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| -rw-r--r-- | docs/tutorials/socket_activation.md | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/docs/tutorials/socket_activation.md b/docs/tutorials/socket_activation.md index 9b4b02b81..f4ad5aefd 100644 --- a/docs/tutorials/socket_activation.md +++ b/docs/tutorials/socket_activation.md @@ -19,7 +19,7 @@ The architecture looks like this ``` mermaid stateDiagram-v2 - [*] --> systemd: client connects + [*] --> systemd: first client connects systemd --> podman: socket inherited via fork/exec ``` @@ -55,6 +55,9 @@ $ export DOCKER_HOST=unix://$XDG_RUNTIME_DIR/podman/podman.sock $ docker-compose up ``` +When __docker-compose__ or any other client connects to the UNIX socket `$XDG_RUNTIME_DIR/podman/podman.sock`, +the service _podman.service_ is started. See its definition in the file _/usr/lib/systemd/user/podman.service_. + ## Socket activation of containers Since version 3.4.0 Podman supports socket activation of containers, i.e., passing @@ -65,7 +68,7 @@ as can be seen in the following diagram: ``` mermaid stateDiagram-v2 - [*] --> systemd: client connects + [*] --> systemd: first client connects systemd --> podman: socket inherited via fork/exec state "OCI runtime" as s2 podman --> conmon: socket inherited via double fork/exec @@ -207,6 +210,18 @@ container then runs with less privileges. When using rootless Podman, network traffic is normally passed through slirp4netns. This comes with a performance penalty. Fortunately, communication over the socket-activated socket does not pass through slirp4netns so it has the same performance characteristics as the normal network on the host. -Note, there is a delay when the first connection is made because the container needs to + +### Starting a socket-activated service + +There is a delay when the first connection is made because the container needs to start up. To minimize this delay, consider passing __--pull=never__ to `podman run` and instead -pull the container image beforehand. +pull the container image beforehand. Instead of waiting for the start of the service to be triggered by the +first client connecting to it, the service can also be explicitly started (`systemctl --user start echo.service`). + +### Stopping a socket-activated service + +Some services run a command (configured by the systemd directive __ExecStart__) that exits after some time of inactivity. +Depending on the restart configuration for the service +(systemd directive [__Restart__](https://www.freedesktop.org/software/systemd/man/systemd.service.html#Restart=)), +it may then be stopped. An example of this is _podman.service_ that stops after some time of inactivity. +The service will be started again when the next client connects to the socket. |