When systemd-imds is invoked as a Varlink service (via the new
systemd-imds-metrics.socket), it now acts as an io.systemd.Metrics
provider for systemd-report. It connects to systemd-imdsd over the
existing io.systemd.InstanceMetadata interface to acquire the real
data and re-exposes the detected cloud vendor plus the well-known
hostname, region, zone and public IPv4/IPv6 fields as metrics in the
io.systemd.InstanceMetadata.* namespace.
The metrics logic lives entirely on the client side
(imds-tool-metrics.c); systemd-imdsd is unchanged. Each metric is
acquired on demand with a blocking call to the daemon, benefiting from
its local cache. Fields that are unset or unsupported by the vendor are
simply omitted.
The metrics socket is statically enabled into sockets.target.wants/.
This is a client tool to the systemd-imdsd@.service added in the
previous commit. It's mostly just a 1:1 IPC client via Varlink. It can
be used to query any IMDS key, but it's primary usecase is to acquire
the "userdata" from IMDS. Moreover, if invoked with the --import switch
it will check if the userdata contains a list of system credentials. If
so, it will import them into the local credstore. If the userdata does
not look like a list of system credentials no operation is executed,
under the assumption the data is intended for cloud-init instead.
It also imports a couple of other fields, if available and recogniuzed,
such as SSH keys and the hostname.
Lennart Poettering