Let's paint a picture here - you've finally downloaded the Windows 10 ISO, opened up the Apple Bootcamp Assistant and then selected your ISO. Everything is fine until you're presented with an error message.
Your disk could not be partitioned
OK, it turned out Google was telling me it was a space issue and that I needed to clear out space on my disk in order to install the OS.
I happily navigate to Disk Utility to find out how much space I have left on my disk, but wait...
I have more than enough space on the disk to install Windows 10, it couldn't be cached data or anything as Disk Utility would report this to me.
After a bit more digging it turned out Time Machine now stores shadow copy snapshots on the local disk ready to transfer when necessary - in order to make space on the disk for Bootcamp I will need to clear out my local snapshot data.
The first step is to turn off Time Machine backups to ensure no further snapshots are created during this process, to do this - simply navigate to
System Preferences > Time Machine
Then uncheck the "Back Up Automatically" setting. After you have done this we can move on to the next step, which is to clear out the snapshot data.
Open up Terminal on your Mac - you'll be presented with the white terminal to enter commands.
The first command is to list all the local snapshots you have for Time Machine on your machine - enter your password if asked.
sudo tmutil listlocalsnapshots /Volumes/
You may have a large list of snapshots listed, to clear these down you will need to run the next command which will remove any unnecessary snapshots.
sudo tmutil thinlocalsnapshots / 999999999999
It may take some time but after the command has finished doing its job you'll see output similar to the below output
Thinned local snapshots:
com.apple.TimeMachine.2018-06-01-185918
com.apple.TimeMachine.2018-06-01-200319
com.apple.TimeMachine.2018-06-01-210426
com.apple.TimeMachine.2018-06-01-220330
com.apple.TimeMachine.2018-06-01-230304
com.apple.TimeMachine.2018-06-02-000339
com.apple.TimeMachine.2018-06-02-124914
com.apple.TimeMachine.2018-06-02-134420
com.apple.TimeMachine.2018-06-02-144517
com.apple.TimeMachine.2018-06-02-164815
com.apple.TimeMachine.2018-06-02-174818
com.apple.TimeMachine.2018-06-02-184856
Now, if you re-run the first command you'll see that there may still be one more snapshot that is leftover
sudo tmutil listlocalsnapshots /Volumes/
The output for this command will show
Sandeeps-MacBook-Pro:~ sandeep$ sudo tmutil listlocalsnapshots /Volumes/
com.apple.TimeMachine.2018-05-25-205927
This last snapshot will need to be deleted, to do this I can run the following command - this will require me to enter the name of the snapshot exactly to what is written in the above list.
Sandeeps-MacBook-Pro:~ sandeep$ sudo tmutil deletelocalsnapshots 2018-05-25-205927
Deleted local snapshot '2018-05-25-205927'
If done correctly you'll see a comment telling you that the snapshot you requested was deleted.
After running these commands we should be good to go! I can now go ahead and install Windows 10 via Boot Camp without any issues.
