How do I find out why my computer hangs during logout?

Question

I use multiple user accounts on my Mac (For security purposes, make sensitive/private information physically inaccessible in certain contexts).

If I start and shutdown the computer in a normal single-user flow, everything works fine. But if I am logged in with both user accounts at the same time, i.e. I switch account without logging out first, then I am unable to log out from any account.

I can switch fine between each logged in account; but logging out, and therefore also shutdown/restart doesn't work.

The screen goes black, and the computer just hangs. No keyboard or mouse interaction have any observable effect. I am left with a forced shutdown by holding the power button.

I have not yet tried making an SSH connection from a third computer; which I guess could help identify the cause of the problem; but I don't know what to look for either.

I assume that it's some deadlock in a program that is running once for each user account, but how do I determine which?

Answer 1

Usually when a GUI program stops logout by failing to quit on signal, you get an alert dialog, but that’s not happening here. I would start by logging in and then immediately trying to log out without doing anything else. If you still get the hang, then something that starts automatically is causing the problem. Otherwise, make a list of all the programs you launch after logging in and start a binary search; i.e., eliminate half of them and test, then the other half, then half of those you haven’t eliminated, and so on.

You may be able to speed up the process by logging out remotely instead of forcing a reboot:

ssh admin@host sudo launchctl bootout user/hunguid

where “admin” is the name of a local admin user and “hunguid” is the numerical user ID of the hung user. If you have set up remote login as root, you can do that and skip the sudo part.

Instead of all that, you could try querying the log remotely while the machine is hung, but I doubt you would find anything useful.

Answer 2

If I understand correctly you are logged in to two accounts at same time and then go to shutdown in one of them without logging out of one of the accounts. If that's the case then it'll take time or hang for that matter.

Think for a minute: you have two accounts logged in so essentially its like running two windows on the same machine. Each account has stuff running like Edge Updater running in background etc.. or Chrome.

If you just logout w/o closing these apps it'll cause more issues cause before it can shutdown it has to close those apps or store it in cache. If in essence you want to open it again at the next login so two accounts with Chrome open with different config.

If you haven't closed Chrome and you hit shutdown most likely Chrome has a message that says are you sure you want to close but because you don't see the message because your computer is in the midst of shutting down. It hangs because it cant close said app because of said box you cant confirm and say yes to close (Chrome is just a example as far as I know Chrome asks but I know Vivaldi does and Steam client, too.)

((maybe try closing all apps in both logins then logout of one login then try shutting down))