[ubuntu] Unable to login in ubuntu

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http://ubuntuforums.org – Hi, I have installed ubuntu 12.04 on VMWARE Workstation. Today I performed some upgrade on ubuntu to install Oracle 11g on it. After installing updates, I restarted it. Since then I am not able to login to ubuntu. Admin user ID of ubuntu is ubuntu1204. But when I check /etc/passwd from guest login it does not show the user in that file. While login it does not give any error message as well. Please help in resolving the issue. Thanks. (Hardware)