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21. March 2013

Linux: ACPI disabled, won’t shut down, /sys/class/rtc/rtc0/wakealarm vanished

Filed under: Linux — Tags: , , , , , , , , , , , — Christopher Kramer @ 00:16

MythTV server won’t shut down automatically any longer

Today my mythTV based media homeserver suddenly would not automatically shutdown any longer after a kernel update.

Logs by mythbackend (/var/log/mythtv/mythbackend ) that triggers the shutdown  looked like this:

localhost mythbackend[1674]: I Scheduler scheduler.cpp:2729 (CheckShutdownServer) CheckShutdownServer returned - OK to shutdown
localhost mythbackend[1674]: N Scheduler scheduler.cpp:2814 (ShutdownServer) Running the command to set the next scheduled wakeup time [...]
localhost mythbackend[1674]: E Scheduler scheduler.cpp:2820 (ShutdownServer) SetWakeuptimeCommand failed, shutdown aborted

Problem: /sys/class/rtc/rtc0/wakealarm vanished after kernel update

So I ran the SetWakeupTime command myself and go this problem:

/sys/class/rtc/rtc0/wakealarm: No such file or directory

And in fact the file was missing.

System won’t power off any longer

I tried to shut down the pc completely (manually) and start it again. But it wouldn’t power off, it just freezed with the shutdown bar on the screen. Pressing the power button once (only short, not holding it) made the PC power off.

So this looked like some big ACPI problem.

ACPI disabled

After some more search, I found this in the syslog (/var/log/syslog):

localhost kernel: [    0.000000] ACPI: no DMI BIOS year, acpi=force is required to enable ACPI
localhost kernel: [    0.000000] ACPI: Disabling ACPI support

So no ACPI support explains why wakealarm and shutdown is broken.

I am wondering why this happens suddenly after a kernel update (I have not changed my BIOS or something and ACPI was perfectly working before).

Solution: force ACPI

Forcing ACPI solved the problem.

If you use grub2, this is how to do it:

Open /etc/default/grub (e.g. “sudo nano /etc/default/grub”) and update this line:


Into this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force"

Save the file and update the grub configuration:

sudo update-grub

Then restart and you’ll be done.

sudo shutdown -r now

I hope this could help somebody.


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19. August 2012

MythTV: DVD playback does not work

Filed under: Linux — Tags: , , , , , , — Christopher Kramer @ 00:09

A colleague of mine who is currently setting up Mythbuntu (MythTV) as a media center PC contacted me today because he had a problem with DVD playback in MythTV. When selecting DVD-playback, just nothing happend.

I first asked him to make sure the DVD drive is working and the DVD can be mounted and he confirmed it works (you should check as well).

Then I asked him to launch MythTV from the console (e.g. in Gnome Terminal, run “mythfrontend”) and try to play the dvd and see whether an error message is logged in the terminal window. And in fact MythTV complained:

faild to open device at /dev/dvd

I asked him to send me the list of his devices using:

ls /dev

This showed up no device “dvd” (the dvbt-stick created a “dvb”-device, so not get confused with that). The dvd-device in fact had the name “dvd1”. So with this knowledge, the problem is easy to fix:

ln -s /dev/dvd1 /dev/dvd

So this creates a symbolic link so /dev/dvd1 can be accessed using /dev/dvd as well so MythTV is pleased.

Hope this helps some of you.