bindings

README

Podman Golang bindings

The Podman Go bindings are a set of functions to allow developers to execute Podman operations from within their Go based application. The Go bindings connect to a Podman service which can run locally or on a remote machine. You can perform many operations including pulling and listing images, starting, stopping or inspecting containers. Currently, the Podman repository has bindings available for operations on images, containers, pods, networks and manifests among others.

Quick Start

The bindings require that the Podman system service is running for the specified user. This can be done with systemd using the systemctl command or manually by calling the service directly.

Starting the service with system

The command to start the Podman service differs slightly depending on the user that is running the service. For a rootful service, start the service like this:

# systemctl start podman.socket

For a non-privileged, aka rootless, user, start the service like this:

$ systemctl start --user podman.socket

Starting the service manually

It can be handy to run the system service manually. Doing so allows you to enable debug messaging.

$ podman --log-level=debug system service -t0

If you do not provide a specific path for the socket, a default is provided. The location of that socket for rootful connections is /run/podman/podman.sock and for rootless it is /run/user/USERID#/podman/podman.sock. For more information about the Podman system service, see man podman-system-service.

Creating a connection

Ensure the required dependencies are installed, as they will be required to compile a Go program making use of the bindings.

The first step for using the bindings is to create a connection to the socket. As mentioned earlier, the destination of the socket depends on the user who owns it. In this case, a rootful connection is made.

import (
	"context"
	"fmt"
	"os"

	"github.com/containers/podman/v4/pkg/bindings"
)

func main() {
	conn, err := bindings.NewConnection(context.Background(), "unix://run/podman/podman.sock")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}

}

The conn variable returned from the bindings.NewConnection function can then be used in subsequent function calls to interact with containers.

Examples

The following examples build upon the connection example from above. They are all rootful connections as well.

Note: Optional arguments to the bindings methods are set using With*() methods on *Option structures. Composite types are not duplicated rather the address is used. As such, you should not change an underlying field between initializing the *Option structure and calling the bindings method.

Inspect a container

The following example obtains the inspect information for a container named foorbar and then prints the container's ID. Note the use of optional inspect options for size.

import (
	"context"
	"fmt"
	"os"

	"github.com/containers/podman/v4/pkg/bindings"
	"github.com/containers/podman/v4/pkg/bindings/containers"
)

func main() {
	conn, err := bindings.NewConnection(context.Background(), "unix://run/podman/podman.sock")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	inspectData, err := containers.Inspect(conn, "foobar", new(containers.InspectOptions).WithSize(true))
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	// Print the container ID
	fmt.Println(inspectData.ID)
}

Pull an image

The following example pulls the image quay.ioo/libpod/alpine_nginx to the local image store.

import (
	"context"
	"fmt"
	"os"

	"github.com/containers/podman/v4/pkg/bindings"
	"github.com/containers/podman/v4/pkg/bindings/images"
)

func main() {
	conn, err := bindings.NewConnection(context.Background(), "unix://run/podman/podman.sock")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	_, err = images.Pull(conn, "quay.io/libpod/alpine_nginx", nil)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
}

Pull an image, create a container, and start the container

The following example pulls the quay.io/libpod/alpine_nginx image and then creates a container named foobar from it. And finally, it starts the container.

import (
	"context"
	"fmt"
	"os"

	"github.com/containers/podman/v4/pkg/bindings"
	"github.com/containers/podman/v4/pkg/bindings/containers"
	"github.com/containers/podman/v4/pkg/bindings/images"
	"github.com/containers/podman/v4/pkg/specgen"
)

func main() {
	conn, err := bindings.NewConnection(context.Background(), "unix://run/podman/podman.sock")
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	_, err = images.Pull(conn, "quay.io/libpod/alpine_nginx", nil)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	s := specgen.NewSpecGenerator("quay.io/libpod/alpine_nginx", false)
	s.Name = "foobar"
	createResponse, err := containers.CreateWithSpec(conn, s, nil)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	fmt.Println("Container created.")
	if err := containers.Start(conn, createResponse.ID, nil); err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	fmt.Println("Container started.")
}

Debugging tips

To debug in a development setup, you can start the Podman system service in debug mode like:

$ podman --log-level=debug system service -t 0

The --log-level=debug echoes all the logged requests and is useful to trace the execution path at a finer granularity. A snippet of a sample run looks like:

INFO[0000] podman filtering at log level debug
DEBU[0000] Called service.PersistentPreRunE(podman --log-level=debug system service -t0)
DEBU[0000] Ignoring libpod.conf EventsLogger setting "/home/lsm5/.config/containers/containers.conf". Use "journald" if you want to change this setting and remove libpod.conf files.
DEBU[0000] Reading configuration file "/usr/share/containers/containers.conf"
DEBU[0000] Merged system config "/usr/share/containers/containers.conf": {Editors note: the remainder of this line was removed due to Jekyll formatting errors.}
DEBU[0000] Using conmon: "/usr/bin/conmon"
DEBU[0000] Initializing boltdb state at /home/lsm5/.local/share/containers/storage/libpod/bolt_state.db
DEBU[0000] Overriding run root "/run/user/1000/containers" with "/run/user/1000" from database
DEBU[0000] Using graph driver overlay
DEBU[0000] Using graph root /home/lsm5/.local/share/containers/storage
DEBU[0000] Using run root /run/user/1000
DEBU[0000] Using static dir /home/lsm5/.local/share/containers/storage/libpod
DEBU[0000] Using tmp dir /run/user/1000/libpod/tmp
DEBU[0000] Using volume path /home/lsm5/.local/share/containers/storage/volumes
DEBU[0000] Set libpod namespace to ""
DEBU[0000] Not configuring container store
DEBU[0000] Initializing event backend file
DEBU[0000] using runtime "/usr/bin/runc"
DEBU[0000] using runtime "/usr/bin/crun"
WARN[0000] Error initializing configured OCI runtime kata: no valid executable found for OCI runtime kata: invalid argument
DEBU[0000] using runtime "/usr/bin/crun"
INFO[0000] Setting parallel job count to 25
INFO[0000] podman filtering at log level debug
DEBU[0000] Called service.PersistentPreRunE(podman --log-level=debug system service -t0)
DEBU[0000] Ignoring libpod.conf EventsLogger setting "/home/lsm5/.config/containers/containers.conf". Use "journald" if you want to change this setting and remove libpod.conf files.
DEBU[0000] Reading configuration file "/usr/share/containers/containers.conf"

If the Podman system service has been started via systemd socket activation, you can view the logs using journalctl. The logs after a sample run look like:

$ journalctl --user --no-pager -u podman.socket
-- Reboot --
Jul 22 13:50:40 nagato.nanadai.me systemd[1048]: Listening on Podman API Socket.
$

$ journalctl --user --no-pager -u podman.service
Jul 22 13:50:53 nagato.nanadai.me systemd[1048]: Starting Podman API Service...
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: time="2020-07-22T13:50:54-04:00" level=error msg="Error refreshing volume 38480630a8bdaa3e1a0ebd34c94038591b0d7ad994b37be5b4f2072bb6ef0879: error acquiring lock 0 for volume 38480630a8bdaa3e1a0ebd34c94038591b0d7ad994b37be5b4f2072bb6ef0879: file exists"
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: time="2020-07-22T13:50:54-04:00" level=error msg="Error refreshing volume 47d410af4d762a0cc456a89e58f759937146fa3be32b5e95a698a1d4069f4024: error acquiring lock 0 for volume 47d410af4d762a0cc456a89e58f759937146fa3be32b5e95a698a1d4069f4024: file exists"
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: time="2020-07-22T13:50:54-04:00" level=error msg="Error refreshing volume 86e73f082e344dad38c8792fb86b2017c4f133f2a8db87f239d1d28a78cf0868: error acquiring lock 0 for volume 86e73f082e344dad38c8792fb86b2017c4f133f2a8db87f239d1d28a78cf0868: file exists"
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: time="2020-07-22T13:50:54-04:00" level=error msg="Error refreshing volume 9a16ea764be490a5563e384d9074ab0495e4d9119be380c664037d6cf1215631: error acquiring lock 0 for volume 9a16ea764be490a5563e384d9074ab0495e4d9119be380c664037d6cf1215631: file exists"
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: time="2020-07-22T13:50:54-04:00" level=error msg="Error refreshing volume bfd6b2a97217f8655add13e0ad3f6b8e1c79bc1519b7a1e15361a107ccf57fc0: error acquiring lock 0 for volume bfd6b2a97217f8655add13e0ad3f6b8e1c79bc1519b7a1e15361a107ccf57fc0: file exists"
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: time="2020-07-22T13:50:54-04:00" level=error msg="Error refreshing volume f9b9f630982452ebcbed24bd229b142fbeecd5d4c85791fca440b21d56fef563: error acquiring lock 0 for volume f9b9f630982452ebcbed24bd229b142fbeecd5d4c85791fca440b21d56fef563: file exists"
Jul 22 13:50:54 nagato.nanadai.me podman[1527]: Trying to pull registry.fedoraproject.org/fedora:latest...
Jul 22 13:50:55 nagato.nanadai.me podman[1527]: Getting image source signatures
Jul 22 13:50:55 nagato.nanadai.me podman[1527]: Copying blob sha256:dd9f43919ba05f05d4f783c31e83e5e776c4f5d29dd72b9ec5056b9576c10053
Jul 22 13:50:55 nagato.nanadai.me podman[1527]: Copying config sha256:00ff39a8bf19f810a7e641f7eb3ddc47635913a19c4996debd91fafb6b379069
Jul 22 13:50:55 nagato.nanadai.me podman[1527]: Writing manifest to image destination
Jul 22 13:50:55 nagato.nanadai.me podman[1527]: Storing signatures
Jul 22 13:50:55 nagato.nanadai.me systemd[1048]: podman.service: unit configures an IP firewall, but not running as root.
Jul 22 13:50:55 nagato.nanadai.me systemd[1048]: (This warning is only shown for the first unit using IP firewalling.)
Jul 22 13:51:15 nagato.nanadai.me systemd[1048]: podman.service: Succeeded.
Jul 22 13:51:15 nagato.nanadai.me systemd[1048]: Finished Podman API Service.
Jul 22 13:51:15 nagato.nanadai.me systemd[1048]: podman.service: Consumed 1.339s CPU time.
$

You can also verify that the information being passed back and forth is correct by putting with a tool like socat, which can dump what the socket is seeing.

Documentation

Index

• Variables
• func CheckResponseCode(inError error) (int, error)
• func JoinURL(elements ...string) string
• func NewConnection(ctx context.Context, uri string) (context.Context, error)
• func NewConnectionWithIdentity(ctx context.Context, uri string, identity string, machine bool) (context.Context, error)
• func ServiceVersion(ctx context.Context) *semver.Version
• type APIResponse
  • func (h *APIResponse) IsClientError() bool
  • func (h *APIResponse) IsConflictError() bool
  • func (h *APIResponse) IsInformational() bool
  • func (h *APIResponse) IsRedirection() bool
  • func (h *APIResponse) IsServerError() bool
  • func (h *APIResponse) IsSuccess() bool
  • func (h APIResponse) Process(unmarshalInto interface{}) error
  • func (h APIResponse) ProcessWithError(unmarshalInto interface{}, unmarshalErrorInto interface{}) error
• type Connection
  • func GetClient(ctx context.Context) (*Connection, error)
  • func (c *Connection) DoRequest(ctx context.Context, httpBody io.Reader, httpMethod, endpoint string, ...) (*APIResponse, error)
  • func (c *Connection) GetDialer(ctx context.Context) (net.Conn, error)

Variables

var (
	ErrNotImplemented = errors.New("function not implemented")
)

Functions

func CheckResponseCode

func CheckResponseCode(inError error) (int, error)

func JoinURL

func JoinURL(elements ...string) string

JoinURL elements with '/'

func NewConnection

func NewConnection(ctx context.Context, uri string) (context.Context, error)

NewConnection creates a new service connection without an identity

func NewConnectionWithIdentity

func NewConnectionWithIdentity(ctx context.Context, uri string, identity string, machine bool) (context.Context, error)

NewConnectionWithIdentity takes a URI as a string and returns a context with the Connection embedded as a value. This context needs to be passed to each endpoint to work correctly.

A valid URI connection should be scheme:// For example tcp://localhost:<port> or unix:///run/podman/podman.sock or ssh://<user>@<host>[:port]/run/podman/podman.sock?secure=True

func ServiceVersion

func ServiceVersion(ctx context.Context) *semver.Version

ServiceVersion from context build by NewConnection()

Types

type APIResponse

type APIResponse struct {
	*http.Response
	Request *http.Request
}

func (*APIResponse) IsClientError

func (h *APIResponse) IsClientError() bool

IsClientError returns true if the response code is 4xx

func (*APIResponse) IsConflictError

func (h *APIResponse) IsConflictError() bool

IsConflictError returns true if the response code is 409

func (*APIResponse) IsInformational

func (h *APIResponse) IsInformational() bool

IsInformational returns true if the response code is 1xx

func (*APIResponse) IsRedirection

func (h *APIResponse) IsRedirection() bool

IsRedirection returns true if the response code is 3xx

func (*APIResponse) IsServerError

func (h *APIResponse) IsServerError() bool

IsServerError returns true if the response code is 5xx

func (*APIResponse) IsSuccess

func (h *APIResponse) IsSuccess() bool

IsSuccess returns true if the response code is 2xx

func (APIResponse) Process

func (h APIResponse) Process(unmarshalInto interface{}) error

Process drains the response body, and processes the HTTP status code Note: Closing the response.Body is left to the caller

func (APIResponse) ProcessWithError

func (h APIResponse) ProcessWithError(unmarshalInto interface{}, unmarshalErrorInto interface{}) error

ProcessWithError drains the response body, and processes the HTTP status code Note: Closing the response.Body is left to the caller

type Connection

type Connection struct {
	URI    *url.URL
	Client *http.Client
}

func GetClient

func GetClient(ctx context.Context) (*Connection, error)

GetClient from context build by NewConnection()

func (*Connection) DoRequest

func (c *Connection) DoRequest(ctx context.Context, httpBody io.Reader, httpMethod, endpoint string, queryParams url.Values, headers http.Header, pathValues ...string) (*APIResponse, error)

DoRequest assembles the http request and returns the response. The caller must close the response body.

func (*Connection) GetDialer

func (c *Connection) GetDialer(ctx context.Context) (net.Conn, error)

GetDialer returns raw Transport.DialContext from client