Today (28-Dec) is Linus Torvald, Linux creator’s birthday and I wanted to share with you an easter egg hidden in the Linux reboot() system call.
From man page of reboot Link to heading
SYNOPSIS:
--------
#include <unistd.h>
#include <linux/reboot.h>
int reboot(int magic, int magic2, int cmd, void *arg);
DESCRIPTION:
------------
The reboot() call reboots the system, or enables/disables the reboot
keystroke (abbreviated CAD, since the default is Ctrl-Alt-Delete; it
can be changed using loadkeys(1)).
This system call will fail (with EINVAL) unless magic equals
LINUX_REBOOT_MAGIC1 (that is, 0xfee1dead) and magic2 equals
LINUX_REBOOT_MAGIC2 (that is, 672274793). However, since 2.1.17 also
LINUX_REBOOT_MAGIC2A (that is, 85072278) and since 2.1.97 also
LINUX_REBOOT_MAGIC2B (that is, 369367448) and since 2.5.71 also
LINUX_REBOOT_MAGIC2C (that is, 537993216) are permitted as values for
magic2. (The hexadecimal values of these constants are meaningful.)
You can find these variables and their values in the reboot.h header file in the Linux kernel source repository.
root@server7:~/linux# grep 'LINUX_REBOOT_MAGIC' include/uapi/linux/reboot.h
#define LINUX_REBOOT_MAGIC1 0xfee1dead
#define LINUX_REBOOT_MAGIC2 672274793
#define LINUX_REBOOT_MAGIC2A 85072278
#define LINUX_REBOOT_MAGIC2B 369367448
#define LINUX_REBOOT_MAGIC2C 537993216
So, there are few magic numbers LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, LINUX_REBOOT_MAGIC2A, LINUX_REBOOT_MAGIC2B, LINUX_REBOOT_MAGIC2C in Linux, which are needed as the argument of the reboot system call. The values of these variables are mentioned in the man page itself. What are these numbers anyway? Well, it turns out these are not just random numbers. Let’s see what we can find out.
Converting these numbers into hexadecimal reveals something interesting. In case you are confused, the printf "%x\n" 1234 will convert 1234 into hexadecimal.
root@server7:~/linux# printf "%x\n" 672274793
28121969 ( 28-12-1969) - Birthday of Linus
root@server7:~/linux# printf "%x\n" 85072278
5121996 (5-12-1996) - Birthday of Patricia Miranda, Linus’ first daughter
root@server7:~/linux# printf "%x\n" 369367448
16041998 (16-04-1998) - Birthday of Daniela Yolanda, Linus’ second daughter
root@server7:~/linux# printf "%x\n" 537993216
20112000 (20-11-2000) - Birthday of Celeste Amanda, Linus’ third daughter.
I mean, that’s kinda cool. :D Oh, and, Happy Birthday, Linus. Thank you for giving us Linux. And git. ;)