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docs: document new sd_notify() extensions

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Lennart Poettering
2024-03-14 17:24:24 +01:00
parent e6ceea090a
commit 1e785c50c9
3 changed files with 116 additions and 22 deletions
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docs/CONTAINER_INTERFACE.md
+15 -8
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@@ -165,10 +165,15 @@ manager, please consider supporting the following interfaces.
issuing `journalctl -m`. The container machine ID can be determined from
`/etc/machine-id` in the container.
3. If the container manager wants to cleanly shutdown the container, it might
3. If the container manager wants to cleanly shut down the container, it might
be a good idea to send `SIGRTMIN+3` to its init process. systemd will then
do a clean shutdown. Note however, that since only systemd understands
`SIGRTMIN+3` like this, this might confuse other init systems.
`SIGRTMIN+3` like this, this might confuse other init systems. A container
manager may implement the `$NOTIFY_SOCKET` protocol mentioned below in which
case it will receive a notification message `X_SYSTEMD_SIGNALS_LEVEL=2` that
indicates if and when these additional signal handlers are installed. If
these signals are sent to the container's PID 1 before this notification
message is sent they might not be handled correctly yet.
4. To support [Socket Activated
Containers](https://0pointer.de/blog/projects/socket-activated-containers.html)
@@ -190,12 +195,14 @@ manager, please consider supporting the following interfaces.
unit they created for their container. That's private property of systemd,
and no other code should modify it.
6. systemd running inside the container can report when boot-up is complete
using the usual `sd_notify()` protocol that is also used when a service
wants to tell the service manager about readiness. A container manager can
set the `$NOTIFY_SOCKET` environment variable to a suitable socket path to
make use of this functionality. (Also see information about
`/run/host/notify` below.)
6. systemd running inside the container can report when boot-up is complete,
boot progress and functionality as well as various other bits of system
information using the `sd_notify()` protocol that is also used when a
service wants to tell the service manager about readiness. A container
manager can set the `$NOTIFY_SOCKET` environment variable to a suitable
socket path to make use of this functionality. (Also see information about
`/run/host/notify` below, as well as the Readiness Protocol section on
[systemd(1)](https://www.freedesktop.org/software/systemd/man/latest/systemd.html)
## Networking