How to change user passwords in Ubuntu

You need to create a password for the first account. This can be done with the passwd command. You will be prompted to enter your old password once and enter your new password two times.
Change user Paul's password with the root user
[[email protected] root]# passwd user name (Paul)
Changing password for user Paul. New Password:
Retype new PASSWORD:PASSWD:
All authentication tokens updated successfully.
[Email protected] root]#

Users may change their own passwords later. This example shows that the user Paul has no privileges to change his password.
[Email protected] paul]$ passwd
Changing password for Paul old Password:your current password
Enter the new password (minimum of 5, maximum of 8 characters)
Please use a combination of upper and lower case letters and numbers.
New Password:your New Password
Re-enter new Password:your New password
Password changed.
[Email protected] paul]$

How to change user passwords in Ubuntu