====== Systemd-resolved ======

----
Systemd-resolved provides resolver services for Domain Name System (DNS). 

===== Status =====
To check the DNS currently in use by systemd-resolved, run resolvectl status.
<code>
# resolvectl status
-----------------------------------------------
Global
       Protocols: +LLMNR +mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub

Link 2 (eth0)
    Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: fdaa:66:67:a::1
       DNS Servers: fdaa:66:67:a::1
-----------------------------------------------
</code>

===== Query =====
<code>
# resolvectl query www.oscardegroot.nl
-----------------------------------------------
www.oscardegroot.nl: 2001:1c00:2e16:720a:2ff:b1ff:feaa:1202 -- link: eth0
                     84.31.73.82               -- link: eth0
                     (oscardegroot.nl)

-- Information acquired via protocol DNS in 3.5ms.
-- Data is authenticated: no; Data was acquired via local or encrypted transport: no
-- Data from: network
-----------------------------------------------
</code> 

===== Configure =====
==== Supporting /etc/resolv.conf ====
To provide domain name resolution for software that reads /etc/resolv.conf directly, such as web browsers, systemd-resolved has four different modes for handling the file—stub, static, uplink and foreign. They are described in systemd-resolved(8). The recommended mode, is the stub mode which uses /run/systemd/resolve/stub-resolv.conf. /run/systemd/resolve/stub-resolv.conf contains the local stub 127.0.0.53 as the only DNS server and a list of search domains. This is the recommended mode of operation that propagates the systemd-resolved managed configuration to all clients. 
<code>
# ls -al resolv.conf 

    lrwxrwxrwx 1 root root 37 aug 13 07:27 resolv.conf -> /run/systemd/resolve/stub-resolv.conf

# cat /run/systemd/resolve/stub-resolv.conf

    nameserver 127.0.0.53
    options edns0 trust-ad
    search .
</code>

==== Automatically ====
systemd-resolved will work out of the box with a network manager using /etc/resolv.conf. No particular configuration is required since systemd-resolved will be detected by following the /etc/resolv.conf symlink.

==== Manually ====
The resolver can be configured by editing /etc/systemd/resolved.conf and/or drop-in .conf files in /etc/systemd/resolved.conf.d/



===== Links =====
  * https://wiki.archlinux.org/title/systemd-resolved