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This article is being considered for archiving.

Reason: µswsusp development is discontinued and the project was not updated since 2011. Most of what µswsusp did is now directly handled into the kernel. (Discuss in Talk:Uswsusp)

µswsusp (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.

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 functionalities of s2ram and s2disk and it is 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.


Install uswsusp-gitAUR.


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 by-label/swap must be replaced with the correct block device containing the swap partition.
  • If using a swap file:
    resume device = /dev/sdXN  # the partition which contains swapfile
    resume offset = 123456
    where X and N are the device letter and partition number, respectively, and 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 is 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 set to shutdown the machine will simply be powered down, which may cause trouble for some hardware.
  • 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, but they are not available in Arch Linux.
    Note: This requires additional configure flags for µswsusp (--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

Support for encryption

This article or section is out of date.

Reason: suspend-keygen is no longer available. See [1] (Discuss in Talk:Uswsusp)
  • generate a key with the suspend-keygen utility included in the package;
  • write the name of the key in /etc/suspend.conf;
encrypt = y
RSA key file = path_to_keyfile

Recreate initramfs

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.

Edit your /etc/mkinitcpio.conf file and add uresume to the HOOKS array.

HOOKS=(base udev autodetect block uresume filesystems)

and rebuild the ramdisk.

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.

Now you could try to suspend directly calling s2disk from the command line:

# s2disk

It is probably necessary to resort to a userspace tool which calls internally s2disk.

With systemd

To put your system into hibernation a.k.a Suspend to Disk with systemctl hibernate, edit systemd-hibernate.service, adding:

ExecStartPre=-/usr/bin/run-parts -v -a pre /usr/lib/systemd/system-sleep
ExecStartPost=-/usr/bin/run-parts -v --reverse -a post /usr/lib/systemd/system-sleep

After that, execute systemctl hibernate to put your system into hibernation. Make similar changes to systemd-hybrid-sleep.service (replace s2disk with s2both) to enable µswsusp-based hybrid sleep.


My machine is not whitelisted

If s2ram does not match your machine to an entry in its whitelist, it will output some general purpose identification strings for your machine (the same as those provided s2ram -i). In this case, you may try to force s2ram to suspend your machine by using s2ram -f.

s2ram -f does not work

If s2ram -f does not work, try the different workarounds offered by s2ram. Run s2ram -h to get a list of the possible options:

# s2ram -h
Usage: s2ram [-nhi] [-fspmrav]

    -h, --help:       this text.
    -n, --test:       test if the machine is in the database.
                      returns 0 if known and supported
    -i, --identify:   prints a string that identifies the machine.
    -f, --force:      force suspending, even on unknown machines.

The following options are only available with -f/--force:
    -s, --vbe_save:   save VBE state before suspending and restore after resume.
    -p, --vbe_post:   VBE POST the graphics card after resume
    -m, --vbe_mode:   get VBE mode before suspend and set it after resume
    -r, --radeontool: turn off the backlight on radeons before suspending.
    -a, --acpi_sleep: set the acpi_sleep parameter before suspend
                      1=s3_bios, 2=s3_mode, 3=both
    -v, --pci_save:   save the PCI config space for the VGA card.

Try the following variations:

# s2ram -f -a 1
# s2ram -f -a 2
# s2ram -f -a 3
# s2ram -f -p -m
# s2ram -f -p -s
# s2ram -f -m
# s2ram -f -s
# s2ram -f -p
# s2ram -f -a 1 -m
# s2ram -f -a 1 -s

If none of those combinations work, start again but add the -v switch.

Note that mixing the -a options and vbetool's options (-p, -m, -s) is normally only a measure of last resort, it usually does not make much sense.

If you find several combinations that work (e.g. s2ram -f -a 3 and s2ram -f -p -m both work on your machine), the in-kernel method (-a) should be preferred over the userspace methods (-p, -m, -s).

Verify all combinations in both cases when reporting success to the s2ram developers:

  • when issuing s2ram from console
  • when issuing s2ram from X

s2ram does not work with any combination of options

There is a trick which does not correspond to a command-line option, because it requires additional operations from you. It is marked with NOFB in the whitelist and used for those laptops which suspend and resume properly only if no framebuffer is used. If you verify that no command line option of s2ram works, you can try disabling the framebuffer. To do this, you need to edit your bootloader configuration, remove any possible vga=value values from the kernel line and reboot. This at least if you use the VESAFB framebuffer (as in the Arch default kernel). If you use a different framebuffer driver, refer to the documentation of the driver to see how to disable it.

See also

  • µswsusp home page
  • HOWTO file included with the Linux kernel source code
  • /usr/share/doc/suspend/README µswsusp documentation
  • /usr/share/doc/suspend/README.s2ram-whitelist s2ram-whitelist README