My office setup includes two Macintosh computers, a Mac Pro and a MacBook Pro. I have a 500 GB FireWire drive attached to the Mac Pro that I use for TimeMachine backups. Through the power of a DNS entry for the Mac Pro, and this article on Network Time Machine backups to another Mac, I am able to backup the MacBook Pro, wirelessly, to the TimeMachine drive on the Mac Pro.
The only problem with this arrangement is that the MacBook Pro attempts to back itself up regardless of my location. When I’m at home at it is connected to our home network it can locate my work computer (via the DNS entry) and it tries to use our less-than-significant upload bandwidth to backup once an hour. The simple solution is to turn TimeMachine off when I am at home. Of course that means remembering to turn it back on again the next day I’m at work. On occasion the simple solution has meant the MacBook Pros backups are a week or more behind.
A better solution would be a script or automated action that would turn TimeMachine on or off. Since I work relatively stable hours a cron job coupled with code to activate or deactivate TimeMachine would suffice.
You can turn TimeMachine on or off via Terminal using this defaults command:
defaults write /Library/Preferences/com.apple.TimeMachine AutoBackup -boolean [YES|NO]
#!/bin/bash defaults write /Library/Preferences/com.apple.TimeMachine AutoBackup -boolean YES
#!/bin/bash defaults write /Library/Preferences/com.apple.TimeMachine AutoBackup -boolean NO
Here’s my completed crontab:
# minute hour day-of-month month day-of-week what # activate TimeMachine zero minutes past 8 am M-F 0 8 * * 1-5 ~/bin/timeMachineon.sh # deactivate TimeMachine zero minutes past 5 pm (17) M-F 0 17 * * 1-5 ~/bin/timeMachineoff.sh
Update 1: The evening cron job fails to run when the laptop is closed, i.e., sleeping, when 5 pm rolls around. Cron is a useful tool but it has to be awake to run. I’ve changed the evening cron time to 4 pm, a time I am almost always still at work. I am considering adding a second evening crontab entry, say for 7 or 8 pm in case the 4 o’clock instance is missed for some reason. A better solution would be a network aware triggering of the scripts, running the on script only when the work network is detected, and the off script for all other networks.
Update 2: Here’s the latest solution, based on Josh’s comments.
I created a script called login-hook.sh, which is the target of:
sudo defaults write com.apple.loginwindow LoginHook ~/bin/login-hook.sh
#!/bin/bash # login-hook.sh if [ "$(ps ax | grep tm-control.sh | grep -vc grep)" -lt 1 ]; then sudo -u mhn /Users/mhn/bin/tm-control.sh & fi
#!/bin/bash # tm-control.sh while [ 1 ]; do python ~/bin/TM_off_on.py sleep 1800 done