21.4. Rebuilding “world”

21.4.7.1. Saving the Output

It is a good idea to save the output you get from running make(1) to another file. If something goes wrong you will have a copy of the error message. While this might not help you in diagnosing what has gone wrong, it can help others if you post your problem to one of the FreeBSD mailing lists.

The easiest way to do this is to use the script(1) command, with a parameter that specifies the name of the file to save all output to. You would do this immediately before rebuilding the world, and then type exit when the process has finished.

# script /var/tmp/mw.out
Script started, output file is /var/tmp/mw.out   
# make TARGET
... compile, compile, compile ...     
# exit
Script done, ...

If you do this, do not save the output in /tmp. This directory may be cleared next time you reboot. A better place to store it is in /var/tmp (as in the previous example) or in root's home directory.

21.4.7.2. Compile the Base System

You must be in the /usr/src directory:

# cd /usr/src

(unless, of course, your source code is elsewhere, in which case change to that directory instead).

To rebuild the world you use the make(1) command. This command reads instructions from the Makefile, which describes how the programs that comprise FreeBSD should be rebuilt, the order in which they should be built, and so on.

The general format of the command line you will type is as follows:

# make -x -DVARIABLE target

In this example, -x is an option that you would pass to make(1). See the make(1) manual page for an example of the options you can pass.

-DVARIABLE passes a variable to the Makefile. The behavior of the Makefile is controlled by these variables. These are the same variables as are set in /etc/make.conf, and this provides another way of setting them.

# make -DNO_PROFILE target

is another way of specifying that profiled libraries should not be built, and corresponds with the

NO_PROFILE=    true    #    Avoid compiling profiled libraries

line in /etc/make.conf.

target tells make(1) what you want to do. Each Makefile defines a number of different “targets”, and your choice of target determines what happens.

Some targets are listed in the Makefile, but are not meant for you to run. Instead, they are used by the build process to break out the steps necessary to rebuild the system into a number of sub-steps.

Most of the time you will not need to pass any parameters to make(1), and so your command like will look like this:

# make target

Where target will be one of many build options. The first target should always be buildworld.

As the names imply, buildworld builds a complete new tree under /usr/obj, and installworld, another target, installs this tree on the current machine.

Having separate options is very useful for two reasons. First, it allows you to do the build safe in the knowledge that no components of your running system will be affected. The build is “self hosted”. Because of this, you can safely run buildworld on a machine running in multi-user mode with no fear of ill-effects. It is still recommended that you run the installworld part in single user mode, though.

Secondly, it allows you to use NFS mounts to upgrade multiple machines on your network. If you have three machines, A, B and C that you want to upgrade, run make buildworld and make installworld on A. B and C should then NFS mount /usr/src and /usr/obj from A, and you can then run make installworld to install the results of the build on B and C.

Although the world target still exists, you are strongly encouraged not to use it.

Run

# make buildworld

It is possible to specify a -j option to make which will cause it to spawn several simultaneous processes. This is most useful on multi-CPU machines. However, since much of the compiling process is IO bound rather than CPU bound it is also useful on single CPU machines.

On a typical single-CPU machine you would run:

# make -j4 buildworld

make(1) will then have up to 4 processes running at any one time. Empirical evidence posted to the mailing lists shows this generally gives the best performance benefit.

If you have a multi-CPU machine and you are using an SMP configured kernel try values between 6 and 10 and see how they speed things up.

21.4.7.3. Timings

Many factors influence the build time, but fairly recent machines may only take a one or two hours to build the FreeBSD-STABLE tree, with no tricks or shortcuts used during the process. A FreeBSD-CURRENT tree will take somewhat longer.

21.4.11.1. mergemaster

Contributed by Tom Rhodes.

The mergemaster(8) utility is a Bourne script that will aid you in determining the differences between your configuration files in /etc, and the configuration files in the source tree /usr/src/etc. This is the recommended solution for keeping the system configuration files up to date with those located in the source tree.

To begin simply type mergemaster at your prompt, and watch it start going. mergemaster will then build a temporary root environment, from / down, and populate it with various system configuration files. Those files are then compared to the ones currently installed in your system. At this point, files that differ will be shown in diff(1) format, with the + sign representing added or modified lines, and - representing lines that will be either removed completely, or replaced with a new line. See the diff(1) manual page for more information about the diff(1) syntax and how file differences are shown.

mergemaster(8) will then show you each file that displays variances, and at this point you will have the option of either deleting the new file (referred to as the temporary file), installing the temporary file in its unmodified state, merging the temporary file with the currently installed file, or viewing the diff(1) results again.

Choosing to delete the temporary file will tell mergemaster(8) that we wish to keep our current file unchanged, and to delete the new version. This option is not recommended, unless you see no reason to change the current file. You can get help at any time by typing ? at the mergemaster(8) prompt. If the user chooses to skip a file, it will be presented again after all other files have been dealt with.

Choosing to install the unmodified temporary file will replace the current file with the new one. For most unmodified files, this is the best option.

Choosing to merge the file will present you with a text editor, and the contents of both files. You can now merge them by reviewing both files side by side on the screen, and choosing parts from both to create a finished product. When the files are compared side by side, the l key will select the left contents and the r key will select contents from your right. The final output will be a file consisting of both parts, which can then be installed. This option is customarily used for files where settings have been modified by the user.

Choosing to view the diff(1) results again will show you the file differences just like mergemaster(8) did before prompting you for an option.

After mergemaster(8) is done with the system files you will be prompted for other options. mergemaster(8) may ask if you want to rebuild the password file and will finish up with an option to remove left-over temporary files.

21.4.11.2. Manual Update

If you wish to do the update manually, however, you cannot just copy over the files from /usr/src/etc to /etc and have it work. Some of these files must be “installed” first. This is because the /usr/src/etc directory is not a copy of what your /etc directory should look like. In addition, there are files that should be in /etc that are not in /usr/src/etc.

If you are using mergemaster(8) (as recommended), you can skip forward to the next section.

The simplest way to do this by hand is to install the files into a new directory, and then work through them looking for differences.

You need to build a dummy set of directories to install the new /etc and other files into. /var/tmp/root is a reasonable choice, and there are a number of subdirectories required under this as well.

# mkdir /var/tmp/root
# cd /usr/src/etc
# make DESTDIR=/var/tmp/root distrib-dirs distribution

This will build the necessary directory structure and install the files. A lot of the subdirectories that have been created under /var/tmp/root are empty and should be deleted. The simplest way to do this is to:

# cd /var/tmp/root
# find -d . -type d | xargs rmdir 2>/dev/null

This will remove all empty directories. (Standard error is redirected to /dev/null to prevent the warnings about the directories that are not empty.)

/var/tmp/root now contains all the files that should be placed in appropriate locations below /. You now have to go through each of these files, determining how they differ with your existing files.

Note that some of the files that will have been installed in /var/tmp/root have a leading “.”. At the time of writing the only files like this are shell startup files in /var/tmp/root/ and /var/tmp/root/root/, although there may be others (depending on when you are reading this). Make sure you use ls -a to catch them.

The simplest way to do this is to use diff(1) to compare the two files:

# diff /etc/shells /var/tmp/root/etc/shells

This will show you the differences between your /etc/shells file and the new /var/tmp/root/etc/shells file. Use these to decide whether to merge in changes that you have made or whether to copy over your old file.