---
name: "SYSINIT"
section: "9"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/SYSINIT"
---

# SYSINIT(9)

a framework for dynamic kernel initialization

## NAME

**SYSINIT**, **SYSUNINIT** – a framework for dynamic kernel initialization

## SYNOPSIS

**#include \<sys/param.h\>**

**#include \<sys/kernel.h\>**

**SYSINIT**(*uniquifier*, *enum sysinit\_sub\_id subsystem*, *enum sysinit\_elem\_order order*, *sysinit\_cfunc\_t func*, *const void \*ident*);

**SYSUNINIT**(*uniquifier*, *enum sysinit\_sub\_id subsystem*, *enum sysinit\_elem\_order order*, *sysinit\_cfunc\_t func*, *const void \*ident*);

## DESCRIPTION

**SYSINIT** is a mechanism for scheduling the execution of initialization and teardown routines. This is similar to init and fini routines with the addition of explicit ordering metadata. It allows runtime ordering of subsystem initialization in the kernel as well as kernel modules (KLDs).

The **SYSINIT**() macro creates a *struct* *sysinit* and stores it in a startup linker set. The *struct* *sysinit* type as well as the subsystem identifier constants (SI\_SUB\_\*) and initialization ordering constants (SI\_ORDER\_\*) are defined in ⟨sys/kernel.h⟩:

```
struct sysinit {
	enum sysinit_sub_id subsystem;	/* subsystem identifier*/
	enum sysinit_elem_order	order;	/* init order within subsystem*/
	SLIST_ENTRY(sysinit) next;	/* singly-linked list */
	sysinit_cfunc_t func;		/* function             */
	const void	*udata;		/* multiplexer/argument */
};
```

The **SYSINIT**() macro takes a *uniquifier* argument to identify the particular function dispatch data, the *subsystem* type of startup interface, the subsystem element *order* of initialization within the subsystem, the *func* function to call, and the data specified in *ident* argument to pass the function.

The **SYSUNINIT**() macro behaves similarly to the **SYSINIT**() macro except that it adds the data to a shutdown linker set.

The startup linker set for the kernel is scanned during boot to build a sorted list of initialization routines. The initialization routines are then executed in the sorted order. The *subsystem* is used as the primary key and is sorted in ascending order. The *order* is used as the secondary key and is sorted in ascending order. The relative order of two routines that have the same *subsystem* and *order* is undefined.

The startup linker sets for modules that are loaded together with the kernel by the boot loader are scanned during the SI\_SUB\_KLD subsystem initialization. These modules' initialization routines are sorted and merged into the kernel's list of startup routines and are executed during boot along with the kernel's initialization routines. Note that this has the effect that any initialization routines in a kernel module that are scheduled earlier than SI\_SUB\_KLD are not executed until after SI\_SUB\_KLD during boot.

The startup linker set for a kernel module loaded at runtime via [kldload(2)](/kldload/2.md) is scanned, sorted, and executed when the module is loaded.

The shutdown linker set for a kernel module is scanned, sorted, and executed when a kernel module is unloaded. The teardown routines are sorted in the reverse order of the initialization routines. The teardown routines of the kernel and any loaded modules are **not** executed during shutdown.

## EXAMPLES

This example shows the SYSINIT which displays the copyright notice during boot:

```
static void
print_caddr_t(void *data)
{
	printf("%s", (char *)data);
}
SYSINIT(announce, SI_SUB_COPYRIGHT, SI_ORDER_FIRST, print_caddr_t,
    copyright);
```

## SEE ALSO

[kld(4)](/kld/4.md), [DECLARE\_MODULE(9)](/DECLARE_MODULE/9.md), [DEV\_MODULE(9)](/DEV_MODULE/9.md), [DRIVER\_MODULE(9)](/DRIVER_MODULE/9.md), [MTX\_SYSINIT(9)](/MTX_SYSINIT/9.md), [SYSCALL\_MODULE(9)](/SYSCALL_MODULE/9.md)

## HISTORY

The **SYSINIT** framework first appeared in FreeBSD 2.2.

## AUTHORS

The **SYSINIT** framework was written by Terrence Lambert ⟨*terry@FreeBSD.org*⟩.

This manual page was written by Hiten Pandya ⟨*hmp@FreeBSD.org*⟩.