Linux Bootup

Linux startup sequence in 2.4.x

This page illustrates the Linux bootup in 2.4 kernels. Depending of the exact version there may be some slight differences. Linux 2.6 differs quite a bit.

   kernel_entry() - arch/mips/kernel/head.S
      set stack;
      prepare argc/argp/envp;
      jal init_arch - arch/mips/kernel/setup.c
           cpu_probe() -
           prom_init(...) - arch/mips/ddb5074/prom.c
           loadmmu()
           start_kernel()  - init/main.c
                   setup_arch(&commaind_line); - arch/mips/kernel/setup.c
                           ddb_setup()         - arch/mips/ddb5074/setup.c
                   parse_options(command_line);
                   trap_init();
                   init_IRQ();                 - arch/mips/kernel/irq.c
                   sched_init();
                   softirq_init();
                   time_init();
                           if (board_time_init) board_time_init();
                           set xtime by calling rtc_get_time();
                           pick appropriate do_gettimeoffset()
                           board_timer_setup(&timer_irqaction);
                   console_init();
                   init_modules();
                   kmem_cache_init();
                   sti();                  /* interrupt first open */
                   calibrate_delay();
                   mem_init();
                   kmem_cache_sizes_init();
                   pgtable_cache_init();
                   fork_init();
                   proc_caches_init();
                   vfs_caches_init();
                   buffer_init();
                   page_cache_init();
                   signals_init();
                   smp_init();
                   kernel_thread(init, ...)
                   cpu_idle();

   init() - init/main.c
     - lock_kernel();
       do_basic_setup();
         - [MTRR] mtrr_init();
           [SYSCTL] sysctl_init();
           [S390] s390_init_machine_check();
           [ACPI] acpi_init();
           [PCI] pci_init();
           [SBUS] sbus_init();
           [PPC] ppc_init();
           [MCA] mca_init();
           [ARCH_ACORN] ecard_init();
           [ZORRO] zorro_init();
           [DIO] dio_init();
           [MAC] nubus_init();
           [ISAPNP] isapnp_init();
           [TC] tc_init();
           sock_init();
           start_context_thread();
           do_initcalls();
           [IRDA] irda_proto_init();
           [IRDA] irda_device_init();
           [PCMCIA] init_pcmcia_ds();

       prepare_namespace();
       free_initmem();
       unlock_kernel();

       files = current->files;
       if(unshare_files())
               panic("unshare");
       put_files_struct(files);

       if (open("/dev/console", O_RDWR, 0) < 0)
                   printk("Warning: unable to open an initial console.\n");
       (void) dup(0);
       (void) dup(0);

       if (execute_command)
                   run_init_process(execute_command);
       run_init_process("/sbin/init");
       run_init_process("/etc/init");
       run_init_process("/bin/init");
       run_init_process("/bin/sh");

       panic("No init found.  Try passing init= option to kernel.");