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 Configuration
OS: 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 100000
SUB_UID_MAX 600100000
SUB_UID_COUNT 65536
SUB_GID_MIN 100000
SUB_GID_MAX 600100000
SUB_GID_COUNT 65536
After
SUB_UID_MIN 100000
SUB_UID_MAX 600100000
SUB_UID_COUNT 100000
SUB_GID_MIN 100000
SUB_GID_MAX 600100000
SUB_GID_COUNT 100000
then 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
