[mythtv-users] Scheduled wakeup acpi-alarm vs nvram-wakeup

mike choy mike at acaciaclose.co.uk
Fri Dec 30 09:15:24 EST 2005

mike choy wrote:
> Hi Team
> I wonder if its time to revisit ACPI for doing scheduled wakeups. This 
> looks much more elegant to me,
> and seems to have made real progress in 2.6.14 kernels. This will off 
> course need a Mother board and BIOS that supports the Real Time Clock 
> alarm function
> but as this is exposed via the OS, then this looks much safer than 
> poking directly into NVRAM.
> ( most BIOS have alarms that go upto 1 month ahead, some older ones 
> also only have 1 day ahead)!
> I am using SUSE 10.0 but would be interested if other distros now have 
> good ACPI support
> Here is a quick link to the ACPI documentation from Novell, and the 
> acpi4linux home page
> http://www.novell.com/documentation/suse10/index.html?page=/documentation/suse10/adminguide/data/sec_pmanage_acpi.html 
> http://acpi.sourceforge.net/
> Here are the results for my system
> Read the RTC alarm clock
>> cat /proc/acpi
>> cat /proc/acpi/alarm
> 2005-12-00 10:11:33
> Now check we can write a value back into the BIOS
> Login as root
> #echo 2005-12-31 10:30:00 >/proc/acpi/alarm
> Now check it worked
> #cat /proc/acpi
> 2005-12-31 10:30:00
> #shutdown -h now
> Note you will NOT see this change the wake up time in the BIOS
> And wait for the system to spin up.
> Now going away to see how to integrate to Myth
> Mike C
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> mythtv-users at mythtv.org
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Heres update with Mythtv integration, seems to work, just waiting for it 
to wake up against various schedules now.
Now test MythTV setup
In Mythtv-setup ->Shutdown/Wakeup Options
Startup command                               : Leave blank
Block shutdown before client connected        : Checked
Idle timeout(secs)                            :10s  (while I am testing)
Max wait for recordings(min)                  :15 mins (while I am testing)
Startup before rec(secs):                     :120
Wakeup time format                            :yyyy-MM-dd:hh:mm:ss
setwakeuptime command                         :sudo /usr/bin/mythsettime $time ( dont forget to schedule a recording or $time will be blank)
Server halt command                           :sudo /usr/sbin/mythshutdown
Pre Shutdown check-command:                   :exit 0

Now create (as Root) the mythsettime and mythshutdown scripts in /usr/sbin

mythsettime (chmod this to 755)
sudo echo $1 > /home/mythtv/myth.time
sudo echo $1 > /proc/acpi/alarm

mythshutdown (chmod this to 755)
sudo /sbin/halt -p

Add the following to the /etc/sudoers file (this gives permissions for above to run as root)
mythtv All=(ALL) NOPASSWD: /bin/echo,/sbin/halt,/usr/sbin/mythsettime,/usr/sbin/mythsettime

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