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If you want to do a straight migration you can start the socket unit and expose it via the DOCKER_HOST environment variable and use the standard docker tooling

If you want to do a straight migration you can start the socket unit and expose it via the DOCKER_HOST environment variable and use the standard docker tooling or use podman-docker to make it seamless. As long as you make no other changes everything should just work. Where people frequently run into issues is when they want to utilize the rootless feature, and that definitely requires adjustments and work.

robinhoodexe 4y ago
Rootless is definitely one of the major selling points for using podman over docker, especially for local development.
- Lutger 4y ago
  Isn't there support for rootless docker these days as well?
  - 5e92cb50239222b 4y ago
    I never used it, but have seen separate "rootless" images many times. Seems like you have to build a separate image for rootless Docker? podman runs regular images under an unprivileged user just fine.
    - plonk 4y ago
      You don't need a separate image. You can run a script to install a rootless systemd service that starts the Docker daemon. You just point the Docker client to that rootless daemon's socket and do things as before. You'll need some configuration if you want to expose system ports (below 1024).
timost 4y ago
Using DOCKER_HOST and the podman-docker package (Debian and Ubuntu) also makes it really easy to use docker-compose which is more mature and feature-complete than podman-compose.
itsthejb 4y ago
If you’re on regular docker and would like to go podman for rootless, you can take the middle step of migrating to rootless docker. Essential step, honestly - it’s significant work to get rootless working (but definitely worth it) Haven’t done so myself yet, but rootless docker to podman ought to be more or less a direct switch
dbrgn 4y ago
I agree, rootless was also the main blocker when I attempted my last migration in June. My goal was to run all my Docker containers as rootless Podman containers through systemd. The first service I ported was single-container, which made it easier. Still quite some work (like manually adjusting the podman-generated unit file, tracking down some weird-looking error messages, etc), but doable. Once you get to multi-container setups, I ran into even more issues (IIRC related to the linking of containers through a network, while staying rootless), so I gave up for the moment and started a Docker daemon for the rest of the services...

robinhoodexe 4y ago

Rootless is definitely one of the major selling points for using podman over docker, especially for local development.

Lutger 4y ago
Isn't there support for rootless docker these days as well?
- 5e92cb50239222b 4y ago
  I never used it, but have seen separate "rootless" images many times. Seems like you have to build a separate image for rootless Docker? podman runs regular images under an unprivileged user just fine.
  - plonk 4y ago
    You don't need a separate image. You can run a script to install a rootless systemd service that starts the Docker daemon. You just point the Docker client to that rootless daemon's socket and do things as before. You'll need some configuration if you want to expose system ports (below 1024).

timost 4y ago

Using DOCKER_HOST and the podman-docker package (Debian and Ubuntu) also makes it really easy to use docker-compose which is more mature and feature-complete than podman-compose.

itsthejb 4y ago

If you’re on regular docker and would like to go podman for rootless, you can take the middle step of migrating to rootless docker. Essential step, honestly - it’s significant work to get rootless working (but definitely worth it) Haven’t done so myself yet, but rootless docker to podman ought to be more or less a direct switch

dbrgn 4y ago

I agree, rootless was also the main blocker when I attempted my last migration in June. My goal was to run all my Docker containers as rootless Podman containers through systemd. The first service I ported was single-container, which made it easier. Still quite some work (like manually adjusting the podman-generated unit file, tracking down some weird-looking error messages, etc), but doable. Once you get to multi-container setups, I ran into even more issues (IIRC related to the linking of containers through a network, while staying rootless), so I gave up for the moment and started a Docker daemon for the rest of the services...