UbuntuHelp:PowerManagement/Hiberate

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https://help.ubuntu.com/community/PowerManagement/Hiberate

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Introduction

When a computer hibernates, it will save its current state to the hard disk and power down completely. When next the computer boots, the prior state is restored just as you left it. There are three methods of hibernation:

• kernel (aka suspend or swsusp): The linux kernel includes built-in support for hibernation. This method is triggered by modifying /sys/power/state.
• uswsusp: uswsusp is a rewrite of swsusp that does not rely on the kernel. Thus, uswsusp is a "userspace" tool because it is run entirely as a program separate from the kernel. It can be used by installing the package uswsusp and running sudo s2disk. This is reported to work in many situations where swsusp does not. Now supports encryption and compression for hibernation.
• !TuxOnIce (formerly suspend2): TuxOnIce has more features and works with more hardware than the other two. Unfortunately, it requires building and patching kernel your own kernel.

Here is a great comparison table of the various hibernation methods. The general impression is that swsusp was first, so is in the main kernel trunk, uswsusp is cool because it is userspace, while TuxOnIce is better but can't get in the kernel. There is a feud between the authors. Although is seems most users greatly prefer TuxOnIce when they try it out ('it just works'), it may never make it into the kernel.

swsusp

In Ubuntu, the default method of hibernation is to use swsusp which is built into the kernel. Gnome and pm-utils will use this method unless configured otherwise. The way you manually trigger hibernation using this 'kernel' method is to write 'disk' to /sys/power/state. There are two modes of 'kernel' hibernation: platform and shutdown. If one does not work, you can try the other:

sudo -s
echo platform > /sys/power/disk
echo disk > /sys/power/state

Or:

sudo -s
echo shutdown > /sys/power/disk
echo disk > /sys/power/state

Platform is the default and recommended mode of hibernation. Unfortunately, the "platform" mode of hibernation does not work on some systems with broken BIOSes. In such cases the "shutdown" mode of hibernation might work.

See Also

• Kernel notes on debugging hibernation

uswsusp

The package uswsusp (for Userspace Software Suspend) includes an executable called s2disk. This program is an alternate method of hibernation. In general, s2disk should not be called directly, but it can useful to do so for testing. Typically, the program pm-hibernate is responsible for calling s2disk. The s2disk program does the following in order to hibernate the machine:

1. Tell the kernel to create a snapshot of the current system state.
2. Read the snapshot data from the kernel and write it to the swap partition, possibly encrypting and compressing the data.
3. Power off the machine.

When next you power up, the reverse happens:

1. After a basic system boot, but before mounting any partitions, resume runs from the initrd.
2. The snapshot data from the swap partition is read (and possibly decrypted and decompressed).
3. resume tells the kernel to restore the snapshot.
4. the kernel returns at the place it was before the hibernation.

To install s2disk:

sudo aptitude install uswsusp

It is not generally useful to trigger s2disk manually, unless you are debugging. For example:

sudo tail -f /var/log/pm-suspend.log &
sudo s2disk

When you run s2disk manually like this, it is likely that when you restore a lot of your devices will not be working. To change your uswsusp settings:

sudo dpkg-reconfigure uswsusp

Alternately, you can edit /etc/uswsusp.conf manually.

Integrating uswsusp with pm-utils

Currently, installing s2disk does not actually make it so that it is used by gnome or pm-utils. To do so, edit /etc/pm/config.d/00sleep_module and change the value of SLEEP_MODULE:

SLEEP_MODULE="uswsusp"

Then, to test, you can run this:

sudo tail -f /var/log/pm-suspend.log &
sudo pm-hibernate

pm-hibernate (part of pm-utils) is the preferred way to run s2disk. By default, when you choose hibernate from within gnome, the command pm-hibernate will get called.

Troubleshooting

• I have encryption configured and when I resume the wrong term is open. To get to the password prompt, I have to hit Alt-1.

See Also

• OpenSUSE s2disk page

TuxOnIce

See Also

• Suspend2Kernel - building a kernel in ubuntu that supported !TuxOnIce
• Ubuntu Brainstorm: TuxOnIce for Ubuntu
• How to install TuxOnIce for Ubuntu