DEVELOPMENT(7)

NAME
development - introduction to development with the FreeBSD codebase

DESCRIPTION
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. You need a good 12-17GB of disk space on one machine to make this work conveniently.

SETTING UP THE ENVIRONMENT ON THE MASTER SERVER
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 huge partition called /FreeBSD. 8-12GB is recommended. This partition will contain nearly all the development environment, including the CVS 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 5GB.

On the master server, use csup(1) to automatically pull down and maintain the FreeBSD CVS archive once a day. The first pull will take a long time, it is several gigabytes, but once you have it, the daily synchronizations will be quite small.

    mkdir /FreeBSD/FreeBSD-CVS
    rm -rf /home/ncvs
    ln -s /FreeBSD/FreeBSD-CVS /home/ncvs

The cron(8) job should look something like this (please randomize the time of day!). Note that you can use the csup(1) configuration file example directly from /usr/share/examples without modification by supplying appropriate arguments to csup(1).

    33 6 * * *      /usr/bin/csup -r 20 -L 2 -h cvsup.freebsd.org /usr/share/examples/cvsup/cvs-supfile

Run the csup(1) manually the first time to pull down the archive. It could take all day depending on how fast your connection is! You will run all csup(1) and cvs(1) operations as “root” and you need to set up a ~/.cvsrc (/root/.cvsrc) file, as shown below, for proper cvs(1) operation. Using ~/.cvsrc to specify cvs(1) defaults is an excellent way to “file and forget”, but you should never forget that you put them in there.

    # cvs -q
    diff -u
    update -Pd
    checkout -P

Now use cvs(1) to check out a -STABLE source tree and a -CURRENT source tree, as well as ports and docs, to create your initial source environment. 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/FreeBSD-4.x
    mkdir /FreeBSD/FreeBSD-current
    cd /FreeBSD/FreeBSD-4.x
    cvs -d /home/ncvs checkout -rRELENG_4 src
    cd /FreeBSD/FreeBSD-current
    cvs -d /home/ncvs checkout src
    cvs -d /home/ncvs checkout ports
    cvs -d /home/ncvs checkout doc

Now create a softlink for /usr/src and /usr/src2. On the main server I always point /usr/src at -STABLE and /usr/src2 at -CURRENT. On client machines I usually do not have a /usr/src2 and I make /usr/src point at whatever version of FreeBSD the client box is intended to run.

    cd /usr
    rm -rf src src2
    ln -s /FreeBSD/FreeBSD-4.x/src src	(could be -CURRENT on a client)
    ln -s /FreeBSD/FreeBSD-current/src src2	(MASTER SERVER ONLY)

Now you have to make a choice for /usr/obj. Well, hopefully you made it already and chose the partition method. If you chose poorly you probably intend to put it in /FreeBSD and, if so, this is what you want to do:

    (ONLY IF YOU MADE A POOR CHOICE AND PUT /usr/obj in /FreeBSD!)
    mkdir /FreeBSD/obj
    cd /usr
    rm -rf obj
    ln -s /FreeBSD/obj obj

Alternatively you may chose simply to leave /usr/obj in /usr. If your /usr is large enough this will work, but I do not recommend it for safety reasons (/usr/obj is constantly being modified, /usr is not).

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 CVS. It is sitting right there in the master CVS archive and I have even told you to check it out (see above). 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 CVS branch, so its always -CURRENT even on a -STABLE box. This is what you do:

    (THESE COMMANDS ON THE MASTER SERVER AND ON ALL CLIENTS)
    cd /usr
    rm -rf ports
    ln -s /FreeBSD/FreeBSD-current/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:

    WRKDIRPREFIX=/usr/ports.workdir

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.

EXPORTING VIA NFS FROM THE MASTER SERVER
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_enable="YES"
    nfs_server_flags="-u -t -n 4"

THE CLIENT ENVIRONMENT
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:

    nfs_client_enable="YES"

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/FreeBSD-current/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.

    (ON EACH CLIENT)
    cd /usr
    rm -rf ports src
    ln -s /FreeBSD/FreeBSD-current/ports ports
    ln -s /FreeBSD/FreeBSD-XXX/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

BUILDING KERNELS
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 KERNELS
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

BUILDING THE WORLD
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

INSTALLING THE WORLD
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.

    (ON THE CLIENT)
    (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.

DOING DEVELOPMENT ON A CLIENT (NOT JUST INSTALLING)
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!

MAINTAINING A LOCAL BRANCH
I have described how to maintain two versions of the source tree, a stable version in /FreeBSD/FreeBSD-4.x and a current version in /FreeBSD/FreeBSD-current. 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 CVS or another source code management system (SubVersion, Perforce, BitKeeper) with its own repository. Since the main FreeBSD tree is based on CVS, the former is convenient.

First, you need to modify your csup(1) environment to avoid it modifying the local changes you have committed to the repository. It is important to remove the delete keyword from your supfile and to add the CVSROOT subdirectory to your refuse file. For more information, see csup(1).

The FreeBSD version of cvs(1) examines a custom environmental variable, CVS_LOCAL_BRANCH_NUM, which specifies an integer to use when doing a cvs(1) tag/rtag. Set this number to something high (say 1000) to avoid colliding with potential future branches of the main repository. For example, branching a file with version 1.4 produces 1.4.1000. Future commits to this branch will produce revisions 1.4.1000.1, 1.4.1000.2, etc.

To fork your local branch, do:

    cvs rtag -r RELENG_4 -b LOCAL_RELENG_4 src

After this, you can check out a copy from your local repository using the new tag and begin making changes and committing them. For more information on using CVS, see cvs(1).

WARNING! The csup(1) utility may blow away changes made on a local branch in some situations. This has been reported to occur when the master CVS repository is directly manipulated or an RCS file is changed. At this point, csup(1) notices that the client and server have entirely different RCS files, so it does a full replace instead of trying to send just deltas. Ideally this situation should never arise, but in the real world it happens all the time.

While this is the only scenario where the problem should crop up, there have been some suspicious-sounding reports of CVS_LOCAL_BRANCH_NUM lossage that cannot be explained by this alone. Bottom line is, if you value your local branch then you should back it up before every update.

UPDATING VIA CVS
The advantage of using csup(1) to maintain an updated copy of the CVS repository instead of using it to maintain source trees directly is that you can then pick and choose when you bring your source tree (or pieces of your source tree) up to date. By using a cron(8) job to maintain an updated CVS repository, you can update your source tree at any time without any network cost as follows:

    (on the main development server)
    cd /usr/src
    cvs -d /home/ncvs update
    cd /usr/src2
    cvs -d /home/ncvs update
    cd /usr/ports
    cvs -d /home/ncvs update

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 cvs(1) operations you do will be done as “root”, and that certain options are required for CVS to operate properly on the FreeBSD repository. For example, -Pd is necessary when running cvs update. These options are typically placed in your ~/.cvsrc (as already described) so you do not have to re-specify them every time you run a cvs(1) command. Maintaining the CVS repository also gives you far more flexibility in regards to breaking out multiple versions of the source tree. It is a good idea to give your /FreeBSD partition a lot of space (I recommend 8-12GB) precisely for that reason. If you can make it 15GB I would do it.

I generally do not cvs update via a cron(8) job. This is because I generally want the source to not change out from under me when I am developing code. Instead I manually update the source every so often... when I feel it is a good time. My recommendation is to only keep the CVS repository synchronized via cron(8).

SEE ALSO
crontab(1), crontab(5), make.conf(5), build(7), firewall(7), release(7), tuning(7), diskless(8)

HISTORY
The development manual page was originally written by Matthew Dillon <dillon@FreeBSD.org> and first appeared in FreeBSD 5.0, December 2002.