How can I changing user password on Ubuntu 14.04

This question was answered by @gblanchard4:

To change a users password you need to have sudo privileges yourself. sudo passwd username will change the password for the ‘username’ you want to change.

You can see the comment here.

This question was answered by @sheriffderek:

To list users you can use this terminal command (when you are logged in…)

cut -d: -f1 /etc/passwd

That being said… you are going to see a great many usernames you do not recognize… and those are system users that are needed to perform certain tasks - so you do not want to delete them.

You can check your users against these:

root daemon bin sys sync games man lp mail news uucp proxy www-data backup list irc gnats nobody libuuid syslog messagebus landscape sshd colord sheriffderek mysql

Where ‘root’ and ‘sheriffderek’ - are the only usernames I was previously aware of… so - your additional users should be in addition to these.

Also, you should just delete the users you don’t want instead of just changing the passwords. It’s just as easy to create new ones.

This is what I found when I googled your question:

http://askubuntu.com/questions/410244/a-command-to-list-all-users-and-how-to-add-delete-modify-users

ps: can you change your question title to - ‘How may I reset a user’s password: Ubuntu 14.04’ - or something that is a little more clear, for others. : )

You can see the comment here.