<div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> This might be a little reckless without more information on why that lock file is there and empty, but if this were me, I would just delete that lock file and see what happens. (If you break it, you get to keep both halves, so it's all good anyhow) sudo rm /etc/gshadow.lock If you really want to be safe, you can reboot in single user/recovery mode before doing this. But I can't imagine what process would legitimately be keeping a lock on the gshadow file, and I think this must just be something left over from a very badly timed unclean shutdown. </blockquote></div> sudo rm /etc/gshadow.lock Only this command worked! I just deleted gshadow.lock file and the problem got solved! However I don't know about its creation (why did it get created?) and the purpose of it after being getting created! Thx.