I think that this is the way how simple special linux tools work. Someone would prefer some complex tool, which would display blocking processes, give chance to kill them, or filter the list and kill just some of them… A lot can be done. But KISS, umount just umounts, it does not conversate a lot with user. Process list can be very long, but you do not start umount to get some list of processes. You start it to umount… If it can not, it says it can not. You know what to do (find blocking processes, check their state, think about them, ask mom, kill some, let some running… and finally umount -l πŸ™‚ You can do a lot, but umount is a simple tool for umounting, not for listing processes. Should it list pids? Or names? Or complex lines like ps -ef does?…. There already are appropriate tools like fuser and ps to do this for you, why umount should? Think about this. But I understand, listing pids would be useful, maybe with -v switch. Maybe even umount does not know pids πŸ˜€ I did not check sources.