Power management/Suspend and hibernate
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Manually suspending the operating system, either to memory (standby) or to disk (hibernate) sometimes provides the most efficient way to optimize battery life, depending on the usage pattern of the laptop. While there is relatively straightforward support in the linux kernel to support these operations, typically some adjustments have to be made before initiating these operations (typically due to problematic drivers, modules or hardware). The following tools provide wrappers around the kernel interfaces to suspend/resume
- Wrappers: Systemd, pm-utils
- Backend: kernel, uswsusp, tuxonice
Suspension works out-of-box.
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_sizecontrols 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. As
<swap_partition> you can use either kernel name of the swap partition, i.e.
/dev/sda1, or the UUID of the swap partition. See Kernel parameters for more examples for various bootloaders.
For example, with GRUB2 you can use
And if you use UUID instead:
Don't forget to run
grub-mkconfig -o /boot/grub/grub.cfg afterwards.
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
ilesystem 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
Recreate initial ramdisk
If you use an initramfs (default Arch systems do), you must add the
resume hook into the HOOKS in the configuration of mkinitcpio:
# resume must be placed after block and lvm2, but before filesystems HOOKS="... block lvm2 resume filesystems ..."
Finally, you must rebuild the initrd image for these changes to take effect:
# mkinitcpio -p linux
uswsusp (userspace software suspend) is a set of user space tools used for hibernation (suspend-to-disk) and suspend (suspend-to-RAM or standby) on Linux systems.
TuxOnIce , an advanced suspend/hibernate framework which supports suspending to a swap-disk or a regular file with fast LZO-compression.
$ systemctl suspend $ systemctl hibernate $ systemctl hybrid-sleep
# pm-suspend # pm-hibernate # pm-suspend-hybrid