netdev - Re: [iproute2 00/22] Support for stateless configuration (read from /etc and /usr)

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Message-ID: <6041446f-ad4f-1b5a-9b7e-b496de080468@svario.it>
Date: Thu, 20 Jul 2023 08:05:17 +0200
From: Gioele Barabucci <gioele@...rio.it>
To: Stephen Hemminger <stephen@...workplumber.org>
Cc: netdev@...r.kernel.org
Subject: Re: [iproute2 00/22] Support for stateless configuration (read from
 /etc and /usr)

On 19/07/23 23:36, Stephen Hemminger wrote:
> On Wed, 19 Jul 2023 20:50:44 +0200
> Gioele Barabucci <gioele@...rio.it> wrote:
> 
>> this patch series adds support for the so called "stateless" configuration
>> pattern, i.e. reading the default configuration from /usr while allowing
>> overriding it in /etc, giving system administrators a way to define local
>> configuration without changing any distro-provided files.
>>
>> In practice this means that each configuration file FOO is loaded
>> from /usr/lib/iproute2/FOO unless /etc/iproute2/FOO exists.
> 
> I don't understand the motivation for the change.

The main, but not the only, motivation for stateless systems is explained in

https://clearlinux.org/features/stateless
https://fedoraproject.org/wiki/StatelessLinux
https://summit.debconf.org/debconf15/meeting/276/stateless-cloud-friendly-debian/

In a nutshell: to better support factory resets, shared read-only base 
systems, containers & Co, all software should work even without /etc.

A nice side effect of adopting stateless-style configuration (read from 
/etc, fallback to /usr) is that it allows for distro-provided files to 
be strictly read-only, avoiding a bunch of common failures during 
updates and upgrades (Debian spends a huge amount of resources to 
correctly handle these so called "conffiles". The fewer, the better.)

> Is /etc going away in some future version of systemd?
This is unrelated to systemd, although systemd is probably the most well 
known software that uses this pattern.

> Perhaps just using an an environment variable instead of hard coding
> /etc/iproute2 directory.

Build-time or run-time env variable?

I'd say that run-time env variables (a là XDG Base Directory) are kind 
of hard to deal with in a command like `ip` that is often invoked via 
`sudo` (that filters and changes env in complex ways).

BTW, I strongly suggest to just go with this common pattern that is now 
known to all sysadmins instead of inventing an ad-hoc way to move the 
default configuration away from /etc.

> I do like the conslidation of the initialize_dir code though.

Thanks. :)

Regards,

-- 
Gioele Barabucci