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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. It consists of:

  • s2ram - a wrapper around the kernel's suspend-to-RAM mechanism allowing the user to perform some graphics adapter manipulations from the user land before suspending and after resuming that may help to bring the graphics (and the entire system) back to life after the resume. Incorporates the functionality of vbetool and radeontool as well as some tricks of its own. Includes a list of working hardware configurations along with the appropriate sets of operations to be performed to resume them successfully. This is accomplished by a hardware whitelist maintained by HAL - s2ram translates the HAL database options into s2ram parameters.
Note: Since HAL is deprecated and KMS drivers can save the state of the grahic card directly without userspace quirks, s2ram development is discontinued and no further whitelist entries are accepted. If a KMS driver is in use, s2ram will directly suspend the machine.
  • s2disk - the reference implementation of the userspace software suspend (µswsusp); it coordinates the steps necessary to suspend the system (such as freezing the processes, preparing the swap space, etc.) and handles image writing and reading. s2disk already supports compression and encryption of the image and other features (e.g. a nice progress bar, saving the image on a remote disk, playing tetris while resuming, etc.) can be easily added.
  • s2both - combines the funtionalities of s2ram and s2disk and it's very useful when the battery is almost depleted. s2both writes the system snapshot to the swap (just like s2disk) but then puts the machine into STR (just like s2ram). If the battery has enough power left you can quickly resume from STR, otherwise you can still resume from disk without losing your work.


uswsusp is available in the AUR under the name uswsusp-git.


You must edit /etc/suspend.conf before attempting to suspend to disk.

  • If using a swap partition:
resume device = /dev/disk/by-label/swap

where /dev/disk/by-label/swap must be replaced with the correct block device containing the swap partition.

resume device = /dev/sdX  # the partition which contains swapfile 
resume offset = 123456

where 123456 is the offset from the beginning of the resume device where the swap file's header is located. The resume offset can be obtained by running

# swap-offset your-swap-file
  • The image size parameter (optional) can be used to limit the size of the system snapshot image created by s2disk. If it's not possible to create an image of the desired size, s2disk will suspend anyway, using a bigger image. If image size is set to 0, the image will be as small as possible.
  • The shutdown method parameter (optional) specifies the operation that will be carried out when the machine is ready to be powered off. If set to "reboot" the machine will be rebooted immediately. If set to "platform" the machine will be shut down using special power management operations available from the kernel that may be necessary for the hardware to be properly reinitialized after the resume, and may cause the system to resume faster.
  • If the compute checksum parameter is set to 'y', the s2disk and resume tools will use the MD5 algorithm to verify the image integrity.
  • If the compress parameter is set to 'y', the s2disk and resume tools will use the LZF compression algorithm to compress/decompress the image.
  • If splash is set to 'y', s2disk and/or resume will use a splash system. Currently splashy and fbsplash are supported.
    Note: This requires additional configure flags for uswsusp (--enable-splashy and --enable-fbsplash, respectively).
  • The resume pause option will introduce a delay after successfully resuming from hibernation, in order to allow the user to read the stats (read and write speed, image size, etc.)
  • If threads is enabled, s2disk will use several threads for compressing, encrypting and writing the image. This is supposed to speed things up. For details, read the comments in suspend.c

Now you need to recreate an initramfs with the new hook. Edit your /etc/mkinitcpio.conf file and add "uresume" to the HOOKS entry.

HOOKS="base udev autodetect pata scsi sata uresume filesystems"
  • rebuild the ramdisk
# mkinitcpio -p linux

See for further informations.

Note: Whenever you modify /etc/suspend.conf, you will need to rebuild your initramfs. If you fail to do so, and linux cannot find your image at startup, you will not see an error message indicating this. Your boot process will hang after starting the uresume hook, typically after the message with the libgcrypt version.

Sample config

snapshot device = /dev/snapshot

resume device = /dev/disk/by-label/swap

# image size is in bytes
image size = 1468006400

#suspend loglevel = 2

compute checksum = y

compress = y

#encrypt = y

#early writeout = y

#splash = y

# up to 60 (seconds)
#resume pause = 30  

threads = y



To suspend to disk, run:

# s2disk

To suspend to ram, first run:

# s2ram --test

to see if your machine is in the database of machines known to work. If it returns something like "Machine matched entry xyz" then go ahead and run:

# s2ram

Otherwise, the --force parameter will be necessary, possibly combined with other parameters (see s2ram --help). It may fail.

With pm-utils

Pm-utils can utilise several sleep back-ends, including uswsusp. Create or edit /etc/pm/config.d/module:


This way, pm-suspend and pm-hibernate will use uswsusp. There is an advantage to this: regular users can use these commands to suspend with uswsusp:

$ dbus-send --system --print-reply --dest="org.freedesktop.UPower" /org/freedesktop/UPower org.freedesktop.UPower.Suspend

$ dbus-send --system --print-reply --dest="org.freedesktop.UPower" /org/freedesktop/UPower org.freedesktop.UPower.Hibernate
Note: The user's window manager or desktop environment needs to be started either with a login manager like gdm or kdm, or with exec ck-launch-session <window-manager>. Also, upower needs to be installed.

With systemd

To to put your system into hibernation a.k.a Suspend to Disk with systemctl hibernate, do:

# cp /usr/lib/systemd/system/systemd-hibernate.service /etc/systemd/system/
# cd /etc/systemd/system/

Open systemd-hibernate.service with your preferred text editor and edit the line from this:

ExecStart=/usr/lib/systemd/systemd-sleep hibernate

to this:


After that, execute systemctl hibernate to put your system into hibernation.

Further reading

Most of this page is adapted/copied from the HOWTO file included with the source code.
The introduction is from