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I just installed Ubuntu 13.10 on VMware. I am trying to login to root from my user account using su command but unable to login as Terminal is saying the following :

su: Authentication Failed
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up vote 6 down vote accepted

By default, the Root account password is locked in Ubuntu. This means that you cannot login as Root directly or use the su command to become the Root user. However, since the Root account physically exists it is still possible to run programs with root-level privileges. This is where sudo comes in - it allows authorized users (normally "Administrative" users; for further information please refer to AddUsersHowto) to run certain programs as Root without having to know the root password.

So if you want root access then you can use sudo with user, which you have specified during installation. you can run root command like sudo command then it will ask for password.

Update :: To unlock root account

As @JosephR. suggested in comment, we can still become root or set root password using

sudo su

then we can run passwd command to set password.

Referent Link

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You can still become root with sudo su and then set a password for root with passwd. – Joseph R. Jan 12 '14 at 20:28
I know that you know of course. I meant this as a useful addition to your answer in case the OP really needs to become root. – Joseph R. Jan 12 '14 at 21:35
@JosephR. sorry.. for my misunderstanding.. and thanks.. I'm just adding that content. – Rahul Patil Jan 12 '14 at 21:43

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