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How are UID and Gid numbers used in Unix?
The Unix-systems use UID and GID numbers to map usernames and groupnames to numbers. For both groups there is an identical set of numbers that van be used, and they are treated as different entities. Due to this setup groupnames and usernames can be the same, or can be different and have the same number.
How does UID work in different Docker containers?
So you can’t have different users with the same uid inside different containers. That’s because the username (and group names) that show up in common linux tools aren’t part of the kernel, but are managed by external tools (/etc/passwd, LDAP, Kerberos, etc).
How are UID and Gid numbers used in samba?
On Windows-like systems (Windows, SAMBA) we have more or less the same problem, which is overcome by using Domains. Another type of problem arises if you want to mix Unix-like systems with Windows-like systems. The Unix-systems use UID and GID numbers to map usernames and groupnames to numbers.
What is the UID of Marc in Docker?
I built a Docker image that has a user named “appuser” and this user has a defined uid of 1001. On my test server, the account I’m using is named “marc”, and it also has the uid of 1001.
How are UIDs assigned on a different system?
UIDs from this range are automatically assigned to any home directory discovered, and persisted locally on first login. On different systems the same user might get different UIDs assigned in case of conflict, though it is attempted to make UID assignments stable, by deriving them from a hash of the user name.
Are there any special UIDs for Linux systemd?
However, four UIDs are special on Linux: 65534 → The nobody UID, also called the “overflow” UID or similar. It’s where various subsystems map unmappable users to, for example file systems only supporting 16bit UIDs, NFS or user namespacing.