In FreeBSD 9.2 and 10.0, DTrace support is built into the GENERIC kernel. Users of earlier versions of FreeBSD or who prefer to statically compile in DTrace support should add the following lines to a custom kernel configuration file and recompile the kernel using the instructions in Chapter 9, Configuring the FreeBSD Kernel:

options         KDTRACE_HOOKS
options         DDB_CTF
options		DEBUG=-g

Users of the AMD64 architecture should also add this line:

options         KDTRACE_FRAME

This option provides support for FBT. While DTrace will work without this option, there will be limited support for function boundary tracing.

Once the FreeBSD system has rebooted into the new kernel, or the DTrace kernel modules have been loaded using kldload dtraceall, the system will need support for the Korn shell as the DTrace Toolkit has several utilities written in ksh. Make sure that the shells/ksh93 package or port is installed. It is also possible to run these tools under shells/pdksh or shells/mksh.

Finally, install the current DTrace Toolkit, a collection of ready-made scripts for collecting system information. There are scripts to check open files, memory, CPU usage, and a lot more. FreeBSD 10 installs a few of these scripts into /usr/share/dtrace. On other FreeBSD versions, or to install the full DTrace Toolkit, use the sysutils/DTraceToolkit package or port.

The DTrace Toolkit includes many scripts in the special language of DTrace. This language is called the D language and it is very similar to C++. An in depth discussion of the language is beyond the scope of this document. It is extensively discussed at http://wikis.oracle.com/display/DTrace/Documentation.