The overall docs for this are: https://systemd.io/USER_GROUP_API/
The drop-in persistent store is json formatted files, though the underlying API allows several backend storage mechanisms. If you use systemd-homed, the backend is an encrypted json file in your home directory. If you use the NSS interface, it's using the normal built in Linux/Unix password database API. It also supports SSSD. It's also not isolated to using one, but will check all the defined sources. And if you feel up to it, you can write you own varlink solution. ________________________________________ From: systemd-devel <[email protected]> on behalf of Mantas Mikulėnas <[email protected]> Sent: Monday, August 31, 2026 9:08 AM To: Stef Bon <[email protected]> Cc: systemd Mailing List <[email protected]> Subject: [EXTERNAL] Re: [systemd-devel] Howto create mount and user namespace? On Mon, Aug 31, 2026, 12: 38 Stef Bon <stefbon@ gmail. com> wrote: Oh, I've already read that the local database for users does not have to be openldap but systemd userdb. I'm discovering a lot of functionality I'm not aware of. On Mon, Aug 31, 2026, 12:38 Stef Bon <[email protected]> wrote: Oh, I've already read that the local database for users does not have to be openldap but systemd userdb. I'm discovering a lot of functionality I'm not aware of. Looking at manpage of systemd-homed. Still issues: - what is userdb actually? Is a it ldbm database? A bunch of .json files, if I remember correctly. (AFAIK it's very much meant for "one/few users per system" setups, not like LDAP.) - howto deal with usernames which are email addresses? You know Linux internally does not support a @ in a name. No, it definitely does.
