> (how many people knew this was a default before now?) Pretty much everyone who...

falcolas · on July 2, 2020

Did you know that there are at least four different file locations that resolvers can be set in for systemd-resolved?

The defaults being in a commented-out section in one of these four locations (and in a file whose name does not match the linux standard of resolv.conf) is, frankly, not a big help in identifying what's really being used.

https://jlk.fjfi.cvut.cz/arch/manpages/man/systemd-resolved....

JdeBP · on July 2, 2020

Actually, it's five, or even six. systemd doco is bad at including /usr/local/ .

You are pointing to the wrong manual page, incidentally. It's resolved.conf(5). This fails to list /usr/local/lib/systemd/resolved.conf.d/ , which is scanned before /usr/lib/systemd/resolved.conf.d/ (and if configured /lib/systemd/resolved.conf.d/).

megous · on July 2, 2020

How do any of those 4 resolv.conf location variants change where the compiled-in fallback is configured/visible?

If user wants to know what's really being used for name resolution he should go to /etc/nsswtich.conf and /etc/hosts and /etc/resolv.conf as usual.

JdeBP · on July 2, 2020

If systemd-resolved is actually being used, /etc/resolv.conf will list only 127.0.0.53, and to find out what systemd-resolved itself is using one has to visit the resolved.conf configuration files, which is what falcolas is apparently talking about.

But then if one is using, say, dnscache or dnsmasq or MaraDNS or BIND or PowerDNS or any other such software, one has to do the same thing. /etc/resolv.conf will list simply 127.0.0.1 or some such, and one has to go further to the configuration files of those softwares to find out what they are using for resolution/forwarding.

DNS softwares having their own configuration files is normal. falcolas is apparently getting at the fact that systemd-resolved uses the same style of configuration as the other systemd programs do: files and drop-in directories in /etc/systemd, /run/systemd, /usr/local/lib/systemd, /usr/lib/systemd, and (if configured) /lib/systemd, meaning that one has to read all of this together.

megous · on July 2, 2020

It would be clearer if he linked to https://jlk.fjfi.cvut.cz/arch/manpages/man/resolved.conf.5.e... then.

Anyway, in default config, there will be only the file I mentioned. And whole this issue is about default configuration.

JdeBP · on July 2, 2020

Actually, no. The headlined issue is about what the fallback is when there is no file, or a file that doesn't specify a setting.

megous · on July 3, 2020

There's always /etc/systemd/resolved.conf in default installation/build.

JdeBP · on July 5, 2020

... which does not specify a setting. As falcolas explained at the start. Have you caught up now?

djsumdog · on July 2, 2020

Wow. I never realized there was a DNS server listening at 127.0.0.53 on systemd based distros.

creeble · on July 2, 2020

Just try using a system on a "captive portal" wifi connection. You will soon learn "apt purge systemd-resolvd".

munchbunny · on July 2, 2020

Pretty much everyone who ever opened /etc/systemd/resolved.conf

That's a vanishingly small percentage of people who use systemd.

megous · on July 2, 2020

Perhaps, but still larger than the set of people who compile their own systemd builds.

Also it's the answer to the question. The defaults are visible in config files as commented out lines. No need to check build scripts, etc.

hedora · on July 2, 2020

If you are correct, Poettering doesn’t understand how to configure the last resort fallback.

He says the easiest way is to recompile systemd from source.

Presumably he knows more about systemd then the average Linux user.

megous · on July 2, 2020

You're assuming a lot of things. That I'm an average user (I'm not) and that thing about Poettering.