How to change shell from /bin/bash to /bin/zsh?

Question

I am trying to change from /bin/bash to /bin/zsh but I get this...

$ chsh
Password:
Changing the login shell for user_name
Enter the new value, or press ENTER for the default
Login Shell [/bin/bash]: /bin/zsh
chsh: user 'username' does not exist in /etc/passwd
$

I checked /etc/passwd, there is no entry for my username. Also, we use likewise-open for authentication on LDAP.

Please help.