"Error: It looks like another Unity instance is running with this project open"

Sometimes when my project chashes and I try to open it again show this message. Usually I restart the OS to solve this. My quesiont is: How can I tell unity that there is not project left? killing a process? modifying a file?
I am a bit worried about trying to end a process and killing the unity ubuntu user interface.

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When Unity closes unexpectedly it fails to delete a temporary file that prevents another instance of unity to open the same project. This file is located at [ProjectRootFolder]/Temp/UnityLockFile. So, you need to delete that file in order to open the project again without restarting the OS.

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Same issue here… but the UnityLock file still exist because not all process are closed right.

ps ax | grep Unity
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ah thanks for explanation and for the command line help!

Also on a side to a the above, if you have your debugger attached to the process you get this. I need to close down mono or vsc

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Awesome thanks! Deleting UnityLock fixed my issue. Side note, I first had to go into task manager > details, and force close Unity.exe before I could delete UnityLock.

We cannot do either on some of our computers, and when we do e still get the same error message.

@kentg1 - is the project on a shared network drive?? If so you may need to find the other machine that is accessing the project. .

Looks like Unity has fixed this problem - I got a email form tech support a few days ago saying that they would address it