Chapter 21. Using the container-tools API

1. Use systemd to activate the Podman API socket.
2. Use a Podman client to perform basic commands.

Procedure

1. Start the service immediately:

   # systemctl enable --now podman.socket

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2. To enable the link to var/lib/docker.sock by using the docker-podman package:

   # dnf install podman-docker

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Verification

1. Display system information of Podman:

   # podman-remote info

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2. Verify the link:

   # ls -al /var/run/docker.sock
   lrwxrwxrwx. 1 root root 23 Nov  4 10:19 /var/run/docker.sock -> /run/podman/podman.sock

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Procedure

1. Enable and start the service immediately:

   $ systemctl --user enable --now podman.socket

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2. Optional: To enable programs by using Docker to interact with the rootless Podman socket:

   $ export DOCKER_HOST=unix:///run/user/<uid>/podman//podman.sock

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Verification

1. Check the status of the socket:

   $ systemctl --user status podman.socket
   ● podman.socket - Podman API Socket
    Loaded: loaded (/usr/lib/systemd/user/podman.socket; enabled; vendor preset: enabled)
   Active: active (listening) since Mon 2021-08-23 10:37:25 CEST; 9min ago
   Docs: man:podman-system-service(1)
   Listen: /run/user/1000/podman/podman.sock (Stream)
   CGroup: /user.slice/user-1000.slice/user@1000.service/podman.socket

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   The podman.socket is active and is listening at /run/user/<uid>/podman.podman.sock, where <uid> is the user’s ID.

2. Display system information of Podman:

   $ podman-remote info

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Procedure

1. Run the service for the REST API:

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

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   • The value of 0 means no timeout. The default endpoint for a rootful service is unix:/run/podman/podman.sock.
   • The --log-level <level> option sets the logging level. The standard logging levels are debug, info, warn, error, fatal, and panic.

2. In another terminal, display system information of Podman. The podman-remote command, unlike the regular podman command, communicates through the Podman socket:

   # podman-remote info

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3. To troubleshoot the Podman API and display request and responses, use the curl comman. To get the information about the Podman installation on the Linux server in JSON format:

   # curl -s --unix-socket /run/podman/podman.sock http://d/v1.0.0/libpod/info | jq
       {
     "host": {
       "arch": "amd64",
       "buildahVersion": "1.15.0",
       "cgroupVersion": "v2",
       "conmon": {
         "package": "conmon-2.0.18-1.module+el8.3.0+7084+c16098dd.x86_64",
         "path": "/usr/bin/conmon",
         "version": "conmon version 2.0.18, commit: 7fd3f71a218f8d3a7202e464252aeb1e942d17eb"
       },
       …
     "version": {
       "APIVersion": 1,
       "Version": "2.0.0",
       "GoVersion": "go1.14.2",
       "GitCommit": "",
       "BuiltTime": "Thu Jan  1 01:00:00 1970",
       "Built": 0,
       "OsArch": "linux/amd64"
     }
   }

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   A jq utility is a command-line JSON processor.

4. Pull the registry.access.redhat.com/ubi10/ubi container image:

   # curl -XPOST --unix-socket /run/podman/podman.sock -v 'http://d/v1.0.0/images/create?fromImage=registry.access.redhat.com%2Fubi10%2Fubi'
   *   Trying /run/podman/podman.sock...
   * Connected to d (/run/podman/podman.sock) port 80 (#0)
   > POST /v1.0.0/images/create?fromImage=registry.access.redhat.com%2Fubi10%2Fubi HTTP/1.1
   > Host: d
   > User-Agent: curl/7.61.1
   > Accept: /
   >
   < HTTP/1.1 200 OK
   < Content-Type: application/json
   < Date: Tue, 20 Oct 2020 13:58:37 GMT
   < Content-Length: 231
   <
   {"status":"pulling image () from registry.access.redhat.com/ubi10/ubi:latest, registry.redhat.io/ubi10/ubi:latest","error":"","progress":"","progressDetail":{},"id":"ecbc6f53bba0d1923ca9e92b3f747da8353a070fccbae93625bd8b47dbee772e"}
   * Connection #0 to host d left intact

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5. Display the pulled image:

   # curl --unix-socket /run/podman/podman.sock -v 'http://d/v1.0.0/libpod/images/json' | jq
   *   Trying /run/podman/podman.sock...
     % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                    Dload  Upload   Total   Spent    Left  Speed
     0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0* Connected to d (/run/podman/podman.sock) port 80 (0) > GET /v1.0.0/libpod/images/json HTTP/1.1 > Host: d > User-Agent: curl/7.61.1 > Accept: / > < HTTP/1.1 200 OK < Content-Type: application/json < Date: Tue, 20 Oct 2020 13:59:55 GMT < Transfer-Encoding: chunked < { [12498 bytes data] 100 12485 0 12485 0 0 2032k 0 --:--:-- --:--:-- --:--:-- 2438k * Connection #0 to host d left intact [ { "Id": "ecbc6f53bba0d1923ca9e92b3f747da8353a070fccbae93625bd8b47dbee772e", "RepoTags": [ "registry.access.redhat.com/ubi10/ubi:latest", "registry.redhat.io/ubi10/ubi:latest" ], "Created": "2020-09-01T19:44:12.470032Z", "Size": 210838671, "Labels": { "architecture": "x86_64", "build-date": "2020-09-01T19:43:46.041620", "com.redhat.build-host": "cpt-1008.osbs.prod.upshift.rdu2.redhat.com", ... "maintainer": "Red Hat, Inc.", "name": "ubi10", ... "summary": "Provides the latest release of Red Hat Universal Base Image 8.", "url": "https://access.redhat.com/containers//registry.access.redhat.com/ubi10/images/8.2-347",
         ...
       },
       "Names": [
         "registry.access.redhat.com/ubi10/ubi:latest",
         "registry.redhat.io/ubi10/ubi:latest"
       ],
       ...
       ]
     }
   ]

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