The system file is used for customizing the operation of the operating system kernel. The recommended procedure is to preserve the original system file before modifying it.

The system file contains commands which are read by the kernel during initialization and used to customize the operation of your system. These commands are useful for modifying the system's treatment of its loadable kernel modules.

The syntax of the system file consists of a list of keyword/value pairs which are recognized by the system as valid commands. Comment lines must begin with an asterisk (*) or a hash mark (#) and end with a newline character. All commands are case-insensitive except where noted. A command line can be no more than 80 characters in length.

Commands that modify the system's operation with respect to loadable kernel modules require you to specify the module type by listing the module's namespace. The following namespaces are currently supported on all platforms:

drv

Modules in this namespace are device drivers.

exec

Modules in this namespace are execution format modules. The following exec modules are currently provided:

Only on SPARC system:

aoutexec

Only on IA system:

coffexec

On SPARC and IA systems:

elfexec intpexec javaexec

fs

These modules are filesystems.

sched

These modules implement a process scheduling algorithm.

strmod

These modules are STREAMS modules.

sys

These modules implement loadable system-call modules.

misc

These modules do not fit into any of the above categories, so are considered "miscellaneous" modules.

SPARC only:

dacf

These modules provide rules and actions for device auto-configuration.

tod

These modules provide support for the time of day hardware.

cpu

These modules provide CPU-specific kernel routines.

A description of each of the supported commands follows:

exclude: <namespace>/<modulename>

Do not allow the listed loadable kernel module to be loaded. exclude commands are cumulative; the list of modules to exclude is created by combining every exclude entry in the system file.

include: <namespace>/<modulename>

Include the listed loadable kernel module. This is the system's default, so using include does not modify the system's operation. include commands are cumulative.

forceload: <namespace>/<modulename>

Force this kernel module to be loaded during kernel initialization. The default action is to automatically load the kernel module when its services are first accessed. forceload commands are cumulative.

rootdev: <device name>

Set the root device to the listed value instead of using the default root device as supplied by the boot program.

rootfs: <root filesystem type>

Set the root filesystem type to the listed value.

moddir: <first module path>[[{:, }<second ...>]...]

Set the search path for loadable kernel modules. This command operates very much like the PATH shell variable. Multiple directories to search can be listed together, delimited either by blank spaces or colons.

set [<module>:]<symbol> {=, |, &} [~][-]<value>

Set an integer or character pointer in the kernel or in the selected kernel module to a new value. This command is used to change kernel and module parameters and thus modify the operation of your system. Assignment operations are not cumulative, whereas bitwise AND and OR operations are cumulative.

Operations that are supported for modifying integer variables are: simple assignment, inclusive bitwise OR, bitwise AND, one's complement, and negation. Variables in a specific loadable module can be targeted for modification by specifying the variable name prefixed with the kernel module name and a colon (:) separator. Values can be specified as hexadecimal (0x10), Octal (046), or Decimal (5).

The only operation supported for modifying character pointers is simple assignment. Static string data such as character arrays cannot be modified using the set command. Use care and ensure that the variable you are modifying is in fact a character pointer. The set command is very powerful, and will likely cause problems if used carelessly. The entire command, including the quoted string, cannot exceed 80 characters. The following escape sequences are supported within the quoted string:

\n (newline) \t (tab) \b (backspace)

boot(1M), init(1M), kernel(1M)

Lines in the system file must be fewer than 80 characters in length.

Use care when modifying the system file; it modifies the operation of the kernel. If you preserved the original system file, you can boot using boot -a, which will ask you to specify the path to the saved file. This should allow the system to boot correctly. If you cannot locate a system file that will work, you may specify /dev/null. This acts as an empty system file, and the system will attempt to boot using its default settings.

The /etc/system file is read only once, at boot time.