The general format of a configuration file is quite simple. Each line contains a keyword and one or more arguments. For simplicity, most lines only contain one argument. The following sections describe each keyword, generally in the order they are listed in GENERIC, although some related keywords have been grouped together in a single section (such as Networking) even though they are actually scattered throughout the GENERIC file. For an exhaustive list of architecture dependent options and devices, see the NOTES file in the same directory as GENERIC. For architecture independent options, see /usr/src/sys/conf/NOTES. Note: NOTES does not exist in FreeBSD 4.X. Instead, see the LINT file for detailed explanations of options and devices in GENERIC. LINT served two purposes in 4.X: to provide a reference for choosing kernel options when building a custom kernel, and to provide a kernel configuration with as many tweakable options tweaked to non-default values as possible. The reason behind this was that such a configuration helped (and still does) a lot when testing new code and changes to existing code that may cause conflicts with other parts of the kernel.

However, the kernel configuration framework went through some heavy changes in 5.X; one example of this is that the driver configuration options were moved to a hints file so that they could be changed and loaded dynamically at boot time, and LINT could not contain those hints anymore. For this and other reasons, the LINT file was renamed to NOTES and retained mostly the first reason for its existence: documenting the available options for user convenience. The following is an example of the GENERIC kernel configuration file with various additional comments where needed for clarity. This example should match your copy in /usr/src/sys/i386/conf/GENERIC fairly closely. This is the machine architecture. It must be either alpha, amd64, i386, ia64, pc98, powerpc, or sparc64. The above option specifies the type of CPU you have in your system. CPU), but for a custom kernel it is best to specify only the CPU you have. If you are unsure of your CPU type, you can check the /var/run/dmesg.boot file to view your boot messages.

CPU is still provided in the source of FreeBSD, but it is disabled by default in both -STABLE and -CURRENT. Build the userland and kernel on a newer machine and install on the 386 using the precompiled /usr/obj files (see Section 19.5 for details). CPU support in the kernels of the installation CD-ROM. The first of these options is probably the easiest of all, but you will need a lot of disk space which, on a 386-class machine, may be difficult to find. This is the identification of the kernel. You should change this to whatever you named your kernel, i.e. MYKERNEL if you have followed the instructions of the previous examples. The value you put in the ident string will print when you boot up the kernel, so it is useful to give the new kernel a different name if you want to keep it separate from your usual kernel (e.g., you want to build an experimental kernel).

The maxusers option sets the size of a number of important system tables. This number is supposed to be roughly equal to the number of simultaneous users you expect to have on your machine. In FreeBSD 5.X and above, maxusers will default to 0 if not specified. If you are using an version of FreeBSD earlier than 4.5, or you want to manage it yourself you will want to set maxusers to at least 4, especially if you are using the X Window System or compiling software. 1, then you can only have 36 simultaneous processes, including the 18 or so that the system starts up at boot time and the 15 or so you will probably create when you start the X Window System. Even a simple task like reading a manual page will start up nine processes to filter, decompress, and view it. Setting maxusers to 64 will allow you to have up to 1044 simultaneous processes, which should be enough for nearly all uses.