Does this only work on x86_64?
Works fine on X86_32 for me --Benjsc 12:56, 3 October 2006 (UTC)
It works on 32 bit as well. If you miss /proc/acpi/alarm then it seems that this dissapears if you run smp.
Does anyone have experience with the Via EPIA boards? I'm not able to get it working and thus still use nvram-wakeup...
How do I use ACPI wakeups with MythWelcome? The instructions for it are all for using it with nvram-wakeup. --Turpie 11:09, 29 December 2006 (UTC)
http://svn.mythtv.org/trac/ticket/2838 Looks like capability for ACPI with MythWelcome is coming. Hopefully we'll see an update to the WIKI once 0.21 comes out or sooner if someone with svn version gets ambitious.
I just updated my fedora 7 kernel and apparently the 2.6.22 linux kernel removes the /proc/acpi/alarm feature, see http://lkml.org/lkml/2007/6/22/320 does anyone know the new method for these new kernels? --Vossman 06:18, 23 July 2007 (UTC)
There is no documentation, only some hidden description in the git commit that introduced this feature. So I wrote some short documentation, but it isn't included in the source tree yet, AFAIK.
It can be found here:
There is also a message in the mythtv mailing list here:
I found a note here that says: "Also it seems, that /sys/class/rtc/rtc0/wakealarm only accepts times more than 2h in the future." If you are having problems this might be it.
--Vossman 07:25, 7 September 2007 (UTC)
I am having the same issue as this guy here  I have no trouble getting the value into the /sys/class/rtc/rtc0/wakealarm that is all fine and dandy. But my machine does not wake up when I set this value. I use Fedora 7 and /proc/acpi/alarm worked great before. I am thinking of reporting this to bugzilla.kernel.org and bugzilla.redhat.com if other people are experiencing this post a comment. --Vossman 16:01, 8 September 2007 (UTC)
Fedora Core 6 kernel 126.96.36.199 vs kernel 188.8.131.52
I have a backend running FC6 (kernel 184.108.40.206-49.fc6) that shuts down and wakes up just fine using the script mentioned in the article. However, after upgrading to kernel 220.127.116.11-61.fc6, it no longer works. I figured out (thanks to the comment in the article) that a new wakeup mechanism is in place for the new kernel, namely /sys/class/misc/rtc/power/wakeup. I tried using that, but all I get when I try to echo anything into it (as root) is "invalid argument". Even resetting fails (echo 0 > /sys/class/misc/rtc/power/wakeup). As of writing, this article is the *only* place that mentions this path in google's index. I've reverted to the 18.104.22.168 kernel which still works great, using mythtv-0.20.2-167.fc6. Judaz 19:16, 6 November 2007 (UTC)
This is in response to Judaz's post above. /sys/class/rtc/rtc0/wakealarm has NOT been moved to /sys/class/misc/rtc/power/wakeup. The documentation provided with the kernel source explains that the wakeup file is a way to query/set whether a device in the system can wakeup. Here's an excerpt from the 22.214.171.124 kernel source documentation that describes the power/wakeup files in sysfs (found in Documentation/power/devices.txt):
/sys/devices/.../power/wakeup files ----------------------------------- All devices in the driver model have two flags to control handling of wakeup events, which are hardware signals that can force the device and/or system out of a low power state. These are initialized by bus or device driver code using device_init_wakeup(dev,can_wakeup). The "can_wakeup" flag just records whether the device (and its driver) can physically support wakeup events. When that flag is clear, the sysfs "wakeup" file is empty, and device_may_wakeup() returns false. For devices that can issue wakeup events, a separate flag controls whether that device should try to use its wakeup mechanism. The initial value of device_may_wakeup() will be true, so that the device's "wakeup" file holds the value "enabled". Userspace can change that to "disabled" so that device_may_wakeup() returns false; or change it back to "enabled" (so that it returns true again).
The wakealarm file should still reside in /sys/class/rtc/rtcN. If that directory does not exist on your system, it means the kernel was compiled without support for /sys/class/rtc/rtcN. If you're building your own kernel, you can enable it in "make menuconfig" via the following:
Device Drivers -> Real Time Clock -> /sys/class/rtc/rtcN (sysfs)
If you're using prebuilt kernel packages and /sys/class/rtc doesn't exist, complain to your distro maintainer. Hope this saves someone else the headache it's put me through! --Ebenblues 22:19, 9 January 2008 (UTC)
strage stript for the wakealarm feature in new kernels
The script is somewhat strange in some parts.
#!/bin/sh # $1 is the --settime switch that nvram-wakeup normally expects # $2 is the date/time in seconds since 1970 DATE=`date -d "1970-01-01 $2 sec" "+%F %H:%M:%S" -u` SECS=`date -d "1970-01-01 $2 sec" "+%s" -u`
Why is the argument $2, which is seconds since epoch, converted into seconds since epoch? I think that part can be scratched. Just echo $2 > /sys/class/rtc/rtc0/wakealarm should do fine (at least it does for me)
# Save the wakeup time echo "$*" > /myth.wakeup.args echo $DATE > /myth.wakeup.time echo $SECS > /myth.wakeup.secs
Why are files written into the root directory? Just scratching the "> /myth.wakeup.args" should be fine, as the echo output can be seen in the backend log then.
I got this to work in 2.6.24
I'm running Fedora 8, 126.96.36.199-92, and this works. Note that I had to first use the FC6 fix located on this page.
If I run these commands, my pc will wake up in 5 minutes.
su chmod ugo+rwx /proc/acpi/alarm echo "+00-00-00 00:05:00" > /proc/acpi/alarm halt -p
Note that if I use shutdown -h now, or /etc/init.d/halt start, or something else, it DOES NOT work. Only halt -p!
Also, I did not have a /sys/class/rtc folder, but I did have a /proc/rtc file. No /proc/rtc0 either.
Rlbond86 23:14, 22 May 2008 (UTC)