Unix: Adding a user and a group

Adding a Group:

#addgroup group_name

Adding a User:

#useradd -m -g group_name -s /bin/bash user_name

Options:
-m: created home directory for a user i.e. /home/user_name .It will throw an error if this directory is already existing. Also, it wil create enviorment files for that user in this directory
-g: specifies the group in which user will be added
-s: specifies the default shell for the user