1. Introduction

1.1 What is software suspend ?

Software suspend is the ability to freeze the kernel state and dump it on disk, then restore it upon resuming. This allows to completely stop a computer for a long period while keeping an internal session opened. In modern laptops, suspension is no more done by the BIOS, even the unbuggy ones. It uses ACPI and ask the operating system to do most of the job. If you can't satisfy yourself with standby mode (suspension to RAM) because you leave your computer in suspension mode for too long a time, then you have to suspend on disk.

1.2 Copyright (skip this if you're in a hurry)

Copyright (c) 2002, 2003 by Florent Chabaud. Please freely copy and distribute (sell or give away) this document in any format. Send any corrections and comments to the document maintainer. You may create a derivative work and distribute it provided that you:

1. If it's not a translation: Email a copy of your derivative work to the author(s) and maintainer (could be the same person).
2. License the derivative work in the spirit of this license or use GPL. Include a copyright notice and at least a pointer to the license used.
3. Give due credit to previous authors and major contributors.

1.3 Why I wrote this ?

Software suspend has a long story, but for a long time it was considered as alpha. This is mainly due to the fact that suspension has to deal with a lot of aspects in kernel. It is therefore difficult to follow the kernel development (for instance transition from 2.2 to 2.4 was not straightforward). The patch can now be considered in a beta stage since it seems to work rather reliably and a lot of bugs have been fixed. This is perhaps a little too optimistic but we need some beta-testers ;-) If you have a mono-processor machine with Pentium like CPU and ide disks, it is very likely that swsusp will perform correctly. However, installing, configuring and using software suspension is not straightforward, since it involves recompiling the kernel and setting some boot parameters. Hence, as long as software suspension will not be taken in account by modern linux distributions (and probably even after that :-) a mini-howto may be found useful.