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- Uswsusp
- systemd
- Power management
- Wakeup triggers
- swap

There are multiple methods of suspending available, notably:

Suspend to idle
  Called S0ix by Intel, Modern Standby (previously "Connected Standby") by Microsoft and S2Idle by the kernel. Designed to be used instead of the S3 sleeping state for supported systems, by providing identical energy savings but a drastically reduced wake-up time.
  Tip: While this state is subject to battery drain issues on Windows or macOS since they support waking devices in this state for network activity, the Linux software ecosystem does not currently make use of this feature and should be unaffected.
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.
Hybrid suspend (aka hybrid sleep)
  A hybrid of suspending and hibernating, sometimes called suspend to both. Saves the machine's state into swap space, but does not power off the machine. Instead, it invokes the default suspend. Therefore, if the battery is not depleted, the system can resume instantly. 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 the 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.

### Userspace (uswsusp)

The uswsusp ('Userspace Software Suspend') tools provide wrappers around the kernel's suspend-to-RAM mechanism, which perform some graphics adapter manipulations from userspace before suspending and after resuming. See main article Uswsusp.

## High level interfaces

The 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 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).

## Changing suspend method

On systems where S0ix suspension does not provide the same energy savings as the regular S3 sleep, or when conserving energy is preferred to a quick resume time, changing the default suspend method is possible.

Tip: S0ix is supposed to provide identical or better energy savings as S3 sleep. See Intel blog posts How to achieve S0ix states in Linux, Linux S0ix Troubleshooting and Idling Efficiently on Linux: A Case Study to check if you can make it work as intended.

Run the following command to see all suspend methods hardware advertises support for (current method is shown in square brackets[1]):

    $ cat /sys/power/mem_sleep

    [s2idle] shallow deep

If your hardware does not advertise the `deep` sleep status, check first if your UEFI advertises some settings for it, generally under Power or Sleep state or similar wording, with options named Windows 10, Windows and Linux or S3/Modern standby support for S0ix, and Legacy, Linux, Linux S3 or S3 enabled for S3 sleep. Failing that, you can keep using `s2idle`, consider using hibernation or try to patch the DSDT tables (or find a patched version online).

Note: This last solution is likely going to cause issues. Manufacturers have stopped fixing bugs with the ACPI S3 state since systems shipping with Windows are encouraged to use "Modern standby" by default; if they have voluntarily not advertised it, it is probably broken in some way.

Confirm that your hardware does not exhibit issues with S3 sleep by testing a few sleep cycles after changing the sleep method:

    # echo "deep" > /sys/power/mem_sleep

If no issues have been found, you can make the change permanent with the `mem_sleep_default=deep` kernel parameter.

In some opposite situations, faulty firmware advertises support for `deep` sleep, while only `s2idle` is supported. In this case, an alternative method for using `s2idle` is available through the `SuspendState` in sleep.conf.d(5):

    /etc/systemd/sleep.conf.d/freeze.conf

    [Sleep]
    SuspendState=freeze

## Hibernation

In order to use hibernation, you must create a swap partition or file, and 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 so that the kernel will attempt to resume from the specified swap in early userspace. These three steps are described in detail below.

Note:

- See Dm-crypt/Swap encryption#With suspend-to-disk support when using encryption.
- linux-hardened does not support hibernation, see FS#63648.
- Hibernating to swap on zram is not supported, even when zram is configured with a backing device on permanent storage. logind will protect against trying to hibernate to a swap space on zram.

### About swap partition/file size

Even if your swap partition is smaller than RAM, you still have a good 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. systemd#systemd-tmpfiles - temporary files can be used to make this change persistent:

    /etc/tmpfiles.d/hibernation_image_size.conf

    #    Path                   Mode UID  GID  Age Argument
    w    /sys/power/image_size  -    -    -    -   0

The suspend image cannot span multiple swap partitions and/or swap files. It must fully fit in one swap partition or one swap file.[2]

### Configure the initramfs

- When an initramfs with the `base` hook is used, which is the default, the `resume` 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 the `resume` hook must go after the `udev` hook. This example was made starting from the default hook configuration:

      HOOKS=(base udev autodetect modconf kms keyboard keymap consolefont block filesystems resume fsck)

  Remember to regenerate the initramfs for these changes to take effect.

  Note: LVM users should add the `resume` hook after `lvm2`.

- When an initramfs with the `systemd` hook is used, a resume mechanism is already provided, and no further hooks need to be added.

### 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-f495-4c43-8a03-5363dd433153`
- `resume="PARTLABEL=Swap partition"`
- `resume=/dev/archVolumeGroup/archLogicalVolume` -- if swap is on a LVM logical volume (UUID and Label should also work)

The kernel parameters will only take effect after rebooting. 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`. [3]

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=UUID=swap_device_uuid` 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.

On file systems other than Btrfs, 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 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 and the kernel parameter would be `resume_offset=38912`.

For Btrfs, do not try to use the filefrag tool, since 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.[4] Instead, use the btrfs-inspect-internal(8) command. E.g.:

    # btrfs inspect-internal map-swapfile -r /swap/swapfile

    198122980

In this example, `swap_file_offset` is `198122980` and the kernel parameter would be `resume_offset=198122980`

Tip:

- The following command may be used to identify `swap_device_uuid`: `findmnt -no UUID -T /swapfile`
- The following command may be used to identify `swap_file_offset` on file systems other than Btrfs: `filefrag -v /swapfile | awk '$1=="0:" {print substr($4, 1, length($4)-2)}'`
- The value of `swap_file_offset` can also be obtained by running `swap-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.conf` via the keys `resume device` and `resume offset`. No reboot is required in this case.

Note:

- For a stacked block device such as an encrypted container (LUKS), RAID or LVM, the `resume` parameter 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.

Tip: You might want to decrease the swappiness for your swap file if the only purpose is to be able to hibernate, not to expand RAM.

#### 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.

Warning: Do not to use TRIM on thinly-provisioned swap volumes that are used for hibernation, i.e. do not use `discard` in `/etc/fstab` and the `-d`/`--discard` option of swapon. Otherwise the used space will be deallocated.

## Intel Rapid Start Technology (IRST)

Intel Rapid Start Technology is a firmware method of hibernation that allows hibernating from sleep after a predefined interval or according to battery state. This should be faster and more reliable than regular hibernation as it is done by firmware instead of at the operating system level. Generally it must enabled in the firmware, and the firmware also provides support for setting the duration after suspend/battery event triggering hibernation. However, some devices–despite supporting IRST in the firmware–only allow it to be configured via Intel's Windows drivers. In such cases the intel-rst kernel module described below should be able to configure the events under Linux.

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 have a pre-existing IRST partition which can be retained during the Arch Linux installation process (rather than wiping and re-partitioning the whole SSD). It should show up as an unformatted partition equal in size to the system's RAM.

Warning: The Intel Rapid Start partition is not encrypted; "Intel recommends disabling Intel Rapid Start Technology if you are using software-based disk encryption".[5]

If you intend to wipe and re-partition 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.

Tip: The duration of time before IRST kicks in (after suspending) can be adjusted in the system's firmware settings.

The duration of the IRST hibernation process (i.e., copying the "entire contents of RAM to a special partition") is dependent 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.

Configuring IRST hibernation events in the Linux kernel requires `CONFIG_INTEL_RST` built-in or as a module. Once loaded via `modprobe intel_rst`, it should create the files `wakeup_events` and `wakeup_time` under `/sys/bus/acpi/drivers/intel_rapid_start/*/` that can be used for further configuration. This module is tersely documented, see the source drivers/platform/x86/intel/rst.c for more details.

See also the general Q&A and user guides[dead link 2023-07-30 ⓘ] 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.

A problem may arise when using the hardware watchdog timer (disabled by default, see `RuntimeWatchdogSec=` in systemd-system.conf(5) § OPTIONS). A buggy watchdog timer may reset the computer before the system finishes 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, removing the `kms` hook and rebuilding the initramfs can possibly solve this issue, in particular with 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 ATI video driver to the newer AMDGPU driver could also help to make the hibernation and awakening process successful.

For NVIDIA users, blacklisting the module `nvidiafb` might help. [6]

Laptops with an Intel CPU that load the `intel_lpss_pci` module for a touchpad may face kernel panic on resume (blinking caps lock) [7]. 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.

If you are using Linux kernel 6.1 and above on an AMD CPU, this can also be caused by an S3-related control policy issue in the kernel. A temporary solution would be turning off wakeup on related i2c devices. You can find them by

    $ ls /sys/bus/i2c/devices/*/power/wakeup

And the format of the device name should be `i2c-ELAN0679:00` or `i2c-MSFT0001:00`. Then, test if the below command can enter suspend:

    # echo disabled > /sys/bus/i2c/devices/device_name/power/wakeup
    # systemctl suspend

If it works, you can persist this config by adding udev rules:

    /etc/udev/rules.d/99-avoid-i2c-wakeup.rules

    KERNEL=="device_name", SUBSYSTEM=="i2c", ATTR{power/wakeup}="disabled"

### 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 shut down, saving state to disk as it does so.

### Operating system not found (or wrong OS booting) when booting after hibernation

This can happen when the boot disk is an external disk, and seems to be caused by a BIOS/firmware limitation. The BIOS/firmware tries to boot from an internal disk, while hibernation was done from an OS on an external (or other) disk.

Set `HibernateMode=shutdown` as shown in #System does not power off when hibernating to solve the problem permanently. If you have already locked yourself out, you can try rebooting your system 4 times (wait for the error to appear each time), which on some BIOS'es forces a normal boot procedure.

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