Definitions

• Primary server:
  Server containing website data and md5sums and script p
• website data:
  anything stored at /var/www/html
• backup server:
  Server containing script s
• md5sums:
  Contains md5sums of all files in website data
• t:
  monitor interval

Steps

1. Start execution of p first.
2. p sees no md5sums, ∴ generates one. (p is capable of generating md5sums)
3. Start execution of s
4. s connects to p
5. s sees no md5sums with itself, ∴ requests one.
6. md5sums transferred p ⇨ s
7. Wait for t units of time.
8. p resends md5sums to s
9. • if new file received and all sums (except sums marked for change) in both files (old and new) match:
     ALL OK.
     Replace old md5sums with new.
   • else:

   Unauthorized change detected:

10. • if unauthorized change detected:
      send emails, raise errors, evacuate city.
    • else:
      Go to step 7