[PATCH] UHCI: Work around old Intel bug

[deliverable/linux.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.
 *
 * If you have any filesystems on USB devices mounted before suspend,
 * they won't be accessible after resume and you may lose data, as though
 * you have unplugged the USB devices with mounted filesystems on them
 * (see the FAQ below for details).

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 have SATA disks, you'll need recent kernels with SATA suspend
support. For suspend and resume to work, make sure your disk drivers
are built into kernel -- not modules. [There's way to make
suspend/resume with modular disk drivers, see FAQ, but you probably
should not do that.]

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

echo N > /sys/power/image_size

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


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