When you do an upgrade of MacOS, it can be hard to locate the download package as it caches to disk.

Sometimes you may want to see the progress of the download, the size of the file or just troubleshoot an issue with the upgrade process. The following steps show you what commands to run to identify the path of the installer.

1. Login to your Mac, open System Preferences, Software Update and start the update process
2. Launch the Terminal app and change to root by running sudo su and enter your local admin password
3. Maximise your Terminal to fit the screen. The next command needs as much screen real estate as possible
4. Once you are root, run fs_usage -f filesys . This will enumerate all active disk I/O on the system. Data will be printed to the console very quickly, so once you see something with a path containing InstallAssistant.pkg.partial you can press Ctrl+C to break
5. If you can see the entire path that references the InstallAssistant.pkg, then all good, jump to step 10. If not, do the following to locate the full path
6. With the part of the path that you can see, you should see a random string, that may look something like this puuz6c0epc7o0ozyovvi6tjxhzpf6uf04. Use the find command to locate the full path by running the following:
7. find / -name "puuz6c0epc7o0ozyovvi6tjxhzpf6uf04" 2>&1 | grep -v "Operation not permitted"
8. Note that we remove results from the search that result in “Operation not permitted” so that we can reduce search noise
9. After some time, we should see something like  /private/var/folders/zz/zyxvpxvq6csfxvn_n00000s0000068/C/com.apple.SoftwareUpdate/swcdn.apple.com/content/downloads/00/60/071-05432-A_QOY2QE0UMR/puuz6c0epc7o0ozyovvi6tjxhzpf6uf04s/ returned, which is the path we are looking for
10. Now, if you cd to the folder above, you can monitor the download progress on disk with ls -lha
11. After the file has downloaded, it will be moved to /Applications/MacOS "version" install.app and will remain here until the installation has completed. If you want to take a copy of the package, copy it from this location before the install is complete