How do I eject the Time Machine backup drive automatically after each backup?

Question

How do I set Time Machine to eject my external Time Machine backup drive automatically after each backup?

Answer 1

There might be a better way, but one solution might be to Applescript it. I haven't yet found any way to run an applescript after a backup, but you could:

1. Turn off automatic TM backup
2. Set up an applescript to run TM
   • Some googling turned up this line to force an immediate TM build: do shell script "/System/Library/CoreServices/backupd.bundle/Contents/Resources/backupd-helper >/dev/null 2>&1 &"
3. Add a line to eject the disk afterwards.
   • eject disk somedrivename

If you want this to happen on a regular basis, you could attach it to a cron job.

Answer 2

~/bin/timemachine:

#!/bin/bash

d="Time Machine"        
diskutil mount "$d" && tmutil startbackup -b && diskutil eject "$d"

~/Library/LaunchAgents/timemachine_eject.plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC -//Apple Computer//DTD PLIST 1.0//EN http://www.apple.com/DTDs/PropertyList-1.0.dtd>
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>timemachine_eject</string>
    <key>Program</key>
    <string>/Users/username/bin/timemachine</string> <!-- ~/ doesn't work -->
    <key>StartInterval</key>
    <integer>120</integer> <!-- run every two minutes for testing -->
</dict>
</plist>

Make the script executable, unload the default plist, and load the new one:

chmod +x ~/bin/timemachine
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.backupd-auto.plist
launchctl load ~/Library/LaunchAgents/timemachine_eject.plist

To apply changes to the plist, you have to unload and load it.

Answer 3

Haven't tried this, but it looks like it might work:

Jettison (Mac App Store link)

Ejects external drives when going to sleep and remounts them waking from sleep.