On Mon, 24 Dec 2001, Terry Houle wrote:

> Probably a dump question but I got some Linux decals that say
> "Warning:Turning off the power or pressing reset switch could lose contents
> of hard drive.  If you must restart this system, please get help or use
> Ctrl-Alt-Del".  My question is if Linux is more of a problem than Windows if
> shutdown improperly?  Sometimes in Windows even the  Ctrl-Alt-Del won't work
> and I have to reset.  I know it is not good but the only option in Windows
> when it hangs up.
> I know I will get the Linux is not Windows, but wondering if there is
> difference?

Before I get too far into this, C-A-D on a Linux box just
invokes "shutdown -h now" AKA "init 0".

In addition, I did a hard powerdown reboot on my system about
2 hours ago because of an apparent IDE-SCSI bug that hung my system
beyond my patience to deal with it. Everything recovered cleanly,
as I expected it to, but I normally shutdown using "init 0".

Now the explanation for the warning (assuming Ext2fs):

This is largely due to disk caching in memory.
If you kill the power without flushing the buffers
to disk you can end up with an inconsistent filesystem.

Generally the fsck run at boot time can clean up properly, but
this takes time and only works about 99% of the time. So if
you kill the power a lot, you are likely to kill your system
eventually. Running "sync" before killing the power improves
your odds, but if you are going to that much trouble you might
as well do the proper shutdown.

On the plus side, I have never had a proper shutdown fail
in almost 10 years of using Linux, but I have seen people's
Windows 98 boxes fail to shutdown cleanly all the time.
In addition, the recovery rate I saw with scandisk on Win3.1
was significantly less than the 99%+ rate I expect with ext2fsck.

In conclusion, I would say that the warning is mostly
due to the higher expectation of Linux users that they
will be able to avoid OS reinstalls (and indeed most maintenance),
if the system is merely treated properly.

-- 
Daniel Taylor