Problems with ACPI suspend-to-ram

The following glitches may or may not occur in relation to suspending to RAM:

Troubles on suspend

Permissions: If your suspend is failing, and a # tail /var/log/acpid shows "Permission denied" errors, be sure that your new ACPI event and action scripts have the appropriate permissions.

Broken sysfs interface: You may experience problems when using # echo standby > /sys/power/state or # echo mem > /sys/power/state (machine goes to sleep and wakes up immediately). This can be avoided by using # echo -n 3 >/proc/acpi/sleep to get it to sleep. This can be also happen if hotplug daemon is still running.

MySQL daemon running: If you're running MySQL, sleep may also not work, so stop MySQL first, then sleep. Remember to restart MySQL when you wakeup.

LCD backlight remains on during sleep: When your system is equiped with a Radeon Mobility graphic controller your LCD backlight may not turn off automatically. Use radeontool to switch off your backlight prior suspend in your sleep action script.

High power drain during sleep: Also, you might want to take note of the Problem with high power drain in ACPI sleep.

Blank display on resume: When resuming from a suspend-to-ram the display might remain black or might only show the pre-suspend output (the system is still rebootable via ctrlaltdel). Look here for solutions.

Broken hardware support after resume

The serial port of the port replicator might not work after resume.
The parallel port might not work after resume. A possible fix is to unload and reload the parallel port drivers: # rmmod lp parport_pc parport; modprobe lp.
Problems with the CD-RW/DVD drive after wake up from ram have been experienced.
There is a known Problem regarding battery info after suspend to RAM. A small patch exists for kernels 2.6.14/2.6.15.
On X20 and X21 (and possibly other) models, the sleep LED is not reset properly on resume and will keep blinking. If you have the ibm-acpi kernel module loaded with the experimental=1 option, you can switch it off on resume by appending the following line to your suspend script:

echo 7 off > /proc/acpi/ibm/led

Crash on resume

When using older ATI proprietary drivers a crash on resume can be solved by using vbetool. An example suspend script can be found here. This is no longer necessary with recent revisions of the ATI proprietary driver.
A crash could also be caused by having apic support enabled in the kernel config. Try disabling it (in the "Processor type and features" section).
On machines with Savage chipsets, the savagefb framebuffer driver might crash the machine on resume. Make sure it is disabled in your kernel config and use the standard vesafb driver instead.
Due to the fact that Sonoma chipset based laptops (R52, T43, T43p, X41, X41 Tablet) utilize the SATA layer for disk access and SATA does not have power-management support yet Suspend to RAM does these machines on resume. See the according section on the Problems with SATA and Linux page.

Shutdown on resume: If your system immediately begins to shut down right after resume, make sure you don't have acpid running with the power button tied to shutdown. The system is simply sensing the power button event and shutting down.