Difference between revisions of "Watchdog"

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(How to disable Watchdog: typo)
(How to disable Watchdog)
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Symlinking <tt>/sbin/shutdown</tt> to <tt>/usr/bin/true</tt> makes the shutdown command do nothing.
 
Symlinking <tt>/sbin/shutdown</tt> to <tt>/usr/bin/true</tt> makes the shutdown command do nothing.
  
There's also /usr/sbin/recovery_reboot shell script, which seems to tell OS X to reboot using recovery partition (only this time).  
+
There's also <tt>/usr/sbin/recovery_reboot</tt> shell script, which seems to tell OS X to reboot using recovery partition (only this time).  
Perhaps (pretty doubtful) it is called when watchdog sniffs something bad. Easiest way to check would that would be just adding something like "echo 'oh no, I am being recovery_rebooted' > /blah" and then see if /blah exists after your ATV was rebooted by a watchdog.
+
Perhaps (pretty doubtful) it is called when watchdog sniffs something bad. Easiest way to check would that would be just adding something like:
 +
<pre>
 +
echo 'oh no, I am being recovery_rebooted' > /blah
 +
</pre>
 +
and then see if <tt>/blah</tt> exists after your ATV was rebooted by a watchdog.
  
 
===Background information===
 
===Background information===

Revision as of 21:56, 24 March 2007

What is Watchdog

Watchdog reboots the Apple TV it if the GUI isn't running. There's a kext called AppleTCOWatchdog.kext in the /System/Library/Extensions/ folder.

How to disable Watchdog

Yet another failed attempt:

Auto restart is for automatically rebooting after a power failure and is present also on Mac. You can turn it off using: pmset autorestart 0
As you can see with pmset -g:

System-wide power settings:
SleepDisabled          1
Active Profiles:
AC Power                -1*
Currently in use:
 disksleep      0 
 hibernatemode  0
 displaysleep   0
 powerbutton    0
 sleep          0
 autorestart    0
 hibernatefile  /var/vm/sleepimage

Apparently BackRow.framework tells Watchdog that "we are up and running":

strings /System/Library/PrivateFrameworks/BackRow.framework/Versions/A/BackRow
(...)
BRSettingsHelper tellWatchdogWeAreUpAndRunning

Here is the code needed to call BackRow functions. Note you must add the BackRow framework to your project.

//BRSettingsHelper.h
#import <Cocoa/Cocoa.h>


@interface BRSettingsHelper : NSObject {

}

- (void) tellWatchdogWeAreUpAndRunning;  //This function seems to reset the boot count but does not prevent the machine from rebooting.
- (void) reboot;

@end

And now to test it:

#import <Cocoa/Cocoa.h>
#include "BRSettingsHelper.h"

int main(int argc, char *argv[])
{
    BRSettingsHelper * test = [[BRSettingsHelper alloc] init];

        [test reboot]; 
    
   
    return NSApplicationMain(argc,  (const char **) argv);
    
}

Note that to get this to work, the app had to be run as root.
There is also the key:
_kRUIAutoRestartIntervalKey

which is probably used in one of:

-[RUIPreferences boolForKey:]
-[RUIPreferences boolForKey:withValueForMissingPrefs:]
-[RUIPreferences canSetPreferencesForKey:]
-[RUIPreferences descriptionForKey:]
-[RUIPreferences floatForKey:]
-[RUIPreferences integerForKey:]
-[RUIPreferences objectForKey:]
-[RUIPreferences setBool:forKey:]
-[RUIPreferences setFloat:forKey:]
-[RUIPreferences setInteger:forKey:]
-[RUIPreferences setObject:forKey:]
-[RUIPreferences stringForKey:]

This seems to indicate that the auto reboot interval is stored as a key somewhere. I don't know if this is simply used for the Finder.app or if there is something else on the system that will use this.


SettingsHelper has a reference to /sbin/shutdown -r now

Symlinking /sbin/shutdown to /usr/bin/true makes the shutdown command do nothing.

There's also /usr/sbin/recovery_reboot shell script, which seems to tell OS X to reboot using recovery partition (only this time). Perhaps (pretty doubtful) it is called when watchdog sniffs something bad. Easiest way to check would that would be just adding something like:

echo 'oh no, I am being recovery_rebooted' > /blah

and then see if /blah exists after your ATV was rebooted by a watchdog.

Background information

This Apple document about Watchdog may shed some light:

http://docs.info.apple.com/article.html?artnum=106588&coll=cp (However, on the Apple TV, there is no /etc/watchdog.conf, other than what this document is saying)

Watchdog is not used in Mac OS X 10.4: look at launchd. This is referring to a software watchdog and is probably unrelated to the rebooting problem.