When running for example sbtn on a given user, a temp '/tmp/.sbt/ipcsocket ' directory will be created and it will be owned by that user.
Any other user will be unable to run sbtn, because he will not have write permission on that folder.
The temp folder should be something like /tmp/.sbt-$USER/ipcsocket to avoid these kinds of issues.
The culprit is in https://github.com/sbt/ipcsocket/blob/ee3439303e592846168a3b18f23358d3c6665949/src/main/java/org/scalasbt/ipcsocket/NativeLoader.java