[PATCH] uml: compilation fix when MODE_SKAS disabled

[mirror_ubuntu-artful-kernel.git] / Documentation / power / swsusp.txt

Some warnings, first.

 * BIG FAT WARNING *********************************************************
 *
 * If you touch anything on disk between suspend and resume...
 *				...kiss your data goodbye.
 *
 * If you do resume from initrd after your filesystems are mounted...
 *				...bye bye root partition.
 *			[this is actually same case as above]
 *
 * If you have unsupported (*) devices using DMA, you may have some
 * problems. If your disk driver does not support suspend... (IDE does),
 * it may cause some problems, too. If you change kernel command line
 * between suspend and resume, it may do something wrong. If you change
 * your hardware while system is suspended... well, it was not good idea;
 * but it will probably only crash.
 *
 * (*) suspend/resume support is needed to make it safe.

You need to append resume=/dev/your_swap_partition to kernel command
line. Then you suspend by

echo shutdown > /sys/power/disk; echo disk > /sys/power/state

. If you feel ACPI works pretty well on your system, you might try

echo platform > /sys/power/disk; echo disk > /sys/power/state

If you want to limit the suspend image size to N megabytes, do

echo N > /sys/power/image_size

before suspend (it is limited to 500 MB by default).

Encrypted suspend image:
------------------------
If you want to store your suspend image encrypted with a temporary
key to prevent data gathering after resume you must compile
crypto and the aes algorithm into the kernel - modules won't work
as they cannot be loaded at resume time.


Article about goals and implementation of Software Suspend for Linux
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~