systemd-imdsd@.service

systemd

systemd-imdsd

systemd-imdsd.socket

systemd-imdsd-early-network.service

Cloud IMDS (Instance Metadata Service) client

systemd-imdsd@.service

systemd-imdsd.socket

systemd-imdsd-early-network.service

/usr/lib/systemd/systemd-imdsd

Description

systemd-imdsd@.service is a system service that provides local access to IMDS (Instance Metadata Service; or equivalent) functionality, as provided by many public clouds.

The service provides a Varlink IPC interface via /run/systemd/io.systemd.InstanceMetadata to query IMDS fields.

systemd-imdsd-early-network.service is a system service that generates a systemd-networkd.service(8) compatible systemd.network(5) file for configuring the early-boot network in order to be able to contact the IMDS endpoint.

The systemd-imds(1) tool may be used to query information from this service.

Kernel Command Line Options

The IMDS endpoint is typically determined automatically via hwdb(7) records, but can also be configured explicitly via the kernel command line, via the following options:

systemd.imds.network=
Takes one of off, locked, unlocked. Controls whether and how to set up networking for IMDS endpoint access. Unless set to off early boot networking is enabled, ensuring that the IMDS endpoint can be reached. If set to locked direct access to the IMDS endpoint by regular unprivileged processes is disabled via a "prohibit" route, so that any access must be done through systemd-imdsd@.service or its associated tools. If set to unlocked (the default) this "prohibit" route is not created, and regular unprivileged processes can directly contact IMDS.

systemd.imds.vendor=
A short string identifying the cloud vendor.

Example:

systemd.imds.vendor=foobarcloud

systemd.imds.token_url=
If a bearer token must be acquired to talk to the IMDS service, this is the URL to acquire it from.

systemd.imds.refresh_header_name=
Takes a HTTP header field name (excluding the :) that declares the header field for passing the TTL value (in seconds) to the HTTP server when acquiring a token. Only applies if systemd.imds.token_url= is set too.

systemd.imds.data_url=
Takes the base URL to acquire the IMDS data from (the IMDS "endpoint"). All data fields are acquired from below this URL. This URL should typically not end in /.

The data URLs are concatenated from this base URL, the IMDS "key" and the suffix configured via systemd.imds.data_url_suffix= below. Well-known IMDS "keys" can be configured via the systemd.imds.key=* options below.

Example:

systemd.imds.data_url=http://169.254.169.254/metadata

systemd.imds.data_url_suffix=
If specified, this field is appended to the end of the data URL (after appending the IMDS "key" to the data base URL), see above.

Example:

systemd.imds.data_url_suffix=?api-version=2025-04-07&format=text

systemd.imds.token_header_name=
Takes a HTTP header field name (excluding the :) that declares the header field to pass the bearer token acquired from the token URL (see above) in. Only applies if systemd.imds.token_url= is set too.

systemd.imds.extra_header=
Takes a full HTTP header expression (both field name and value, separated by a colon :) to pass to the HTTP server when requesting data. May be used multiple times to set multiple headers.

Example:

systemd.imds.extra_header=Metadata:true

systemd.imds.address_ipv4=
Configures the IPv4 address the IMDS endpoint is contacted on. This should typically be the IP address also configured via systemd.imds.data_url= (if IPv4 is used) and is used to set up IP routing.

Example:

systemd.imds.address_ipv4=169.254.169.254

systemd.imds.address_ipv6=
Configures the IPv6 address the IMDS endpoint is contacted on. This should typically be the IP address also configured via systemd.imds.data_url= (if IPv6 is used) and is used to set up IP routing.

systemd.imds.key.hostname=; systemd.imds.key.region=; systemd.imds.key.zone=; systemd.imds.key.ipv4_public=; systemd.imds.key.ipv6_public=; systemd.imds.key.ssh_key=; systemd.imds.key.userdata=; systemd.imds.key.userdata_base=; systemd.imds.key.userdata_base64=
Configures strings to concatenate to the data base URL (see above) to acquire data for various "well-known" fields. These strings must begin with a /. They should return the relevant data in plain text.

A special case are the three "userdata" keys: the option systemd.imds.key.userdata_base= should be used if the IMDS service knows a concept of multiple userdata fields, and a field identifier thus still needs to be appended to the userdata base URL. The option systemd.imds.key.userdata= should be used if only a single userdata field is supported. The option systemd.imds.key.userdata_base64= should be used in the same case, but only if the userdata field is encoded in Base64.

Example:

systemd.imds.key.hostname=/instance/compute/osProfile/computerName

Credentials

systemd-imdsd@.service supports the service credentials logic as implemented by ImportCredential=/LoadCredential=/SetCredential= (see systemd.exec(5) for details). The following credentials are used when passed in:

imds.vendor; imds.vendor_token; imds.refresh_header_name; imds.data_url; imds.data_url_suffix; imds.token_header_name; imds.extra_header; imds.extra_header2; imds.extra_header3; imds.extra_header…; imds.address_ipv4; imds.address_ipv6; imds.key_hostname; imds.key_region; imds.key_zone; imds.key_ipv4_public; imds.key_ipv6_public; imds.key_ssh_key; imds.key_userdata; imds.key_userdata_base; imds.key_userdata_base64
The various IMDS endpoint parameters. The semantics are very close to those configurable via kernel command line, see above for the matching list.