MacOS – How to free up space to reinstall macOS (Catalina)

First I have to explain the gpt result:

The partition with index 1 is your EFI partition. The partitions with index 2 and 3 are your main OS X volume named Macintosh HD (also visible in the second screenshot) and your Recovery HD. The partition with the index 4 is your NTFS volume WinB (also visible in the second screenshot).

Trying to add a new partition (by using the +-button) or to resize Macintosh HD (by using the handle) with Disk Utility will downsize partition 2 and move partition 3 to the new end of partition 2.

Since adding a new partition with the +-button doesn't work properly for you, you have two options:

• use the handle and resize Macintosh HD. This should create unallocated free space

• or use the +-button and create a new volume. Apparently it will be formatted as a HFS+ Journaled volume.

  • Then boot to Internet Recovery Mode and open Terminal.
  • Enter diskutil list and gpt -r show /dev/disk0.
  • Unmount your main disk with diskutil umountDisk /dev/disk0.
  • Remove the new HFS+ volume with gpt and its index number found above:
    gpt remove -i 4 disk0
  • Enter exit and quit Terminal
  • Reboot

This might break Boot Camp as stated in Disk Utility and is not recommended if Windows boots in MBR-mode. So backup your Mac (including the Bootcamp partition) first.

I tested this with a spare MacBook Air (Mid 2013 with a 250 GB SSD) and a vanilla Yosemite after installing Windows 8.1 R1. Regardless what I did, I had no problem to boot from either Windows 8.1 or OS X. Windows 8.1 seems to be booted in EFI-mode though.

Since you have an older Mac, Windows will probably be booted in hybrid MBR-mode. Adding a fourth partition (at position 3) will break bootability of the last one because only three partitions (and the EFI partition) are allowed.

Boot to Recovery Mode (hold cmdR while booting). In the menubar open Utilities -> Terminal.

Now change your working directory and go to /Volumes:

cd /Volumes

List all volumes:

ls -l

Move to your main volume

cd name_of_main_volume

Now you can move forward to a directory to remove files and folders with cd folder_name.

Appropriate paths to remove files or folders without touching your own data are:

/Volumes/name_of_main_volume/cores
/Volumes/name_of_main_volume/var/vm

Then remove files with rm file_name or rm *.* after making sure you are in the proper directory with pwd and checking all files with ls -l.

The folder cores may be empty, vm usually contains a sleep image and/or swap files which are all disposable.

If this doesn't suffice go to your applications or your user folder and remove files/folders.

To remove a folder use rm -R folder_name. In this case application files (e.g. Maps.app) are also folders!