The DNS server choice is saved in file /etc/pihole/setupVars.conf
Copy the contents of that file to another file (text editor perhaps), and see which DNS servers are in use.
Then make the changes on the web GUI, and reopen the setupVars.conf file and see if the file has changed. If the changes were not made, that's one problem. If the changes were made in the file, but not shown on the web interface, that is likely a different problem.
This file is copyright under the latest version of the EUPL.
Please see LICENSE file for your rights under this license.
############################################################################### #FILE AUTOMATICALLY POPULATED BY PI-HOLE INSTALL/UPDATE PROCEDURE.#
ANY CHANGES MADE TO THIS FILE AFTER INSTALL WILL BE LOST ON THE NEXT UPDATE
#IF YOU WISH TO CHANGE THE UPSTREAM SERVERS, CHANGE THEM IN:#
#/etc/pihole/setupVars.conf#
#ANY OTHER CHANGES SHOULD BE MADE IN A SEPARATE CONFIG FILE# #WITHIN /etc/dnsmasq.d/yourname.conf#
###############################################################################
ralf@ntp_server_1 ~ $ sudo service lighttpd status -l
[sudo] password for ralf:
● lighttpd.service - Lighttpd Daemon
Loaded: loaded (/lib/systemd/system/lighttpd.service; enabled)
Active: active (running) since Mi 2019-02-13 20:14:42 CET; 1 day 14h ago
Process: 604 ExecStartPre=/usr/sbin/lighttpd -t -f /etc/lighttpd/lighttpd.conf (code=exited, status=0/SUCCESS)
Main PID: 752 (lighttpd)
CGroup: /system.slice/lighttpd.service
├─752 /usr/sbin/lighttpd -D -f /etc/lighttpd/lighttpd.conf
├─770 /usr/bin/php-cgi
├─774 /usr/bin/php-cgi
├─775 /usr/bin/php-cgi
├─776 /usr/bin/php-cgi
└─777 /usr/bin/php-cgi
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: sudo: no tty present and no askpass program specified
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: We trust you have received the usual lecture from the local System
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: Administrator. It usually boils down to these three things:
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: #1) Respect the privacy of others.
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: #2) Think before you type.
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: #3) With great power comes great responsibility.
Feb 15 06:44:39 ntp_server_1 sudo[1611]: pam_unix(sudo:auth): conversation failed
Feb 15 06:44:39 ntp_server_1 sudo[1611]: pam_unix(sudo:auth): auth could not identify password for [www-data]
Feb 15 06:44:39 ntp_server_1 lighttpd[752]: sudo: no tty present and no askpass program specified
Feb 15 06:44:40 ntp_server_1 sudo[1611]: www-data : user NOT in sudoers ; TTY=unknown ; PWD=/var/www/html/admin ; USER=root ; COMMAND=/usr/local/bin/pih... no-dnssec
Hint: Some lines were ellipsized, use -l to show in full.