:PROPERTIES:
:ID:       bad088c8-2c15-4033-863e-b33ecb940674
:END:
#+title: Command line: Podman
#+date: "2021-06-10 11:51:26 +08:00"
#+date_modified: "2021-07-20 23:31:29 +08:00"
#+language: en
#+property: header-args  :eval no


Podman is a daemonless container engine.
It was also designed to be a drop-in replacement for Docker with similar command-line interface and everything.
Thus, it is also compatible with Docker images and configurations (i.e., Dockerfiles).




* Configuring to include =docker.io=

By default, Podman focuses on making the user concious about multiple registries outside DockerHub.
Thus, it doesn't have any by default.
You have to configure it first.
For more information, see the =podman.1= manual page and the linked pages.

Here's an incredibly simple example configuration that includes DockerHub.

#+begin_src toml
unqualified-search-registries = ['docker.io']
#+end_src



* Subcommands

Podman has Git-style command-line interface with subcommands and exclusive options.

- =build= is for building images from the configuration — e.g., ~podman build .~ will build an image from the current directory with the Dockerfile.
  + =-t, --tag [NAME]= attaches a tag to the image.
  + =-f, --file [FILE]= sets the name of the Dockerfile to be built from.

- =run= will create a container from an image.
  + =-d, --detach= will make the process run in the background.
  + =-it= will make an interactive shell.
  + =-p, --publish= exposes the port of the image to the host.

- =tag= will tag an existing image.
  Useful for correcting tags for pushing into a remote registry.

- =image= is anything about interaction with images.
  In fact, a lot of the subcommands presented so far are aliases with =image= being the original — e.g., =image tag= vs =tag=, =image pull= vs =pull=, =image rm= vs =rmi=.




* Examples

Podman is a big tool so it needs a big list of examples.


** Quickstart for pushing a container

As with big tools, comes with a big quickstart.

#+begin_src shell
# Builds an image from the Dockerfile of the current directory.
podman build --tag todo-list-web-app .

# List the images to see if our app image has been built.
podman image list

# Assuming the app creates an HTTP server at port 5000, we'll expose it to the host, making it accessible from there.
podman run -d -p 5111:5000 todo-list-web-app

# See if we did run a containerized version of our app.
podman container list

# Tag the image with the convention seen in Docker registry.
podman tag foodogsquared/python-helloworld:v1.0.0

# Push the image to the Docker registry (assuming you've already logged in to Docker registry).
podman push foodogsquared/python-helloworld
#+end_src


** Interactive selection of removing images

What would be an example script without something like [[id:4eb1f8b1-bc12-4a6c-8fa4-20e4c3542cf2][fzf]]?

#+begin_src bash
podman image list --format "{{.ID}} {{.Repository}} {{.Tag}}" \
    | fzf --multi --prompt "Choose images to remove > " \
    | awk '{print $1}' \
    | xargs podman image rm
#+end_src


** Interactive image search and install

Yes, another one with fzf...

#+begin_src bash
podman image search --format "{{.Index}} {{.Name}}" alpine \
    | fzf --multi --prompt "Choose images to install > " \
    | awk '{print $2}' \
    | xargs podman image pull
#+end_src