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https://github.com/containers/quadlet


https://github.com/containers/quadlet

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README 

        
# Quadlet has been merged into [podman](https://github.com/containers/podman/tree/main/pkg/systemd/quadlet)



This repo is frozen.



# What is Quadlet



Quadlet is an opinionated tool for easily running podman system

containers under systemd in an optimal way.



# Why would I want that



Containers are often used in a cloud context, and they are then used

in combination with an orchestrator like Kubernetes. They are also

commonly used during development and testing to manually manage

containers on an ad-hoc basis.



However, there are also use cases where you want some kind of automatic

container management, but on a smaller, single-node scale, and often

more tightly integrated with the rest of the system. Typical examples

of this can be embedded or automotive use, where there is no system

administrator, or disconnected or EDGE servers.



The recommended way to do this is to use systemd to orchestrate the

containers, since this is an already running process manager, and

since podman containers are just child processes. There are many

documents that describe how to use podman with systemd directly, but

the end result are generally large, hard to maintain systemd config

files. And often the container setup isn't optimal.



With quadlet, you describe how to run a container in a format that is

very similar to regular systemd config files. From these actual

systemd configurations are automatically generated (using [systemd

generators](https://www.freedesktop.org/software/systemd/man/systemd.generator.html)).



The container descriptions focus on the relevant container details,

with no technical details about how the podman integration works. This

means they are easy to write, easy to maintain and integration can

automatically improve over time as new podman features become

available.



# A container example



Here is a minimal container config:



```

[Unit]

Description=A minimal container



[Container]

Image=centos

Exec=sleep 60



[Service]

Restart=always

```



This is very similar to a regular systemd service file, except for the

`[Container]` section. It will run `sleep 60` in a centos container, and

then exit only for systemd to restart it again.



If you put this in `/etc/containers/systemd/minimal.container` and

then run `systemctl daemon-reload` and `podman pull centos` you can

immediately start the container using `systemctl start

minimal.service` and watch the status:



```

# systemctl status minimal.service

● minimal.service - A minimal container

     Loaded: loaded (/etc/containers/systemd/minimal.container; generated)

     Active: active (running) since Thu 2021-09-23 13:05:33 CEST; 1s ago

    Process: 839846 ExecStartPre=rm -f /run/minimal.cid (code=exited, status=0/SUCCESS)

   Main PID: 839894 (conmon)

      Tasks: 4 (limit: 38375)

     Memory: 1.4M

        CPU: 193ms

     CGroup: /system.slice/minimal.service

             ├─container

             │ ├─839898 /dev/init -- sleep 60

             │ └─839943 /usr/bin/coreutils --coreutils-prog-shebang=sleep /usr/bin/sleep 60

             └─supervisor

               └─839894 /usr/bin/conmon ...

```



The generated service file is in

`/run/systemd/generator/minimal.service` for people interested in all

the technical details.



# Building quadlet



Quadlet builds using meson. You can build and install it with these

steps:



```

$ meson builddir  --prefix /usr

$ cd builddir

$ meson compile

$ meson install

```



This will install quadlet-generator in `/usr/lib/systemd/system-generators`, which will

read configuration files from `/etc/containers/systemd`.



# Where to go from here



Here are some further documentations:



 * [File formats](./docs/Fileformat.md)

 * [Container setup](./docs/ContainerSetup.md)



Quadlet also ships with some [example containers](./examples).