systemd-homed.service
/usr/lib/systemd/systemd-homed
systemd-homed is a system service that may be used to create, remove, change or inspect home areas (directories and network mounts and real or loopback block devices with a filesystem, optionally encrypted).
Most of systemd-homed's functionality is accessible through the homectl(1) command.
See the m[blue]Home Directoriesm[][1] documentation for details about the format and design of home areas managed by systemd-homed.service.
Each home directory managed by systemd-homed.service synthesizes a local user and group. These are made available to the system using the m[blue]User/Group Record Lookup API via Varlinkm[][2], and thus may be browsed with userdbctl(1).
User records are cryptographically signed with a public/private key pair (the signature is part of the JSON record itself). For a user to be permitted to log in locally the public key matching the signature of their user record must be installed. For a user record to be modified locally the private key matching the signature must be installed locally, too. The keys are stored in the /var/lib/systemd/home/ directory:
/var/lib/systemd/home/local.private
/var/lib/systemd/home/local.public
/var/lib/systemd/home/*.public
All key files listed above are in PEM format.
In order to migrate a home directory from a host "foobar" to another host "quux" it is hence sufficient to copy /var/lib/systemd/home/local.public from the host "foobar" to "quux", maybe calling the file on the destination /var/lib/systemd/home/foobar.public, reflecting the origin of the key. If the user record should be modifiable on "quux" the pair /var/lib/systemd/home/local.public and /var/lib/systemd/home/local.private need to be copied from "foobar" to "quux", and placed under the identical paths there, as currently only a single private key is supported per host. Note of course that the latter means that user records generated/signed before the key pair is copied in, lose their validity.
systemd(1), homed.conf(5), homectl(1), pam_systemd_home(8), userdbctl(1), org.freedesktop.home1(5)