Build a "hello world" program.

  #include <stdio.h>
  #include <unistd.h>

  int main(int argc, char *argv[])
  {
    printf("Hello world!\n");
    sleep(9999999);
    return 0;
  }

  gcc hello.c -o hello

  ./hello

  Sleep instead of returning avoids "kernel panic, tried to kill init" later.