development -- introduction to development with the FreeBSD codebase
This manual page describes how an ordinary sysop, UNIX admin, or
developer can, without any special permission, obtain, maintain, and modify
the FreeBSD codebase as well as how to maintaining 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 [Toc] [Back] 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 cvsup 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 syncs will
be quite small.
mkdir /FreeBSD/FreeBSD-CVS
rm -rf /home/ncvs
ln -s /FreeBSD/FreeBSD-CVS /home/ncvs
The cron job should look something like this (please randomize the time
of day!). Note that you can use the cvsup file example directly from
/usr/share/examples without modification by supplying appropriate arguments
to cvsup.
33 6 * * * /usr/local/bin/cvsup -g -r 20 -L 2 -h cvsup.freebsd.org /usr/share/examples/cvsup/cvs-supfile
Run the cvsup 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
cvsup and cvs operations as root and you need to set up a ~/.cvsrc
(/root/.cvsrc) file, as shown below, for proper cvs operation. Using
~/.cvsrc to specify cvs 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 to checkout 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've 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
/etc/make.conf 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 isn't 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 [Toc] [Back] 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 [Toc] [Back] 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 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
Don't 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, cp GENERIC to YOURKERNEL 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 method will put the build
environment in /usr/src/sys/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/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
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 readonly
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 setup
/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 /etc/make.conf 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) [Toc] [Back] 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 [Toc] [Back] 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 cvsup 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 cvsup(1).
The FreeBSD version of CVS examines a custom environmental variable,
CVS_LOCAL_BRANCH_NUM, which specifies an integer to use when doing a cvs
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 cvsup 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, cvsup 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 can't be explained by this alone. Bottom line is, if you value
your local branch then you should back it up before every update.
The advantage of using cvsup 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 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 immediately visibility into the updated
source. This is a good time to also remind you that most of the cvs
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 respecify them every time you run a CVS 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 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.
crontab(1), crontab(5), build(7), firewall(7), release(7), tuning(7),
diskless(8)
The development manual page was originally written by Matthew Dillon
<[email protected]> and first appeared in FreeBSD 5.0, December 2002.
FreeBSD 5.2.1 December 21, 2002 FreeBSD 5.2.1 [ Back ] |
