Linux: Add existing user to a group

usermod -a -G wheel cyrus cyrus is in group cyrus, to add cyrus to another group use the -a option. If you only use -G option only, cyrus will transfer group from cyrus to wheel.

Arch Linux: Add group and add normal user

Add a group groupadd cyrus -g 1000 To verify: cat /etc/group Add user and put to group cyrus useradd cyrus Verify the account cat /etc/passwd Understand the sequence of passwd file username:password:UID:GID:Name:Home directory:shell Clear text password does not store in /etc/passwd, password is salted and hashed and stored in /etc/shadow file.