Yesterday, I un-installed the long time not used Byobu. I couldn't even image that this could be the reason of why I could not login to Ubuntu 11.10 today.
I tried many times to login as usually, however, every time, the login was aborted and the screen came back to the login screen user account list again and again.
I tried to login with my root account - fortunately, I created the root user account. When checking the file .xsession-errors under my user account home folder, it sounds the trouble is caused by a line in ~/.profile.
~/.profile line 75: .: filename argument required .: usage: . filename [arguments]
In the ~/.profile
line 75, the command is as following.
. $(which byobu-launch)
After I deleted the line, I could login as usual again.
It was too bad that un-install the Byobu could lead to this big trouble. It sounds for some reasons, the un-install of byobu doesn't clean up this line in the ~/.profile file!