Using the following two commands will allow you to add either a new user or an existing user to correct permissions issues that you may encounter in a Linux OS.
Adding A New User To A Usergroup
Log into your Linux server via SSH / Shell.
Since we are going to be adding a new user to an existing group, you can do this by typing one command instead of first creating the user and then adding it to the usergroup. To add the new user, type the following;
"useradd -G user group"
Adding An Existing User To A Usergroup
Since the user already exists you will now need to use the "usermod" command. Any attempt to add an existing user will result in an error using the "useradd" command.
To add the user to the usergroup, type the following;
"usermod -a -G user group"
