Group Accounts

Users can belong to one or more groups, which affects system access and permissions.

Key Points

  • Primary Group: Defined in /etc/passwd.
  • Secondary Groups: Defined in /etc/group.
  • Modern Linux: Users can belong to over 65,000 groups (older UNIX limited to 16).
  • Group names vs. GID: Names are for humans; system uses numeric GID internally.

Example : alt text

Field Example Description
Group Name mail Name of the group, easier to remember than the numeric GID.
Password Placeholder x Indicates group password is not stored here (rarely used).
GID 12 Unique numeric ID of the group.
User List mail,postfix Members of the group (secondary membership).