Difference between revisions of "Suspend"

Revision as of 15:58, 24 February 2008

This article describes how to suspend your MD to RAM (standby) or to disk (hibernation).

Please note that this functionality is not yet integrated into LinuxMCE, and will thus need some editing of Linux configuration files. Integration of the suspend functions has been reported in the issue-tracking system, you might check the Mantis bug tracker for any progress.

Motivation

• Saving power
• Quick boot (usefull if your MD is noisy and you turn it off when not in use)

Setup

There are several different ways of achiving suspend, this is one using the hibernate scripts, which can be configured to use different ways of suspending the machine.

On the MD in question, make sure you have the uswsusp and hibernate packages installed.

apt-get install uswsusp hibernate

Check your BIOS setting to make sure that suspend to ram is enabled.

Using NVidia graphics card

Edit your xorg.conf file and add this line to the "Device" section:

Option "NvAGP" "1"

Also make sure no other vendor AGP modules are loaded, like intel_agp, sis_agp etc. The agpgart module is fine, though. Use

lspci | grep agp

to list all loaded agp modules.

If you see any agp modules besides agpgart, add a line to /etc/modprobe.d/blacklist to blacklist the module.

Edit the /etc/hibernate/ram.conf file, and comment the two lines

#EnableVbeTool yes
#VbetoolPost yes

Edit the /etc/hibernate/blacklisted-modules, and comment the line:

#nvidia

Enable wake on lan

To enable wake on lan, to let the core wake up the MD, you have to run a command to enable this before going to sleep. The normal shutdown process does this, but this is not run when suspending the computer. Hibernate provides a way of including our own scripts before suspending.

Add a file (i.e. enableWOL) to the /etc/hibernate/scriptlets.d/ folder:

AddSuspendHook 15 EnableWOL

EnableWOL() {
    ethtool -s eth0 wol g
}

Lirc module unloading and reloading

Some lirc modules (at least lirc_serial) needs reloading after suspend. Like for enabling wol, we add a file in the /etc/hibernate/scriptlets.d/ folder, with a descriptive name lirc.

# Stops and unloads the current lirc module before suspending, and
# restarts lirc when resuming

AddSuspendHook 30 UnloadLirc
AddResumeHook 30 StartLirc

UnloadLirc() {
    /etc/init.d/lirc stop
    if [ -f /etc/lirc/hardware.conf ];then
        . /etc/lirc/hardware.conf
        rmmod $MODULES
    fi
}

StartLirc() {
    /etc/init.d/lirc start
}

Suspend to RAM

Run

hibernate-ram

to suspends the MD to ram. The script first checks if it recognizes your hardware, to take the correct actions before suspending. If you get a message that your machine is unknown, edit the /etc/hibernate/ususpend-ram.conf file, and un-comment the

USuspendRamForce yes

line, to force it to suspend anyway.

Suspend to disk / Hibernation

Before trying to set up suspend to disk, I recommend that you first get suspend to ram working. All setup needed for suspend to RAM is also required for suspend to disk.

To enable suspend to disk, you will need to set up a swap partition on the MD in question. This is because the suspend implementation in the current kernel can only save the memory to the swap area. To achieve this on a diskless MD, you might use a CF card and a CF/IDE adapter. A CF card with 1 or 2 GB should be sufficient. However, with a CF card, you should make sure your MD has enough physical ram to avoid using swap, because CF cards may have lower performance than a normal IDE disk.

Edit the /etc/fstab file for the MD and add an entry for the swap partition

/dev/sda1 none            swap    sw              0       0

Adjust the partition to match your swap partition. Make sure you select the right one, or you WILL destroy your data. In the case of a diskless MD, you will probably only have one partition (a CF card for instance). You might need to do partitioning on the disk if it is a empty disk. This is outside the scope of this article.

Copy two files from /usr/share/initramfs-tools/scripts/local-premount/ (resume, uswsusp) into /etc/initramfs-tools/scripts/nfs-premount/ Not sure if both files are required, but it doesn't hurt.

These scripts will run before any file systems have been mounted, and after any disk drivers has been loaded. Both are important: mounting any file systems before resuming can corrupt your data, according to the documentation. And we need to have the drivers loaded to access the suspended image.

After copying the two files, run

update-initramfs -u

to update the initramfs image, which includes the scripts in the boot up process.

Now reboot your MD. When it has started up again, you can type

hibernate-disk

to initiate suspend to disk.

References

The hibernate script uses uswsusp by default when trying to suspend to ram. For more information about the s2ram utility used, read the S2ram howto

The NVidia suspend howto