Required disk checking
Many modern operating systems expect that the user is not writing to the hard drive at the time that a computer has its power turned off. Many of them even don't want the partitions mounted in a writable format. In practice, this often means that the system should not be running normally. Instead, the system should go through an official “shutdown” process, which allows the system to make sure that the disk volume layout has no unfinished work.
This information may not be needed for people who haven't encountered an improper reboot. However, since this can be a real show-stopper, here are some instructions in case this does come up.
As a quick side note, this is not true of all operating systems.
Historically (during the 1980's and early 1990's, become less true during the late 1990's), MS-DOS was a very popular platform, and that platform did not have this problem very much, unless using
's write caching (although flushing the disk cache, with “
”, would reduce the likelihood of such problems).
Such stability isn't necessarily archaic; NanoBSD's home page mentions this feature: “Everything is read-only at run-time — It is safe to pull the power-plug. There is no necessity to run
(8) after a non-graceful shutdown of the system.” That's not an obscure recommendation by somebody that is particularly prone to take risks. It is listed as one of the official features of the operating system. The operating system was, quite simply, properly designed to be able to survive a power outage without risking corruption of critical data.