On Mon, May 11, 1998 at 01:02:40AM -0400, Thomas F. Maher, Jr. wrote:
> What happens if you do shut off Linux by killing the power? What
> drastically goes wrong?
In general, Unix systems don't like this. Two kinds of things tend
to go wrong:
1. Any background process (daemon) that's running may get caught in
the middle of an operation and not get the opportunity to exit cleanly
and save its state. For example, if you just happen to catch sendmail
as it's delivering a message right after it drops it in somebody's
mailbox but right before it deletes it from the queue (a few microseconds
later) you may wind up with two copies of the message.
2. More likely: filesystem problems. Unix filesystems are highly
optimized -- one of the reasons there are no defragmenters is that
they're not needed -- but the price for this is that state information
has to be kept in a consistent manner in multiple places. If you catch
the kernel in a state where it's deleted a file but not all the references
to it, for example, then your filesystem will be in an inconsistent state
when you reboot the machine.
That said, about 99% of the time, "fsck" -- which gets run when you boot
up -- will fix things. Fsck is one of the smarter Unix programs, designed
to deal with these kinds of errors, and it can cope with amazing amounts
of damage. But it's best to shut down cleanly and not leave it a huge
pile of work to do on your next boot.
---Rsk
Rich Kulawiec
[EMAIL PROTECTED]
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