Bug#931130: Document that local configuration for dummy and bonding modules are getting overwritten by systemd

[Justin B Rye]

Michael Biebl wrote:
> Am 29.06.19 um 15:09 schrieb Justin B Rye:
>> +      configure a machine as a router, may encounter problems upgrading to buster.
>> +      New versions of <systemitem role="package">udev</systemitem> install a
> 
> That modprobe config file is shipped by the systemd package, not by udev.

Ah, thanks.
 
>> A file in
>> +      <filename>/lib/modprobe.d</filename> can be overridden by one with the
>> +      same name under <filename>/etc/modprobe.d</filename>, but the names are
>> +      processed in alphabetical order, so
> 
> That sentence is a bit confusing: files with the same name are
> overridden. period. there is no but.

If there wasn't a "but", people wouldn't have been caught out!  It's
true that if you create a file in /etc then you don't need to worry
about the one it masks in /lib, but you do still need to worry about
others that might turn up in /lib with names that sort later.

> Are you trying to say that files can be overridden as a whole but
> usually its better to only override specific settings in a local
> configuration file which doesn not have the same name?

No, I *could* have added a paragraph explaining the drawbacks of using
the filename /etc/modprobe.d/systemd.conf, but it seemed simpler just
to not mention the suboptimal solution.  After all, who knows what
might turn up in bullseye's /etc/modprobe.d/udev.conf?

> (which is indeed a useful recommendation because future updates of
> systemd.conf might be missed if you name the file
> /etc/modprobe.d/systemd.conf).

The simplest way of looking at this bug is that the old approach
(as recommended in legacy HOWTOs) of using filenames like
"/etc/modprobe.d/dummy.conf" needs to be updated to using something
like "/etc/modprobe.d/zz-local.conf".  My explanation covers things in
what I hoped was just enough detail to make it clear why that change
is needed.


I've stared at it quite a bit and can't find a clearer way of saying
it.  Here's a patch with just the s/udev/systemd/ change; I'll go for
a walk and then try looking at it again.
-- 
JBR	with qualifications in linguistics, experience as a Debian
	sysadmin, and probably no clue about this particular package
-------------- next part --------------
A non-text attachment was scrubbed...
Name: dummy-module-config3.diff
Type: text/x-diff
Size: 2815 bytes
Desc: not available
URL: <http://alioth-lists.debian.net/pipermail/pkg-systemd-maintainers/attachments/20190629/532acbb1/attachment.diff>