Power management/Suspend and hibernate: Difference between revisions
(→Configure the initramfs: try to make this clearer, see Talk:Power management/Suspend and hibernate#systemd hook) |
(Partially undo revision 378282 by Kynikos (talk) sorry, that was inaccurate, trying again, see Talk:Power management/Suspend and hibernate#systemd hook) |
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=== Configure the initramfs === | === Configure the initramfs === | ||
* When an [[initramfs]] with the {{ic|base}} hook is used, which is the default, the {{ic|resume}} hook is required in {{ic|/etc/mkinitcpio.conf}}. Whether by label or by UUID, the swap partition is referred to with a udev device node, so the {{ic|resume}} or {{ic|systemd}} hook must go ''after'' the {{ic|udev}} hook. This example was made starting from the default hook configuration: | |||
:{{bc|1=HOOKS="base udev '''resume''' autodetect modconf block filesystems keyboard fsck"}} | |||
:{{Note|[[LVM]] users should add the {{ic|resume}} hook after {{ic|lvm2}}.}} | |||
Rebuild the initramfs for these changes to take effect: | :Rebuild the initramfs for these changes to take effect: | ||
:{{bc|# mkinitcpio -p linux}} | |||
{{Note|If you use a custom kernel, then you might have to change the value of the {{ic|-p}} option.}} | :{{Note|If you use a custom kernel, then you might have to change the value of the {{ic|-p}} option.}} | ||
* When an initramfs with the {{ic|systemd}} hook is used, a resume mechanism is already provided, and no further hooks need to be added. | |||
== Troubleshooting == | == Troubleshooting == |
Revision as of 01:59, 14 June 2015
Currently there are three methods of suspending available: suspend to RAM (usually called just suspend), suspend to disk (usually known as hibernate), and hybrid suspend (sometimes aptly called suspend to both):
- Suspend to RAM method cuts power to most parts of the machine aside from the RAM, which is required to restore the machine's state. Because of the large power savings, it is advisable for laptops to automatically enter this mode when the computer is running on batteries and the lid is closed (or the user is inactive for some time).
- Suspend to disk method saves the machine's state into swap space and completely powers off the machine. When the machine is powered on, the state is restored. Until then, there is zero power consumption.
- Suspend to both method saves the machine's state into swap space, but does not power off the machine. Instead, it invokes usual suspend to RAM. Therefore, if the battery is not depleted, the system can resume from RAM. If the battery is depleted, the system can be resumed from disk, which is much slower than resuming from RAM, but the machine's state has not been lost.
There are multiple low level interfaces (backends) providing basic functionality, and some high level interfaces providing tweaks to handle problematic hardware drivers/kernel modules (e.g. video card re-initialization).
Low level interfaces
Though these interfaces can be used directly, it is advisable to use some of high level interfaces to suspend/hibernate. Using low level interfaces directly is significantly faster than using any high level interface, since running all the pre- and post-suspend hooks takes time, but hooks can properly set hardware clock, restore wireless etc.
kernel (swsusp)
The most straightforward approach is to directly inform the in-kernel software suspend code (swsusp) to enter a suspended state; the exact method and state depends on the level of hardware support. On modern kernels, writing appropriate strings to /sys/power/state
is the primary mechanism to trigger this suspend.
See kernel documentation for details.
uswsusp
The uswsusp ('Userspace Software Suspend') is a wrapper around the kernel's suspend-to-RAM mechanism, which performs some graphics adapter manipulations from userspace before suspending and after resuming.
See main article Uswsusp.
tuxonice
TuxOnIce is a fork of the kernel implementation of suspend/hibernate that provides kernel patches to improve the default implementation. It requires a custom kernel to achieve this purpose.
See main article TuxOnIce.
High level interfaces
systemd
systemd provides native commands for suspend, hibernate and a hybrid suspend, see Power management#Power management with systemd for details. This is the default interface used in Arch Linux.
See Power management#Sleep hooks for additional information on configuring suspend/hibernate hooks. Also see man systemctl
, man systemd-sleep
, and man systemd.special
.
pm-utils
pm-utils is a set of shell scripts that encapsulate the backend's suspend/hibernate functionality. It comes with a set of pre- and post-suspend tweaks and various hooks to customize the process.
See main article pm-utils.
Hibernation
In order to use hibernation, you need to create swap partition or swap file. See Swap for details.
About swap partition/file size
Even if your swap partition is smaller than RAM, you still have a big chance of hibernating successfully. According to kernel documentation:
/sys/power/image_size
controls the size of the image created by the suspend-to-disk mechanism. It can be written a string representing a non-negative integer that will be used as an upper limit of the image size, in bytes. The suspend-to-disk mechanism will do its best to ensure the image size will not exceed that number. However, if this turns out to be impossible, it will try to suspend anyway using the smallest image possible. In particular, if "0" is written to this file, the suspend image will be as small as possible. Reading from this file will display the current image size limit, which is set to 2/5 of available RAM by default.
You may either decrease the value of /sys/power/image_size
to make the suspend image as small as possible (for small swap partitions), or increase it to possibly speed up the hibernation process.
Required kernel parameters
The kernel parameter resume=swap_partition
has to be used. Either the name the kernel assigns to the partition or its UUID can be used as swap_partition
. For example:
resume=/dev/sda1
resume=UUID=4209c845-f495-4c43-8a03-5363dd433153
resume=/dev/mapper/archVolumeGroup-archLogicVolume
-- example if using LVM
Generally, the naming method used for the resume
parameter should be the same as used for the root
parameter.
The configuration depends on the used boot loader, refer to Kernel parameters for details.
Hibernation into swap file
Using a swap file instead of a swap partition requires an additional kernel parameter resume_offset=swap_file_offset
.
The value of swap_file_offset
can be obtained by running filefrag -v swap_file
, the output is in a table format and the required value is located in the first row of the physical_offset
column. For example:
# filefrag -v /swapfile
Filesystem type is: ef53 File size of /swapfile is 4294967296 (1048576 blocks of 4096 bytes) ext: logical_offset: physical_offset: length: expected: flags: 0: 0.. 0: 38912.. 38912: 1: 1: 1.. 22527: 38913.. 61439: 22527: unwritten 2: 22528.. 53247: 899072.. 929791: 30720: 61440: unwritten ...
In the example the value of swap_file_offset
is 38912
.
swap_file_offset
can also be obtained by running swap-offset swap_file
. The swap-offset binary is provided by package uswsusp-gitAUR.- The
resume
kernel parameter specifies the device of the partition that contains the swap file, not swap file itself! The parameterresume_offset
informs the system where the swap file starts on the resume device. - If using uswsusp, then these two parameters have to be provided in
/etc/suspend.conf
via the keysresume device
andresume offset
.
Configure the initramfs
- When an initramfs with the
base
hook is used, which is the default, theresume
hook is required in/etc/mkinitcpio.conf
. Whether by label or by UUID, the swap partition is referred to with a udev device node, so theresume
orsystemd
hook must go after theudev
hook. This example was made starting from the default hook configuration:
HOOKS="base udev resume autodetect modconf block filesystems keyboard fsck"
- Rebuild the initramfs for these changes to take effect:
# mkinitcpio -p linux
- Note: If you use a custom kernel, then you might have to change the value of the
-p
option.
- When an initramfs with the
systemd
hook is used, a resume mechanism is already provided, and no further hooks need to be added.
Troubleshooting
ACPI_OS_NAME
You might want to tweak your DSDT table to make it work. See DSDT article
VAIO Users
Add acpi_sleep=nonvs kernel flag to your loader, and you are done!
Suspend/hibernate doesn't work
There have been many reports about the screen going black without easily viewable errors or the ability to do anything when going into and coming back from suspend and/or hibernate. These problems have been seen on both laptops and desktops. This is not an official solution, but switching to an older kernel, especially the LTS-kernel, will probably fix this.
Wake-on-LAN
If Wake-on-LAN is active, the network interface card will consume power even if the computer is hibernated.