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Software Suspend 2 - swsusp2

Software Suspend 2, sometimes also called "swsusp2" and "suspend2", is an implementation of suspend-to-disk functionality in the form of a Linux kernel patch and several userspace utilities. It is an alternative to both the BIOS-driven hibernation feature found on most ThinkPad models, and the swsusp "software suspend" functionality built into recent Linux kernels.


Compared to the alternatives, Software Suspend 2 has some unique features:

  • Saving the memory image into a swap file, a swap partition or a normal file on any filesystem.
  • Cancelling a suspend in progress.
  • Different bugs -- if the alternatives don't work, try this one!

It also have the following advantages over swsusp (these features are also provided, in principle, by the not-yet-stable uswsusp):

  • The ability to compress the memory image as it is written to disk, thereby reducing suspend and resume times.
  • Control over amount of RAM written to disk -- can (optionally) discard cached disk blocks to reduce suspend and resume times.
  • Textual and graphical UI (optional).

Since it is implemented purely in software, Software Suspend 2 is in principle machine-independent and should work on all modern ThinkPad models. However, in some cases problematic drivers need to be unloaded before suspension. This is handled by the hibernate script (see below).

Availability / Project Homepage

Model-specific Status

Thinkpad Model Type Operating System Kernel Version Suspend2 Version Success Note
240 2609-21G Zenwalk 4.2 2.2.9 Yes
T60p 2.2.9 Yes Requires "ProcSetting extra_pages_allowance 7500" in hibernate.conf, SATA mode set to compatibility in BIOS and the DMA fix from Problems with SATA and Linux
T60 2007-77G Yes Requires "ProcSetting extra_pages_allowance 7500" in hibernate.conf
T42 Yes
T43 Yes
T21 Yes need to unload the sound module (snd-cs46xx) on suspend. May want to enable UseDummyXServer if running X
T21 2647-4BG Ubuntu 6.10 Edgy Eft Yes I used experimental Trevino's kernel packages
X41 Tablet Fedore Core 4 Yes requires SATA resume patch and the SATA drivers compiled as built-in or in initrd (see Problems with SATA and Linux) and a hibernate.conf fix (see Installing Fedora Core 4 on a ThinkPad X41 Tablet)
X22 Ubuntu Breezy Yes see Installing Ubuntu (Breezy) on a ThinkPad X22
G41 Yes see Installing Debian on a ThinkPad G41
R51 1829 Yes
R51e 2.6.16-suspend2-r8 Yes Requires "ProcSetting extra_pages_allowance 8000" in hibernate.conf
R52 2.2.7 Yes FC5 with kernel 2.6.17-1.2145_1.rhfc5.cubbi_suspend2
T23 2647-9KU Debian Etch 2.2.7 Yes
X60s 1702-55G Arch Linux 2.2.8 Yes I use the beyond patchset
Z61m 9452-CTO Kubuntu Edgy 2.2.9 from experimental repository from http://3v1n0.tuxfamily.org/dists/edgy/suspend2/ Yes I have blacklisted these modules: tg3, tp_smapi, hdaps, uhci_hcd (fingerprintreader would not go into suspend), sdhci. More options in the hibernate scripts are "IbmAcpi" and "ProcSetting extra_pages_allowance 15000". SATA mode set to compatibility in BIOS

Installation Instructions

The project home page has a detailed HOWTO and FAQ. The following are just a few highlights.

Modifying the initrd generation scripts, and recreate initrd

If your systems uses an initrd file (most do), you'll need to patch or replace your initrd-creation script.

  • Fedora 4: in /sbin/mkinitrd, find this line:
echo "echo Mounted /proc filesystem" >> $RCFILE

and add the following immediately afterwards:

echo "echo > /sys/power/suspend2/do_resume" >>$RCFILE
  • Fedora 5: in /sbin/mkinitrd, find this line:
if [ -z "$noresume" -a -n "$swsuspdev" ]; then

and add the following immediately before the above:

emit "echo 1 > /sys/power/suspend2/do_resume"

You can also use the mkinitrd-suspend2 package from atrpms.

  • Debian: If your system uses mkinitrd to create the initrd, copy swsusp-initrd.sh script to your /etc/mkinitrd/scripts directory before creating initrd image. If you use initramfs-tools, put a similar script into /etc/initramfs-tools/scripts/local-top/ (the manpage of initramfs has templates of example "boot scripts")

In any case, make sure you regenerate your initrd file by reinstalling the kernel package or explicitly with mkinitrd or mkinitramfs commands.

Hibernate script

Software Suspend 2 works best with the hibernate script (available from the project home page), which takes care of auxiliary tasks needed on many systems (e.g., unloading problematic modules and restoring video modes).


Configuration tips

RediSafe-like functionality

The hibernate functionality on some ThinkPad BIOSes offers the useful "RediSafe" feature, which suspends to both RAM and disk. This way you get quick resumes (directly from RAM), plus the safey of suspend-to-disk in case the battery runs out.

Software Suspend 2 provides this feature too; simply add the following to /etc/hibernate/suspend2.conf:

PowerdownMethod 3

Be aware of possible filesystem corruption scenarios

Certain usage scenarios can cause filesystem corruption with suspend2. Some details on this are in the project's HOWTO. None of the workaround configurations fix the problem satisfactorily, so be warned. In particular, with an ext3 root filesystem, if you suspend to swap partition, and then use sysrescCD/Knoppix/some other way to mount the root filesystem read-only, you risk data corruption when you try to resume from the suspended image.

As far as possible, after suspending the system, don't touch the root filesystem unless you are resuming from it :)