Time Machine not doing hourly backups on El Capitan

SBeattie2 wrote:

For those interested in trying the "defaults write" solution - here it is ...

For completeness sake, to return the preference file to its previous state, removing the "RequiresACPower" key/value pair, you should be able to use this:

sudo defaults delete /Library/Preferences/com.apple.TimeMachine RequiresACPower

You might want to do that prior to applying the next El Capitan update, just in case it has some undesired effect, or just to see if the update itself adds that key. The defaults read command will tell you if the key exists after the update. You can reapply it again if needed using the defaults write command. As always, be careful when using Terminal commands, particularly sudo ones, to make sure the command is entered correctly. It is very important not to omit any spaces.

Regarding undesired effects, the only thing I can think of is if RequiresACPower is set to false, a Time Machine backup might occur when the power is out & the Mac (& probably the TM backup drive) would be powered by the UPS. If the UPS battery runs down during the backup, it might leave the backup drive in an unusual state. I think it could probably recover on the next backup, but I'm not sure about that.

The delete option is a good catch. Although I didn't feel that it was necessary - but you never know. Thanks for providing it. My thinking is that the primary purpose of a UPS is to shutdown the mac cleanly - while the UPS still has sufficient power to perform that task - more so than to keep the Mac up and running during a power outage. Most likely the external backup drive is also on UPS power. The UPS would force the Mac to do a clean shutdown when the battery remaining (or time remaining) falls below a set threshold. The Mac would begin shutdown operations and force the Time Machine backup to abort (cleanly) before the Mac would shutdown. The drive would continue to be powered by the UPS until the ups battery runs out completely. Upon restart and subsequent run of TIme Machine - the aborted backup would most likely be recovered and/or started over by Time Machine. Keep in mind that a much harsher abnormal termination occurs quite frequently on Mac portables and Time Machine recovers successfully (at least from all of my prior observations. If it did not recover - there would be a very large group of Mac portable users with corrupt backups - and then Time Machine would be deemed unstable resulting in nobody using it..

This bug is an unfortunate problem impacting a critical backup process that typically should not be tinkered with in an unconventional manner. The fix - unfortunately has equal ramifications and side effects specific to each Mac installation. It requires careful thought to implement as well as observation and validation after implanting the fix. I would expect that someone who is willing to implement the workarounds in this discussion - is also going to use some level of diligence to determine if the fix is suitable for their specific configuration - and not just blindly implement the "fix"..

~Scott

Apple has updated my bug report with a note indicating that this problem has been addressed in the 10.11.2 beta. They did not provide any further details. Unfortunately I cannot test the 10.11.2 beta myself - as I am only having the problem on my late 2012 Mac Mini Server and I don't have the original 10.11.(0) installer to reproduce the problem elsewhere. Hopefully somebody that is following this thread can confirm that the 10.11.2 beta will actually fix the problem.

~Scott

Why couldn’t one just trash the modified .plist file and let the system recreate the default before updating?

lkrupp wrote:

Why couldn’t one just trash the modified .plist file and let the system recreate the default before updating?

You could, but that would also erase any Time Machine preferences you had previously set to anything other than the default values, like items excluded via the Privacy pane.

SBeattie2 wrote:

Hopefully somebody that is following this thread can confirm that the 10.11.2 beta will actually fix the problem.

~Scott

My MBP running 10.11.2 Beta 5 does do the hourly backups.

db24401 - Since you are on a MBP - you will need to ensure that you have "unchecked" the option in time machine preferences to "Allow Backups While on Battery" - otherwise you aren't actually doing a valid test of whether 10.11.2 beta has fixed the problem ... and ... you also had to previously have the problem (which occurs only for people who updated from Yosemite to El Capitan using the original 10.11 update). Users that upgraded from Yosemite using the subsequent 10.11.1 version - would not have encountered the problem. Also - the current 10.11.1 release "will NOT" fix the problem created by the 10.11 original El Capitan. A clean install of 10.11.1 (and presumably 10.11.2 beta) - however- also avoids the problem.

Can you confirm that you meet all of these conditions before saying that 10.11.2 beta actually fixes the problem?

~Scott

iKrupp - The problem is not with the plist file. There is actually nothing wrong with the plist - the problem is elsewhere - however - the line added to the plist file (mentioned earlier in this thread) - is tricking Time Machine into thinking it can run while on battery - and normally desktop Macs do not have this line in the plist file. Seems that the problem is with Time Machine querying the power state (when a battery is present - either in a Mac Portable - or Desktop with a UPS) - and thinking the Mac is running on battery when it actually running on AC power. Could be something as simple as a permission issue somewhere - just a guess. You will also notice similar behavior with File Vault encryption pausing on a desktop when a UPS is present - because it thinks it is running on battery. The File Vault pause issue is only on Desktops and not portables - and is actually NOT corrected by 10.11.1 (even a clean install) - it's a similar problem - and a separate bug. As stated by R C-R - you can in-fact trash the time machine plist file - and it will recreate - and you will have to re-do your time machine config - and it will not fix the backup issue.

~Scott

On iMac (Mid 2010) with 10.11.1 (clean install) and APC UPS I got the same problem with the hourly Time Machine backups.

Now I upgraded to 10.11.2 -> New problem with plugged APC UPS: iMac hangs on startup (50–60%).

Upgraded to OS 10.11.2 on my Late 2015 iMac and UPS/USB problem with Time Machine is fixed. Automatic backups work now. Not having any startup issues.

I just upgraded to 10.11.2 and I still have the same problem as before. Backup disk shows as a normal disk on desktop, automatic backups no longer happen, no problem initiating it manually. I do have a UPS but "enable/disable backups when on battery" does not show up in my Time Machine options.

I tried SBeattie2's thing and while it reported successful editing, it did not fix anything.

Hi EVLMedia - I am about to apply the 10.11.2 update to my one remaining MacMini that is having the problem. This machine is using an APC BackUPS XS 1500 (although I believe the UPS brand is irrelevant here). I had to undo my plist fix - first - and reboot to ensure that I could get the problem to reappear - and I did. The "allow backups while on battery" option only appears in Time Machine preferences for Mac portables (e.g. MacBook Pro/MacBook Air - where there is a built in battery present).

If you did my suggested plist fix correctly - and you completely shutdown and rebooted with the UPS cable attached - it should have allowed your backups to run. Keep in mind - the plist fix typically doesn't kick in until the 2nd hourly backup time is reached and the backup should begin running hourly at that point. For some reason - after making the plist change - the first hourly backup seems to be skipped - and then everything is fine after that. If you are making a determination by watching only for the first hourly backup to run - that is not a valid indication of the problem having occurred. I think you will see it start up after the second cycle. Since you have already update to 10.11.2 - I would say to remove the plist fix - reboot - allow the machine to run beyond the first two expected hour backup times - before determining success or failure.

The most efficient way to make the plist fix (if 10.11.2 doesn't fix the problem) is to use the defaults write command - no need to manipulate the plist file manually. The link below shows that particular post within this thread. I want to point out that other people (in my circle of acquaintances) have used the plist fix and it has worked for them - I have not received any reports of it not working. But supposedly with 10.11.2 - this should not be necessary.

Re: Time Machine not doing hourly backups on El Capitan

Also - have you attempted to completely shutdown your UPS using its power button - removing the UPS data cable from the Mac - and then performing an SMC reset. Keep in mind - if you boot the Mac without the UPS data cable attached - and then attach the UPS data cable post-boot - the backup problem does not occur - until the next reboot with the cable in place.

~Scott

Then you have a completely different issue than the one being discussed here. Take a look at Time Machine logs using the Console app. in the Utilities folder.

rj-vij - on all of my 10.11.1 clean installs (on Mac Desktops with APC UPS's) - I also did an SMC reset. Have you tried an SMC reset?

Hersco - Over the course of time that this thread has been going on - I have seen a few circumstances where a reboot - with the UPS data cable attached - does not encounter the backup problem - and I am not sure if it has anything to do with actually physically powering down the UPS. However - the problem inevitably returns on a subsequent reboot. Can you confirm that 10.11.2 has truly fixed your problem by doing at least two more reboots? Unfortunately it may take quite a few hours of watching the backups to ensure that they are in-fact running hourly - and also not checking until after the second expected hourly backup has passed it time to run.

~Scott