1. How to add a user:
    2. # useradd -u 100 -g staff -d /export/home/scott -m scott

  where:  -u 100  means UID=100
          -g 10   means GID=10
          -d /export/home/scott is the user's home directory
          -m means "create the directory"
          scott is the user to be created
  2. How to remove a user:
    3. # userdel -r scott

  where:  -r means "remove the user's home directory"
          scott is the user to be deleted
  3. How to change a user's default shell
    4. # usermod -s /usr/bin/bash scott

  where:  /usr/bin/bash is the new shell
          scott is the account to be modified