Migration Assistant is one of those things which will either work perfectly (most of the time) and save you much effort, or else will fail in interesting and subtle manners and annoy the heck out of you until you fathom what it did wrong.

Most recently I was migrating someone from a 2007 iMac to a nice new 27″ 5K iMac – quite the update. I only migrated their user account – I tend to reinstall apps from scratch, especially with such a significant migration. All seemed OK at first, but a few issues came up:

• Google Drive would not sync – when double-clicking the App icon it would only open the sync directory, but not actually run
• Latexian could not export a PDF if it involved overwriting an existing file
• The Trash was not working – if you tried to drag something to it the only option was to delete immediately

The first problem turned out to be due to Google Drive having installed various things in ~/Library/Application Support/Google/Drive which were apparently out of date. Deleting this folder and re-running the Drive app sorted that problem out.

The second problem was more subtle, but turned out to be down to incorrect ownership of the user directory. While the username was the same for the new account, the userID number was different. It looks like Migration Assistant created the new account, gave it UID number 502, but created the home directory with the UID 503, which was the UID for the old Mac. All folders within the home directory had the correct ownership, so you were able to read/write properly below that, but nothing new could be created in the home folder, like the .Trashes/ folder. Once I figured this out a quick ‘sudo chown’ fixed things right up.

In summary, to paraphrase President Reagan, one may trust Migration Assistant, but always verify…