Power management/Suspend and hibernate
Currently there are three methods of suspending available:
- Suspend to RAM (aka suspend, aka sleep)
- The S3 sleeping state as defined by ACPI. Works by cutting off 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 (aka hibernate)
- The S4 sleeping state as defined by ACPI. 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
- A hybrid of the aforementioned methods, sometimes called hybrid suspend. 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 the 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.
High level interfaces
The end goal of these packages is to provide binaries/scripts that can be invoked to perform suspend/hibernate. Actually hooking them up to power buttons or menu clicks or laptop lid events is usually left to other tools. To automatically suspend/hibernate on certain power events, such as laptop lid close or battery depletion percentage, you may want to look into running Acpid.
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 systemctl(1), systemd-sleep(8), and systemd.special(7).
Hibernation
In order to use hibernation, you need to create a swap partition or file. You will need to point the kernel to your swap using the resume= kernel parameter, which is configured via the boot loader. You will also need to configure the initramfs. This tells the kernel to attempt resuming from the specified swap in early userspace. These three steps are described in detail below.
- See Dm-crypt/Swap encryption#With suspend-to-disk support when using encryption.
- linux-hardened does not support hibernation, see FS#63648.
About swap partition/file size
Even if your swap partition is smaller than RAM, you still have a big chance of hibernating successfully. See "image_size" in the kernel documentation for information on the image_size sysfs(5) pseudo-file.
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. For systems with a large amount of RAM, smaller values may drastically increase the speed of resuming a hibernating system. See systemd#systemd-tmpfiles - temporary files to make this change persistent.
The suspend image cannot span multiple swap partitions and/or swap files. It must fully fit in one swap partition or one swap file.[1]
Required kernel parameters
The kernel parameter resume=swap_device must be used. Any of the persistent block device naming methods can be used as swap_device. For example:
resume=UUID=4209c845-f495-4c43-8a03-5363dd433153resume="PARTLABEL=Swap partition"-
resume=/dev/archVolumeGroup/archLogicalVolume-- if swap is on a LVM logical volume
The kernel parameters will only take effect after rebooting. To be able to hibernate right away, obtain the volume's major and minor device numbers from lsblk and echo them in format major:minor to /sys/power/resume. If using a swap file, additionally echo the resume offset to /sys/power/resume_offset.[2]
For example, if the swap device is 8:3:
# echo 8:3 > /sys/power/resume
Or when hibernating to a swap file, if the swap file is on volume 8:2 and has the offset 38912:
# echo 8:2 > /sys/power/resume # echo 38912 > /sys/power/resume_offset
Hibernation into swap file
Using a swap file requires also setting the resume=swap_device and additionally a resume_offset=swap_file_offset kernel parameters. See the kernel documentation.
swap_device is the volume where the swap file resides and it follows the same format as for the root parameter. 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 the first 38912 with the two periods.
- The following command may be used to identify
swap_device:findmnt -no UUID -T /swapfile - The following command may be used to identify
swap_file_offset:filefrag -v /swapfile | awk '$1=="0:" {print substr($4, 1, length($4)-2)}' - The value of
swap_file_offsetcan also be obtained by runningswap-offset swap_file. The swap-offset binary is provided within the set of tools uswsusp. If using this method, then these two parameters have to be provided in/etc/suspend.confvia the keysresume deviceandresume offset. No reboot is required in this case.
- For a stacked block device such as an encrypted container (LUKS), RAID or LVM, the
resumeparameter must point to the unlocked/mapped device that contains the file system with the swap file. - If the swap file is in
/home/, systemd-logind will not be able to determine its size and thus will prevent hibernation with the following message:Failed to hibernate system via logind: Not enough swap space for hibernation. See systemd issue 15354 for two workarounds.
Hibernation into swap file on Btrfs
The resume_offset number can be computed using the tool btrfs_map_physical.c. Do not try to use the filefrag tool, on Btrfs the "physical" offset you get from filefrag is not the real physical offset on disk; there is a virtual disk address space in order to support multiple devices. [3]
Download or copy the tool btrfs_map_physical.c into a file named btrfs_map_physical.c, then compile it,
$ gcc -O2 -o btrfs_map_physical btrfs_map_physical.c
and run it. An example output is shown below.
# ./btrfs_map_physical /path/to/swapfile
FILE OFFSET EXTENT TYPE LOGICAL SIZE LOGICAL OFFSET PHYSICAL SIZE DEVID PHYSICAL OFFSET 0 regular 4096 2927632384 268435456 1 4009762816 4096 prealloc 268431360 2927636480 268431360 1 4009766912 268435456 prealloc 268435456 3251634176 268435456 1 4333764608 536870912 prealloc 268435456 3520069632 268435456 1 4602200064 805306368 prealloc 268435456 3788505088 268435456 1 4870635520 1073741824 prealloc 268435456 4056940544 268435456 1 5139070976 1342177280 prealloc 268435456 4325376000 268435456 1 5407506432 1610612736 prealloc 268435456 4593811456 268435456 1 5675941888
Note the the first physical offset returned by this tool. In this example, we use 4009762816. Also note the pagesize that can be found with getconf PAGESIZE.
To compute the resume_offset value, divide the physical offset by the pagesize. In this example, it is 4009762816 / 4096 = 978946.
Hibernation into a thinly-provisioned LVM volume
Hibernation into a thinly-provisioned LVM volume is possible, but you have to make sure that the volume is fully allocated. Otherwise resuming from it will fail, see FS#50703.
You can fully allocate the LVM volume by simply filling it with zeros. E.g.:
# dd if=/dev/zero of=/dev/vg0/swap bs=1M status=progress
To verify the volume is fully allocated, you can use:
# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert swap vg0 Vwi-aot--- 10.00g pool 100
A fully allocated volume will show up as having 100% data usage.
discard in /etc/fstab and the -d/--discard option of swapon. Otherwise the used space will be deallocated.Configure the initramfs
- When an initramfs with the
basehook is used, which is the default, theresumehook is required in/etc/mkinitcpio.conf. Whether by label or by UUID, the swap partition is referred to with a udev device node, so theresumehook must go after theudevhook. This example was made starting from the default hook configuration:
HOOKS=(base udev autodetect keyboard modconf block filesystems resume fsck)
- Remember to regenerate the initramfs for these changes to take effect.
- When an initramfs with the
systemdhook is used, a resume mechanism is already provided, and no further hooks need to be added.
Intel Rapid Start Technology (IRST)
With Intel Rapid Start Technology (IRST) enabled, resuming from a deep sleep takes "a few seconds longer than resuming from S3 but is far faster than resuming from hibernation".
Many Intel-based systems have firmware support for IRST but require a special partition on an SSD (rather than an HDD). OEM deployments of Windows may already have a preexisting IRST partition which can be retained during the Arch Linux installation process (rather than wiping and repartitioning the whole SSD). It should show up as an unformatted partition equal in size to the system's RAM.
However, if you intend to wipe and repartition the whole drive (or have already done so), then the IRST partition must be recreated if you also plan on using the technology. This can be done by creating an empty partition equal in size to the system's RAM and by setting its partition type to GUID D3BFE2DE-3DAF-11DF-BA40-E3A556D89593 for a GPT partition or ID 0x84 for an MBR partition. You may also need to enable support for IRST in your system's firmware settings.
The duration of the IRST hibernation process (i.e., copying the "entire contents of RAM to a special partition") is dependant on the system's RAM size and SSD speed and can thus take 20–60 seconds. Some systems may indicate the process's completion with an LED indicator, e.g., when it stops blinking.
See also the general Q&A and user guides for Intel Rapid Start Technology.
Troubleshooting
ACPI_OS_NAME
You might want to tweak your DSDT table to make it work. See DSDT.
Suspend/hibernate does not work, or does not work consistently
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.
Also problem may arise when using hardware watchdog timer (disabled by default, see RuntimeWatchdogSec= in systemd-system.conf(5) § OPTIONS). Bugged watchdog timer may reset the computer before the system finished creating the hibernation image.
Sometimes the screen goes black due to device initialization from within the initramfs. Removing any modules you might have in Mkinitcpio#MODULES and rebuilding the initramfs, can possibly solve this issue, specially graphics drivers for early KMS. Initializing such devices before resuming can cause inconsistencies that prevents the system resuming from hibernation. This does not affect resuming from RAM. Also, check the blog article best practices to debug suspend issues.
Moving from the radeon video driver to the newer AMDGPU driver could also help to make the hibernation and awakening process successful.
For Intel graphics drivers, enabling early KMS may help to solve the blank screen issue. Refer to Kernel mode setting#Early KMS start for details.
After upgrading to kernel 4.15.3, resume may fail with a static (non-blinking) cursor on a black screen. Blacklisting the module nvidiafb might help. [5]
Laptops with Intel CPU that load intel_lpss_pci module for touchpad, may face kernel panic on resume (blinking caps lock) [6]. The module needs to be added to initramfs as:
/etc/mkinitcpio.conf
MODULES=(... intel_lpss_pci ...)
Then regenerate the initramfs.
Wake-on-LAN
If Wake-on-LAN is active, the network interface card will consume power even if the computer is hibernated.
Instantaneous wakeups from suspend
See Wakeup triggers#Instantaneous wakeups from suspend.
System does not power off when hibernating
When you hibernate your system, the system should power off (after saving the state on the disk). Sometimes, you might see the power LED is still glowing. If that happens, it might be instructive to set the HibernateMode to shutdown in sleep.conf.d(5):
/etc/systemd/sleep.conf.d/hibernatemode.conf
[Sleep] HibernateMode=shutdown
With the above configuration, if everything else is set up correctly, on invocation of a systemctl hibernate the machine will shutdown saving state to disk as it does so.