Kali Linux:Cannot Log In Account

PROBLEM

After a reboot,I type in my user name and password as usual.It seems that I log in successfully but the screen turn into black and back to the logging interface at once.And no matter how many times I tried,it cycled again and again.

SOLUTION

I searched the Internet and it may be the /etc/profile file goes wrong,which is exactly where I add one line myself.

So I logged in under the recovery mode and delete the line I added.

REBOOT,BING GO!