Sometimes, you need to put a non-interactive passwords using scripts, as you can see, you can’t use passwd tool, because it only works using interactive way.
chpasswd reads a list of user name and password pairs from standard input and uses this information to update a group of existing users. Each line is of the format:
By default the supplied password must be in clear-text. Default encryption algorithm is DES. Also the password age will be updated, if present.
This command is intended to be used in a large system environment where many accounts are created at a single time.
The options which apply to the chpasswd command are:
--encrypted -- Supplied passwords are in encrypted form.
--help -- Display help message and exit.
--md5 -- Use MD5 encryption instead of DES when the supplied passwords are not encrypted
Check passwords using the following command
echo “user:pass” | chpasswd