Resolve:

systemd-resolve -t MX gmail.com   #show mail server

systemd-resolve -t SOA gmail.com   #show SOA .     Start Of Authority (More administrative information)   URL

systemd-resolve 85.214.157.7        #Get domain name

nslookup domain.ir [#Finding The IP Address of an Host from default dns server]

nslookup domain.ir 8.8.8.8[#Finding The IP Address of an Host From non default dns server]

nslookup -querytype=mx domain.ir[ #Find Mail Servers for a Domain]

nslookup -query=mx domain.ir [#Find Mail Servers]

nslookup -query=ns domain.ir [ #Find NameServers]

nslookup -query=soa domain.ir [ #display the SOA record (information about the domain]

nslookup -query=any domain.ir [ #display all the available DNS records]

host -la domain.com [Show all record with Information]

dig Domain.it axfr [Show all record with Information]

systemd-resolve --statistics          #informations

Flush the DNS Cache   URL

Method 1: Using systemd-resolve to flush DNS-Cache

sudo systemd-resolve --flush-caches

sudo systemd-resolve --statistics

Method 2: Using dns-clean to flush DNS-Cache

sudo /etc/init.d/dns-clean start

Resolve.conf

Install:

sudo apt install resolvconf

For fix and NotChange file:

vim  /etc/NetworkManager/NetworkManager.conf

#Add below to main area :

dns=none