The -aG option in the usermod command stands for:
-a: This option stands for "append." It allows you to add the user to the supplementary group(s) without removing them from other groups they are already a member of.-G: This option specifies the group(s) to which the user should be added. You can list multiple groups separated by commas.
So, when you use usermod -aG farmers worker1, it adds worker1 to the farmers group while keeping any existing group memberships intact.
