Recognizing Other Critical Problems
Sometimes it's obvious that you need to go into “emergency mode” and try to preserve your data and rescue your system—for example, if you suffer a complete hard drive failure or if you are unable to boot Linux at all. There are, however, two times when it is desirable to preemptively take drastic action to save your system even though your system still appears to be mostly functional:
Situations in which your hard drive is displaying symptoms of file system corruption or approaching failure
Situations in which you can determine that your Linux system might have fallen victim to network hacking or Trojan horse or worm programs
Left unchecked, either of these situations can lead to eventual unexpected downtime, ...