Why is make printing "make: Nothing to be done for `all'."? [duplicate]

Question

This is a "Hello.c" module and "Makefile". After executing make from the woking directory I get the following message:

make: Nothing to be done for `all'.

This is the "Hello.c" file:

#include <linux/module.h>    // included for all kernel modules
#include <linux/kernel.h>    // included for KERN_INFO
#include <linux/init.h>      // included for __init and __exit macros

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Lakshmanan");
MODULE_DESCRIPTION("A Simple Hello World module");

static int __init hello_init(void) {
  printk(KERN_INFO "Hello world!\n");
  return 0;    // Non-zero return means that the module couldn't be
}

static void __exit hello_cleanup(void) {
    printk(KERN_INFO "Cleaning up module.\n");
}   

module_init(hello_init); 
module_exit(hello_cleanup);

And "Makefile":

obj-m += hello.o

all:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

I tried all suggestions and I got this in the terminal:

root@stupid-HP:/home/stupid/cpz/module$ pwd
/home/stupid/cpz/module
root@stupid-HP:/home/stupid/cpz/module$ ls
hello.c  Makefile
root@stupid-HP:/home/stupid/cpz/module$ make
make: Nothing to be done for `all'.
root@stupid-HP:/home/stupid/cpz/module$ make clean
make: Nothing to be done for `clean'.
root@stupid-HP:/home/stupid/cpz/module$ make clean all
make: Nothing to be done for `clean'.
make: Nothing to be done for `all'.
root@stupid-HP:/home/stupid/cpz/module$ ls
hello.c  Makefile
root@stupid-HP:/home/stupid/cpz/module$ make
make: Nothing to be done for `all'.
root@stupid-HP:/home/stupid/cpz/module$ vi hello.c  # modified again
root@stupid-HP:/home/stupid/cpz/module$ make clean
make: Nothing to be done for `clean'.
root@stupid-HP:/home/stupid/cpz/module$ make
make: Nothing to be done for `all'.

Answer 1

Make works on the base of time stamps. If you alter some of your source files Make compile them and built the image accordingly. If you do not change source file then compiler has nothing to do with your project. make does not work like gcc to compile every time whether new build is needed or not. This is one of many advantages of using make for your project.

Answer 2

You should remove space in your Makefile. In makefile, only use tab.

I tested your code again, and it works with tab

Answer 3

1. make clean and then make again
2. check for spaces and tabs as per make file format
3. Verify the Path of the kernel libraries

Answer 4

Compiler is simply telling you that your code was already compiled and there are no changes in your code (it is up to date), then it does not compile. Is a builtin feature of compilers, if there are no changes in source code file, compilers do not waste time.

Use make clean before to make or modify Hello.c and Build your project.