[Info-vax] systemd (was Re: openvms and xterm)

[Lawrence D'Oliveiro]

On Mon, 22 Apr 2024 09:26:50 +1000, motk wrote:

> Those are entirely optional, but very handy for embedded/cloud image/iot 
> stuff, where you don't want to pull in an entire distros worth of stuff.

Just an example of the many modular parts of systemd:

I encountered systemd-networkd for the first time the other day, while
setting up a BigBlueButton server for a customer. The install script
recommends you start with a fresh Ubuntu Server install. But there
seems to be something buggy about the Ubuntu Server installer: I kept
trying to put in manual parameters for a network interface (address,
router, DNS), but they wouldn’t stick.

Finally I gave up on manual network configuration, and left it to
default to DHCP for the installation, figuring I’d fix it up later.

So I went in afterwards, looking for the traditional Debian
/etc/network/interfaces file, only to discover it didn’t exist.
Instead, you created .network files, one for each interface. So I read
the man page on how to do that. I discovered the autogenerated one in
/run/systemd/network that was using DHCP, and the docs said that if I
created a file with the same name in /etc/systemd/network, it would
override the former.

So I did, and it worked.

Another nice thing I found is, I could manually try different
temporary network settings without updating those config files, and it
would leave my fiddling alone. In order to (re)apply the configuration
settings and wipe out my temporary changes, I had to explicitly say
“systemctl restart systemd-networkd.service”. Compare this with
NetworkManager, where if you try manually fiddling things, it will at
some point automatically, and unpredictably, decide to override your
changes with its configured settings.