Re: [PATCH v2 2/3] host/rootfs: Switch to systemd-udevd

[Alyssa Ross <hi@alyssa.is>]

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Demi Marie Obenour <demiobenour@gmail.com> writes:

> On 9/25/25 06:53, Alyssa Ross wrote:
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>> 
>>> diff --git a/host/rootfs/image/etc/s6-rc/kvm/up b/host/rootfs/image/etc/s6-rc/kvm/up
>>> index c02e3f90245e005b98b4de8245a1863fb49c1158..a8436de58580f2a2a6f42bb69418a319f967df47 100644
>>> --- a/host/rootfs/image/etc/s6-rc/kvm/up
>>> +++ b/host/rootfs/image/etc/s6-rc/kvm/up
>>> @@ -1,4 +1,3 @@
>>>  # SPDX-License-Identifier: EUPL-1.2+
>>> -# SPDX-FileCopyrightText: 2023 Alyssa Ross <hi@alyssa.is>
>>> -
>>> -/etc/mdev/wait kvm
>>> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
>>> +udevadm wait /dev/kvm
>> 
>> Any reason now not to just inline this into the services that need to wait?
>
> Avoiding redundant calls I guess?  I'm not
> sure how expensive 'udevadm wait' is.

Then let's drop the service and see if it becomes a problem.  I suspect
it won't.

>>> diff --git a/host/rootfs/image/etc/s6-rc/systemd-udevd/run b/host/rootfs/image/etc/s6-rc/systemd-udevd/run
>>> new file mode 100644
>>> index 0000000000000000000000000000000000000000..2501680b69eb0060b651146dffb6b3a99640c6fb
>>> --- /dev/null
>>> +++ b/host/rootfs/image/etc/s6-rc/systemd-udevd/run
>>> @@ -0,0 +1,11 @@
>>> +#!/bin/execlineb -P
>>> +# SPDX-License-Identifier: EUPL-1.2+
>>> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com>
>>> +if { rm -f /run/sd-notify-wrapper/systemd-udevd }
>>> +background {
>>> +   s6-ipcserver-socketbinder -b0 -m -a 0600 /run/sd-notify-wrapper/systemd-udevd
>>> +   fdmove 1 3
>>> +   sd-notify-adapter
>>> +}
>>> +export NOTIFY_SOCKET /run/sd-notify-wrapper/systemd-udevd
>>> +exec -a systemd-udevd udevadm
>> 
>> How does systemd expect this to normally work?
>
> /usr/lib/systemd/systemd-udevd is a symlink to ../../bin/udevadm

Ah, and you had the problem that currently it's hard to install things
other than kernel modules to /usr/lib.  We can probably fix that.

>>> diff --git a/host/rootfs/image/etc/s6-rc/vm-env/contents b/host/rootfs/image/etc/s6-rc/vm-env/contents
>>> index 580795b1b02bb7a8dff7f872723c678141d4bb70..ed8b5c410adfc17f5bbc33932ac79d97bd7b3115 100644
>>> --- a/host/rootfs/image/etc/s6-rc/vm-env/contents
>>> +++ b/host/rootfs/image/etc/s6-rc/vm-env/contents
>>> @@ -2,4 +2,5 @@
>>>  # SPDX-FileCopyrightText: 2021 Alyssa Ross <hi@alyssa.is>
>>>  #
>>>  static-nodes
>>> +systemd-udevd-coldplug
>>>  weston
>> 
>> Shouldn't static-nodes be removed here as well, and the static-nodes
>> files deleted?
>
> Nope.  systemd-udevd doesn't create them.  However,
> one can use kmod and systemd-tmpfiles to do that.
>
> systemd-tmpfiles actually has no dependency on PID 1
> *at all*, so we can use it as much as we want.

Oh, I see, okay.  That's a separate series then. :)

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