You may have heard that Podman V2 has a new RESTful API. This document demonstrates the API using code examples in Python and shell commands. Additional notes are included in the code comments. The provided code was written to be clear vs. production quality.
Requirements
- You have Python >3.4 installed.
- You have installed the Python requests library.
- An IDE for editing Python is recommended.
- Two terminal windows: one for running the Podman service and reviewing debugging information, the second window to run scripts.
- Usage of curl and jq commands are demonstrated.
- You can review connection URLs here.
Getting started
The service
For these examples, we are running the Podman service as a normal user and on an unsecured TCP/IP port number.
For production, the Podman service should use systemd's socket activation protocol. This allows Podman to support clients without additional daemons and secure the access endpoint.
The following command runs the Podman service on port 8080 without timing out. You will need to type ^C into this terminal window when you are finished with the tutorial.
# podman system service tcp:localhost:8080 --log-level=debug --time=0
In addition to the TCP socket demonstrated above, the Podman service supports running under systemd's socket activation protocol and Unix domain sockets (UDS).
[ You might also like: Sneak peek: Podman's new REST API ]
Python code
Info resource
The following shows us information about the Podman service and host:
import json
import requests
response = requests.get("http://localhost:8080/v1.40.0/libpod/info")
Deep dive
requests.get()
calls the requests library to pass the URL to the Podman service using the GET HTTP method.- The requests library provides helper methods for all the popular HTTP methods.
http://localhost:8080
matches the Podman service invocation above./v1.40.0
denotes the API version we are using./libpod
denotes that we expect the service to provide alibpod
-specific return payload.- Not using this element causes the server to return a compatible payload.
/info
specifies the resource we are querying.
Interesting to read, but without output, how do we know it worked?
Getting output
Append the lines below, and you can now see the version of Podman running on the host:
response.raise_for_status()
info = json.loads(response.text)
print(info.version.Version)
raise_for_status()
raises an exception if status code is not between 200 and 399.json.loads()
decodes the body of the HTTP response into an object/dictionary.
When executed, the output is:
2.1.0-dev
The following works from the shell:
$ curl -s 'http://localhost:8080/v1.40.0/libpod/info' | jq .version.Version
"2.1.0-dev"
Listing containers
import json
import requests
response = requests.get("http://localhost:8080/v1.40.0/libpod/containers/json?all=true")
response.raise_for_status()
ctnrs = json.loads(response.text)
for c in ctnrs:
print(c.Id)
json.loads()
decodes the HTTP body into an array of objects/dictionaries, the program then prints each container Id. For example:
$ curl -s 'http://localhost:8080/v1.40.0/libpod/containers/json?all=true' | jq .[].Id
"81af11ef7188a826cb5883330525e44afea3ae82634980d68e4e9eefc98d6f61"
If the query parameter all=true had not been provided, then only the running containers would have been listed. The resource queries and parameters for the API are documented here.
Something useful
We've looked at a couple of examples, but how about something a little more useful? You have finished developing the next great container, and the script below will remove everything from your local storage. (If you want to save on typing clean_storage.py)
#!/usr/bin/env python
import json
import requests
# Clean up local storage by removing all containers, pods, and images. Any error will
# abort the process
confirm = input("Really delete all items from storage? [y/N] ")
if str(confirm).lower().strip() != 'y':
exit(0)
# Query for all pods in storage
response = requests.get("http://localhost:8080/v1.40.0/libpod/pods/json")
response.raise_for_status()
pods = json.loads(response.text)
# Workaround for https://github.com/containers/podman/issues/7392
if pods is not None:
for p in pods:
# For each container: delete container and associated volumes
response = requests.delete(f"http://localhost:8080/v1.40.0/libpod/pods/{p['Id']}?force=true")
response.raise_for_status()
print(f"Removed {len(pods)} pods and associated objects")
else:
print(f"Removed 0 pods and associated objects")
# Query for all containers in storage
response = requests.get("http://localhost:8080/v1.40.0/libpod/containers/json?all=true")
response.raise_for_status()
ctnrs = json.loads(response.text)
for c in ctnrs:
# For each container: delete container and associated volumes
print(c.keys())
response = requests.delete(f"http://localhost:8080/v1.40.0/libpod/containers/{c['Id']}?force=true&v=true")
response.raise_for_status()
print(f"Removed {len(ctnrs)} containers and associated objects")
# Query for all images in storage
response = requests.get("http://localhost:8080/v1.40.0/libpod/images/json")
response.raise_for_status()
imgs = json.loads(response.text)
for i in imgs:
# For each image: delete image and any associated containers
response = requests.delete(f"http://localhost:8080/v1.40.0/libpod/images/{i['Id']}?force=true")
response.raise_for_status()
print(f"Removed {len(imgs)} images and associated objects")
[ Getting started with containers? Check out this free course. Deploying containerized applications: A technical overview. ]
Summary
I hope you find this helpful. The API documentation provides you with all the resources and required methods. The input and output bodies are included as well as the status codes.
The Podman code is under heavy development and we welcome your input with issues and pull requests on the project's GitHub page.
Sull'autore
Experienced senior software developer/system administrator with 37 years of technical experience. Deep understanding of UNIX/Linux, TCP/IP networking, Internet and software development. Has worked for a diverse set of organizations from large government agencies (NASA, NARA) to 5 person startups. Always applying experience and knowledge to solve the technical challenges of the organization.
Designing and implementing SAS applications (Cloud) on a RAIN architecture with innovative indexing technology for supporting the business rules and logic. This allows for both high performance and horizontal scaling. Examples: DICOM Grid, Inc, and Red Hat OpenShift.
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