Ubuntu Manpage: podman-system-service

NAME

       podman-system-service - Run an API service

SYNOPSIS

       podman system service [options]

DESCRIPTION

The podman system service command creates a listening service that answers API calls for Podman. The
command is available on Linux systems and is usually executed in systemd services. The command is not
available when the Podman command is executed directly on a Windows or macOS host or in other situations
where the Podman command is accessing a remote Podman API service.

The REST API provided by podman system service is split into two parts: a compatibility layer offering
support for the Docker v1.40 API, and a Podman-native Libpod layer. Documentation for the latter is
available at https://docs.podman.io/en/latest/_static/api.html. Both APIs are versioned, but the server
does not reject requests with an unsupported version set.

Run the command in a systemd service
The command podman system service supports systemd socket activation. When the command is run in a
systemd service, the API service can therefore be provided on demand. If the systemd service is not
already running, it will be activated as soon as a client connects to the listening socket. Systemd then
executes the podman system service command. After some time of inactivity, as defined by the --time
option, the command terminates. Systemd sets the podman.service state as inactive. At this point there
is no podman system service process running. No unnecessary compute resources are wasted. As soon as
another client connects, systemd activates the systemd service again.

The systemd unit files that declares the Podman API service for users are

• /usr/lib/systemd/user/podman.service

• /usr/lib/systemd/user/podman.socket

In the file podman.socket the path of the listening Unix socket is defined by

ListenStream=%t/podman/podman.sock

The path contains the systemd specifier %t which systemd expands to the value of the environment variable
XDG_RUNTIME_DIR (see systemd specifiers in the systemd.unit(5) man page).

In addition to the systemd user services, there is also a systemd system service podman.service. It runs
rootful Podman and is accessed from the Unix socket /run/podman/podman.sock. See the systemd unit files

• /usr/lib/systemd/system/podman.service

• /usr/lib/systemd/system/podman.socket

The podman system service command does not support more than one listening socket for the API service.

Note: The default systemd unit files (system and user) change the log-level option to info from error.
This change provides additional information on each API call.

Run the command directly
To support running an API service without using a systemd service, the command also takes an optional
endpoint argument for the API in URI form. For example, unix:///tmp/foobar.sock or tcp://localhost:8080.
If no endpoint is provided, defaults is used. The default endpoint for a rootful service is
unix:///run/podman/podman.sock and rootless is unix://$XDG_RUNTIME_DIR/podman/podman.sock (for example
unix:///run/user/1000/podman/podman.sock)

Access the Unix socket from inside a container
To access the API service inside a container: - mount the socket as a volume - run the container with
--security-opt label=disable

Security
Please note that the API grants full access to all Podman functionality, and thus allows arbitrary code
execution as the user running the API, with no ability to limit or audit this access. The API's security
model is built upon access via a Unix socket with access restricted via standard file permissions,
ensuring that only the user running the service will be able to access it. TLS can be used to secure
this socket by requiring clients to present a certificate signed by a trusted certificate authority
("CA"), as well as to allow the client to verify the identity of the API. We strongly recommend against
making the API socket available via the network (IE, bindings the service to a tcp URL) without enabling
mutual TLS to authenticate the client. Even access via Localhost carries risks - anyone with access to
the system will be able to access the API. If remote access is required, we instead recommend forwarding
the API socket via SSH, and limiting access on the remote machine to the greatest extent possible. If a
tcp URL must be used without TLS, using the --cors option is recommended to improve security.

OPTIONS

   --cors
       CORS headers to inject to the HTTP response. The default  value  is  empty  string  which  disables  CORS
       headers.

   --help, -h
       Print usage statement.

   --time, -t
       The  time  until the session expires in seconds. The default is 5 seconds. A value of 0 means no timeout,
       therefore the session does not expire.

   --tls-cert=path
       Path to a PEM file containing the TLS certificate to present to clients. --tls-key must also be provided.

   --tls-client-ca=path
       Path to a PEM file containing  the  TLS  certificate  bundle  to  validate  client  connections  against.
       Connections  that present no certificate or a certificate not signed by one of these certificates will be
       rejected.

   --tls-key=path
       Path to a PEM file containing the private key matching --tls-cert. --tls-cert must also be provided.

       The default timeout  can  be  changed  via  the  service_timeout=VALUE  field  in  containers.conf.   See
       containers.conf(5) for more information.

EXAMPLES

       Start the user systemd socket for a rootless service.

       systemctl --user start podman.socket

       Configure  DOCKER_HOST  environment  variable  to  point  to the Podman socket so that it can be used via
       Docker API tools like docker-compose.

       $ export DOCKER_HOST=unix://$XDG_RUNTIME_DIR/podman/podman.sock
       $ docker-compose up

       Configure the systemd socket to be automatically started after reboots, and run as the specified user.

       systemctl --user enable podman.socket
       loginctl enable-linger <USER>

       Start the systemd socket for the rootful service.

       sudo systemctl start podman.socket

       Configure the socket to be automatically started after reboots.

       sudo systemctl enable podman.socket

       It is possible to run the API without using systemd socket activation.  In this case the API will not  be
       available  on  demand  because  the command will stay terminated after the inactivity timeout has passed.
       Run an API with an inactivity timeout of 5 seconds without using socket activation.

       podman system service --time 5

       The default socket was used as no URI argument was provided.

       Run an API service with a custom socket path and no timeout:

       podman system service --time 0 unix:///var/run/mypodman.sock

       This starts the API service listening on the custom  socket  /var/run/mypodman.sock  with  no  inactivity
       timeout (runs indefinitely).

HISTORY