Create a software shutdown command

[ethanmw]

Currently the only shutdown method is a hardware power-off, which could result in corrupted filesystems once we start using R/W filesystems, especially after we add support for large files.

Adding ACPI support might be complicated, but we should at least have a shell shutdown command

[dthain]

That's a good point -- regardless of whether we can physically accomplish a shutdown, the kernel should have a sequence for safely flushing buffers, etc before the shutdown happens.

[dsmith47]

I can't comment on the process for buffer cleaning, but the ACPI interface is a slightly complicated (but already solved) coding process. Does this serve any of our goals?
https://forum.osdev.org/viewtopic.php?t=16990

[dthain]

If you can find some code that reliably does it right out of the box, great.
However, the comments on that thread seem to suggest that it isn't fully working yet...

[dthain]

The main point of this issue is not to implement the actual power shutdown, but rather to bring the kernel to a quiescent state by halting all processes, flushing the buffer cache, etc. Then it is safe to pull the plug, even if power-down is not implemented.