System keeps waking from sleep every 2 hours

Same issue but in El Capitan. Looked this up, and RTC alarm is a common feature on PCs (https://en.wikipedia.org/wiki/Real-time_clock_alarm). I have cron and other background tasks that run periodically, so my guess is it's one of those. But I don't have time to hunt it down for now, so I'll disable wake-on-LAN and "start after power failure," and if that doesn't work, I'll just disable sleep and let it run.

Update: It sleeps properly with "start after power failure" and WoL disabled. Maybe it'll also work with just one of those disabled. Luckily, I don't need those features, but this does seem like a bug 😕

This seems to work on my Yosemite system:

sudo defaults write /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist ProgramArguments -array-add -DisableSleepProxyClient

Basically, this adds a <string>-DisableSleepProxyClient</string> as the last entry in the ProgramArguments.

You then Restart to make it take effect. This may affect the "Bonjour Sleep Proxy". I haven't tested it. What I do know is that my RTC (Alarm) has stopped.

Well, I can't seem to be able to Edit my previous post. The change I suggested works TOO WELL. It causes things like remote login to that computer to fail (timeout). It also affects BonJour Remote Printing. I had to undo the change to the plist. manually removing the <string>-DisableSleepProxyClient</string>. Sorry about this. If I could retract the post, I would.

I've got the exact same problem as you. My Mac wakes from sleep every two hours since upgrading to Yosemite. And I've got the same reason given in Console.

Same/similar issue.

Oct 20 16:29:39 kernel[0] <Notice>: Wake reason: RTC (Alarm)

Oct 20 16:29:39 kernel[0] <Notice>: AppleCamIn::systemWakeCall - messageType = 0xE0000340

Oct 20 16:29:39 kernel[0] <Notice>: AppleThunderboltNHIType2::prePCIWake - power up complete - took 1 us

Oct 20 16:29:43 kernel[0] <Notice>: AppleThunderboltGenericHAL::earlyWake - complete - took 4358 milliseconds

Oct 20 16:29:44 kernel[0] <Notice>: AppleCamIn::handleWakeEvent_gated

Oct 20 16:30:04 kernel[0] <Notice>: ARPT: 3331.330078: AirPort_Brcm43xx::powerChange: System Wake - Full Wake/ Dark Wake / Maintenance wake

Oct 20 16:30:04 kernel[0] <Notice>: AppleCamIn::systemWakeCall - messageType = 0xE0000340

Oct 20 16:30:08 kernel[0] <Notice>: AppleCamIn::handleWakeEvent_gated

Oct 20 16:30:51 kernel[0] <Notice>: AppleCamIn::systemWakeCall - messageType = 0xE0000340

Oct 20 16:30:51 kernel[0] <Notice>: AppleBCM5701Ethernet [en3]: 0 0 memWrInd fBJP_Wakeup_Timer

Oct 20 16:30:53 kernel[0] <Notice>: AppleCamIn::systemWakeCall - messageType = 0xE0000340

Same here. MacPro early 2008.

This only started after upgrading to Yosemite.

Apple, please fix!

Yes I get the same thing on my 2008 mac pro. It wakes from sleep about every 2 hours. It does some thinking, then goes back to sleep. Probably not a issue with a macbook or imac. But these older mac pro's make a **** of a racket firing up all 5+ fans at 3am:(

I did a fresh install on a new hdd. No other software installed. All sharing options, including wake for ethernet is turned off.

I'll bee booting of the mavericks drive for a few more months until Apple solves this.

Googling this issue, gets plenty of results. It's pretty widespread. I'm surprised Apple did not catch this one during testing.

see:

System Preferences > Energy Saver > Enable Power Nap

My model MacPro doesn't support Power Nap so that doesn't even show in Energy Saver.

Power Nap is not the problem anyway. I have it off on my Mini, as do a lot of other people. It's almost definitely a bug, based on the multiple threads about it. It's specific to Yosemite. I'm just hoping it gets fixed soon.

There are some quick fixes for it that require changes in the Terminal, or plist files, but I'm weary of doing those. I'm willing to wait for an official fix; hopefully one arrives within a week or two.

Same here on an 2009 Mac Pro even with everything switched off in energy saver and no applications running.

Others have even tried clean installs to solve it but it persists so it seems to be an OS X bug unless this is now considered normal behaviour.

It is related to the new discoveryd process as it is possible to stop it by editing a plist (see here http://ispire.me/fix-yosemite-rtc-alarm-wakeup-issue/) however this causes other problems so we have to hope an official fix comes soon....

I hope Apple is listening and comes out with a fix for this quickly in the form of a Yosemite 10.10.1 update or something.

Wake for network access is off too?