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title: Kernel compile "Hello world"
# Kernel compile "Hello world"
Compile minimal linux kernel module.
## Files
You need to create to files __Makefile__ and __hello_world.c__.
__Makefile__
```Makefile
obj-m += hello_world.o
KDIR ?= /lib/modules/$(shell uname -r)/build
all:
make -C $(KDIR) M=$(PWD) modules
clean:
make -C $(KDIR) M=$(PWD) clean
```
__hello_world.c__
```c
//http://www.tldp.org/LDP/lkmpg/2.4/html/c147.htm
#include <linux/module.h> /* Needed by all modules */
#include <linux/kernel.h>
int hello_world_init( void )
{
printk(KERN_DEBUG "Hello World!\n");
return 0;
}
void hello_world_exit( void )
{
printk(KERN_DEBUG "Exit Hello World!\n");
}
module_init( hello_world_init );
module_exit( hello_world_exit );
MODULE_LICENSE("GPL");
```
## Compile
Now if you havent done so ... install kernel headers of kernel that your system have now. And everything should be there.
```sh
make
```
## Load module
```sh
sudo insmod hello_world.ko
```
check that module is running
```sh
lsmod | grep hello
```
## Unload module
```sh
rmmod hello_world
```
### Install kernel headers raspbian
RaspberryPi4 ARMv8
```bash
sudo apt-get install raspberrypi-kernel-headers
```
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