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Transitioning from Docker to Podman

developers.redhat.com

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Re: Transitioning from Docker to Podman

#71

Post by dumpsterdiver »

Grollicus wrote: post #28
throwaway894345 wrote: post #18

Earlier quoted context omitted.

I actually like the idea of Docker as a better systemd (or rather, the interface is better). No bespoke file format, programmable API, no need to google for the right journalctl switches, and then of course the advantages of containers and images over processes and system packages. I’m not suggesting everything should be a container nor that docker is the ideal implementation, but it certainly points in the right dir…

Last time i did look into docker it couldn't even tell if a service is up or still starting and there were all kinds of weird hacks around that like "is something listening on the configured port". Did that improve?

Systemd struggles with this as well. While a service can easily tell you if it's "up", sometimes the only way to determine if it's "available" is to check. Keep in mind that the sentinel for any given service will be different. If you think about it, how could any external monitoring service determine when a service under it's purview is available without actually checking?

Maybe it already has something like this, but I feel like systemd could provide an API endpoint for applications to send a simple status when they are "ready" - at which point it would be up to the developers to provide that at the right time.

Re: Transitioning from Docker to Podman

#72

Post by nimbius »

Podman, buildah, and skopeo are insanely awesome tools that let you transition an image from a public registry to your own private deployment in a jiffy. The article doesn't mention it but podman can also dump a pod configuration you can use in kubernetes and open shift/okd so if you're not a yaml wizard you can still get stuff running containerized.

Re: Transitioning from Docker to Podman

#73

Post by felipelemos »

quietbritishjim wrote: post #70
ranadeep wrote: post #22

At my company, we run our CI/CD (Jenkins) using the Docker-in-Docker paradigm to facilitate easy maintainability of the CI itself and allow us to run containerized builds. When we shifted to RHEL 8, we attempted to move this over to Podman and it went miserably (this was back in November 2019). The main reason being is that podman-in-podman doesn't work and had bugs (at least back in Nov 2019). Maybe it fixed now but…

> Docker-in-Docker paradigm Apologies for the patronising comment, but do you really mean that? Docker in Docker works but is intended for the developers of Docker to debug Docker itself. Usually for running Docker from within a container, you just hook up the Docker client to the TCP port of the Docker daemon running outside the container, which isn't strictly Docker-in-Docker. I ask this in case you're trying a wil…

There are some reasons to use docker in docker beyond debug docker itself. For example, in Jenkins case, select specific proxy settings for the daemon for a specific job without affecting other jobs in the same node.

Re: Transitioning from Docker to Podman

#74

Post by solotronics »

quietbritishjim wrote: post #70
ranadeep wrote: post #22

At my company, we run our CI/CD (Jenkins) using the Docker-in-Docker paradigm to facilitate easy maintainability of the CI itself and allow us to run containerized builds. When we shifted to RHEL 8, we attempted to move this over to Podman and it went miserably (this was back in November 2019). The main reason being is that podman-in-podman doesn't work and had bugs (at least back in Nov 2019). Maybe it fixed now but…

> Docker-in-Docker paradigm Apologies for the patronising comment, but do you really mean that? Docker in Docker works but is intended for the developers of Docker to debug Docker itself. Usually for running Docker from within a container, you just hook up the Docker client to the TCP port of the Docker daemon running outside the container, which isn't strictly Docker-in-Docker. I ask this in case you're trying a wil…

I also needed to run docker commands from within a container (Jenkins container executing docker cmds on the host it's running on). I don't know how common this is but I had the same use case.

Re: Transitioning from Docker to Podman

#75

Post by flerchin »

quietbritishjim wrote: post #70
ranadeep wrote: post #22

At my company, we run our CI/CD (Jenkins) using the Docker-in-Docker paradigm to facilitate easy maintainability of the CI itself and allow us to run containerized builds. When we shifted to RHEL 8, we attempted to move this over to Podman and it went miserably (this was back in November 2019). The main reason being is that podman-in-podman doesn't work and had bugs (at least back in Nov 2019). Maybe it fixed now but…

> Docker-in-Docker paradigm Apologies for the patronising comment, but do you really mean that? Docker in Docker works but is intended for the developers of Docker to debug Docker itself. Usually for running Docker from within a container, you just hook up the Docker client to the TCP port of the Docker daemon running outside the container, which isn't strictly Docker-in-Docker. I ask this in case you're trying a wil…

We docker-in-docker too, exactly as OP describes. In jenkins CI/CD.

Re: Transitioning from Docker to Podman

#76

Post by dmix »

oezi wrote: post #68
donor20 wrote: post #65

Earlier quoted context omitted.

Openshift years ago at least (last time I looked) - SHUDDER! I couldn't believe it was what big business / enterprise was standardizing on as best in class. It looks like it's now Kube / Docker connected, but back then I think it did it's own thing? The cost in time / $ / config to maintain and operate at the time was not pretty (all this no doubt has changed a lot).

They gave you three pods for free until they moved to Openshift 3. I ran an entire startup five years using them without paying a single penny. A nice Heroku alternative. (Iot control server, so basically no load)

Openshift was very generous to startups, I can back that up as well.

It always seemed like added complexity to me in exchange for free hosting. I liked the idea in concept more than in practice. But we also weren't big enough to really justify it so eventually we switched to simpler VPS hosting.

Re: Transitioning from Docker to Podman

#78

Post by nhoughto »

quietbritishjim wrote: post #70
ranadeep wrote: post #22

At my company, we run our CI/CD (Jenkins) using the Docker-in-Docker paradigm to facilitate easy maintainability of the CI itself and allow us to run containerized builds. When we shifted to RHEL 8, we attempted to move this over to Podman and it went miserably (this was back in November 2019). The main reason being is that podman-in-podman doesn't work and had bugs (at least back in Nov 2019). Maybe it fixed now but…

> Docker-in-Docker paradigm Apologies for the patronising comment, but do you really mean that? Docker in Docker works but is intended for the developers of Docker to debug Docker itself. Usually for running Docker from within a container, you just hook up the Docker client to the TCP port of the Docker daemon running outside the container, which isn't strictly Docker-in-Docker. I ask this in case you're trying a wil…

Docker in docker is a very common pattern in CI, in some cases is the only way to achieve certain tasks.

Re: Transitioning from Docker to Podman

#79

Post by choeger »

yjftsjthsd-h wrote: post #45
choeger wrote: post #29

Earlier quoted context omitted.

Maybe you are just too far into docker. I noticed that a lot of default workflows (needlessly) depended on docker running with privileges. One big reason for that seem to be Mac users that only know docker from inside a VM. However, if you think about what you're really needing for CI you will easily see that docker-in-docker gains you nothing. You can as well use plain docker (or podman). The same holds for privileg…

Okay, I want to build a container image using gitlab CI, which runs builds in docker. How would you like me to build an image without using docker in docker, or buildah in docker?

Your problem is the assumption that a gitlab CI process requires a docker image. If you do the following, you are fine:

* Switch to a shell runner

* Put the CI dockerfile into your repo

* Provide an entry script for CI that builds the container on-demand (and manages caching/cleanup) and then runs the tests/whatever inside that container

The point here is that docker/podman provide you with everything you need as long as you have full control. By using gitlab's default CI, you relinquish this control.

Re: Transitioning from Docker to Podman

#80

Post by qiqitori »

Assuming that it's Red Hat's fault that there is no el8 package for Docker, I think Red Hat is really shooting themselves in the foot by not supporting Docker in RHEL8. (You can still install the el7 version of Docker on el8 by performing an enable/disable/enable/disable/... module dance, but... why isn't there just an el8 version?)
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