your machines. If there is not enough room in /usr/ports.distfiles and /usr/ports.workdir I usually make those softlinks (since this is on /usr these are per-machine) to where the distfiles and working space really are.


The master server needs to export /FreeBSD and /usr/obj via NFS so all the rest of your machines can get at them. I strongly recommend using a read-only export for both security and safety. The environment I am describing in this manual page is designed primarily around read-only NFS exports. Your exports file on the master server should contain the following lines:

/FreeBSD -ro -alldirs -maproot=root: -network YOURLAN -mask YOURLANMASK 
/usr/obj -ro -alldirs -maproot=root: -network YOURLAN -mask YOURLANMASK

Of course, NFS server operations must also be configured on that machine. This is typically done via your /etc/rc.conf:

nfs_server_flags="-u -t -n 4"


All of your client machines can import the development/build environment directory simply by NFS mounting /FreeBSD and /usr/obj from the master server. A typical /etc/fstab entry on your client machines will be something like this:

masterserver:/FreeBSD     /FreeBSD        nfs     ro,bg    0       0 
masterserver:/usr/obj     /usr/obj        nfs     ro,bg    0       0

And, of course, you should configure the client for NFS client operations via /etc/rc.conf. In particular, this will turn on nfsiod(8) which will improve client-side NFS performance:


Each client should create softlinks for /usr/ports and /usr/src that point into the NFS-mounted environment. If a particular client is running -CURRENT, /usr/src should be a softlink to /FreeBSD/src. If it is running -STABLE, /usr/src should be a softlink to /FreeBSD/FreeBSD-4.x/src. I do not usually create a /usr/src2 softlink on clients, that is used as a convenient shortcut when working on the source code on the master server only and could create massive confusion (of the human variety) on a client.

cd /usr 
rm -rf ports src 
ln -s /FreeBSD/ports ports 
ln -s /FreeBSD/src src

Do not forget to create the working directories so you can build ports, as previously described. If these are not good locations, make them softlinks to the correct location. Remember that /usr/ports/distfiles is exported by the master server and is therefore going to point to the same place (typically /usr/ports.distfiles) on every machine.

mkdir /usr/ports.distfiles 
mkdir /usr/ports.workdir


Here is how you build a -STABLE kernel (on your main development box). If you want to create a custom kernel, copy GENERIC to KERNELNAME and then edit it before configuring and building. The kernel configuration file lives in /usr/src/sys/i386/conf/KERNELNAME.

cd /usr/src 
make buildkernel KERNCONF=KERNELNAME

WARNING! If you are familiar with the old config/cd/make method of building a -STABLE kernel, note that the config(8) method will put the build environment in /usr/src/sys/i386/compile/KERNELNAME instead of in /usr/obj.

Building a -CURRENT kernel

cd /usr/src2  (on the master server) 
make buildkernel KERNCONF=KERNELNAME


Installing a -STABLE kernel (typically done on a client, only do this on your main development server if you want to install a new kernel for your main development server):

cd /usr/src 
make installkernel KERNCONF=KERNELNAME

If you are using the older config/cd/make build mechanism for -STABLE, you would install using:

cd /usr/src/sys/i386/compile/KERNELNAME 
make install

Installing a -CURRENT kernel (typically done only on a client)

(remember /usr/src is pointing to the client's specific environment) 
cd /usr/src 
make installkernel KERNCONF=KERNELNAME


This environment is designed such that you do all builds on the master server, and then install from each client. You can do builds on a client only if /usr/obj is local to that client. Building the world is easy:

cd /usr/src 
make buildworld

If you are on the master server you are running in a -STABLE environment, but that does not prevent you from building the -CURRENT world. Just cd(1) into the appropriate source directory and you are set. Do not accidentally install it on your master server though!

cd /usr/src2 
make buildworld


You can build on your main development server and install on clients. The main development server must export /FreeBSD and /usr/obj via read-only NFS to the clients.

NOTE!!! If /usr/obj is a softlink on the master server, it must also be the EXACT SAME softlink on each client. If /usr/obj is a directory in /usr or a mount point on the master server, then it must be (interchangeably) a directory in /usr or a mount point on each client. This is because the absolute paths are expected to be the same when building the world as when installing it, and you generally build it on your main development box and install it from a client. If you do not set up /usr/obj properly you will not be able to build on machine and install on another.

(remember /usr/src is pointing to the client's specific environment) 
cd /usr/src 
make installworld

WARNING! If builds work on the master server but installs do not work from the clients, for example you try to install and the client complains that the install tried to write into the read-only /usr/obj, then it is likely that the make.conf(5) file on the client does not match the one on the master server closely enough and the install is trying to install something that was not built.


Developers often want to run buildkernel's or buildworld's on client boxes simply to life-test the box. You do this in the same manner that you buildkernel and buildworld on your master server. All you have to do is make sure that /usr/obj is pointing to local storage. If you followed my advise and made /usr/obj its own partition on the master server, then it is typically going to be an NFS mount on the client. Simply unmounting /usr/obj will leave you with a /usr/obj that is a subdirectory in /usr which is typically local to the client. You can then do builds to your heart's content!


There is absolutely nothing preventing you from breaking out other versions of the source tree into /FreeBSD/XXX. In fact, my /FreeBSD partition also contains OpenBSD, NetBSD, and various flavors of Linux. You may not necessarily be able to build non- FreeBSD operating systems on your master server, but being able to collect and manage source distributions from a central server is a very useful thing to be able to do and you can certainly export to machines which can build those other operating systems.

Many developers choose to maintain a local branch of FreeBSD to test patches or build a custom distribution. This can be done with svn or another source code management system (git, mercurial, Perforce, BitKeeper) with its own repository.


By using a cron(8) job to maintain an updated svn repository, the source tree can be updated at any time as follows:

(on the main development server) 
cd /usr 
svn update src doc ports

It is that simple, and since you are exporting the whole lot to your clients, your clients have immediate visibility into the updated source. This is a good time to also remind you that most of the svn(1) operations you do will be done as “ root”.



The development manual page was originally written by Matthew Dillon <dillon@FreeBSD.org> and first appeared in FreeBSD 5.0, December 2002. It was since extensively modified by Eitan Adler <eadler@FreeBSD.org> to reflect the repository conversion from cvs to svn.
March 7, 2013 FreeBSD