Name resolution issues causing inability to claim server - Arch Linux

Plex Media Server Desktops & Laptops
5

My solution (fixed dig and plex name resolution issues):

Comment out all lines of /etc/systemd/resolved.conf.
Make /etc/resolv.conf a symlink to /run/systemd/resolved/resolv.conf

sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf

where /run/systemd/resolve/resolv.conf contains the contents below.

# Resolver configuration file.
# See resolv.conf(5) for details.
nameserver 1.1.1.1 8.8.8.8

This solution was not necessary before v1.23.

$ /usr/lib/plexmediaserver/Plex\ Media\ Server --version
v1.23.2.4656-85f0adf5b

Failed attempted solutions:
This forum post reports the same symptoms, and gave me many ideas for solutions.

  • Adding Linux user plex to systemd-resolve and systemd-network Linux user groups
  • Setting Domains=plex.tv in /etc/systemd/resolved.conf
  • Booting with kernel parameter ipv6.disable=1 to see if this was IPv6 related (it wasn’t).
  • Setting ISP-provided DNS servers as my DNS= parameter in /etc/systemd/resolved.conf instead of Cloudflare (1.1.1.1) or Google (8.8.8.8)
  • Trying enabling and disabling DNS settings like LLMNR, DNSSEC, and ResolveUnicastSingleLabel in /etc/systemd/resolved.conf

Notes:
While I would not describe my Arch Linux system as having global DNS issues, (curl and ping work), the post linked at the top of this reply showed me the value of dig as another DNS resolution testing tool that can reveal extra DNS issues (comes in the bind-tools Arch Linux package). Before implementing the fix at the bottom, dig never returned anything for any domain unless I provided a DNS for it to use on the command line, which told me it did not know where it could find a list of DNS servers to use.

dig plex.tv AAAA
; <<>> DiG 9.16.16 <<>> plex.tv AAAA
;; global options: +cmd
;; connection timed out; no servers could be reached

and

dig @1.1.1.1 plex.tv AAAA
; <<>> DiG 9.16.16 <<>> @1.1.1.1 plex.tv AAAA
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 11060
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;plex.tv.                       IN      AAAA

;; AUTHORITY SECTION:
plex.tv.                2486    IN      SOA     jeremy.ns.cloudflare.com. dns.cloudflare.com. 2037520463 10000 2400 604800 3600

;; Query time: 6 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Sun Jun 13 15:23:37 EDT 2021
;; MSG SIZE  rcvd: 100

so it became apparent that some apps on Arch Linux (and maybe linux in general, I don’t know) can check in different places for which DNS servers to use (some check /etc/systemd/resolved.conf, others (plex and dig) seem to only check /etc/resolv.conf).