Create a Linux module

1. vi simple-lmk.c

#include 

/* Defines the license for this LKM */
MODULE_LICENSE("GPL");

/* Init function called on module entry */
int my_module_init( void )
{
printk(KERN_INFO "my_module_init called.  Module is now loaded.\n");
return 0;
}

/* Cleanup function called on module exit */
void my_module_cleanup( void )
{
printk(KERN_INFO "my_module_cleanup called.  Module is now unloaded.\n");
return;
}

/* Declare entry and exit functions */
module_init( my_module_init );
module_exit( my_module_cleanup );

2. vi Makefile

obj-m += simple-lkm.o

3. build

make -C /usr/src/linux-`uname -r` SUBDIRS=$PWD modules

4. insert module
insmod simple-lkm.ko

5. check module
lsmod

6. check print message
dmesg | tail -5

7. remove module
rmmod simple-lkm