I am currently managing a Postfix mail server on an Ubuntu system and I am encountering issues with UID and GID assignments for newly created users. Here are the details:
System ConfigurationOS: Ubuntu 22.04,Mail Server: Postfix,User Management: Using useradd command
Issue Description:When I create new users using the useradd -m testuser command, I receive the following error:useradd: Can't get unique subordinate UID range useradd: can't create subordinate user IDs
In the /etc/subuid and /etc/subgid files, there are 62,072 user entries. If I remove any user ID from these files, I can create a new user, and the removed user UID and GID ID's is assigned to the new user profile.
I have edited the /etc/login.defs file to set the UID and GID ranges as follows:
Before SUB_UID_MIN 100000SUB_UID_MAX 600100000SUB_UID_COUNT 65536SUB_GID_MIN 100000SUB_GID_MAX 600100000SUB_GID_COUNT 65536AfterSUB_UID_MIN 100000SUB_UID_MAX 600100000SUB_UID_COUNT 100000SUB_GID_MIN 100000SUB_GID_MAX 600100000SUB_GID_COUNT 100000then also the same issue occurred.1)Why does the error occur when trying to create a new user?2)How should I handle the large number of user entries in the /etc/subuid and /etc/subgid files to ensure new users can be created without conflicts?3)should I change anything in the login.defs config file