Linux/DNS

Ubuntu 18.04 show DNS settings

systemd-resolve --status

dig (testing)

• install

apt install dnsutils

• Basic query

dig google.com

• Query all record types

dig google.com ANY

• Query specific DNS server

dig google.de @8.8.8.8

• Reverse DNS lookup

dig -x 193.99.144.80

• Trace DNS path

dig google.com +trace

nslookup

nslookup google.com
nslookup -query=ANY google.com

DNS entry

$TTL 86400
@ IN SOA ns1.first-ns.de. postmaster.robot.first-ns.de. (
     2000091604  ; Serial
     14400       ; Refresh
     1800        ; Retry
     604800      ; Expire
     86400  )    ; Minimum

@           IN NS    ns1.first-ns.de.
@           IN NS    robotns2.second-ns.de.
@           IN NS    robotns3.second-ns.com.

localhost   IN A     127.0.0.1
@           IN A     1.2.3.4
www         IN A     2.3.4.5
www         IN AAAA  2001:db8::1
mail        IN A     2.3.4.5

loopback    IN CNAME localhost
pop         IN CNAME www
smtp        IN CNAME www
relay       IN CNAME www
imap        IN CNAME www
ftp    3600 IN CNAME ftp.anderedomain.de.

@           IN MX 10 mail

technik     IN A     5.6.7.8
technik     IN MX 10 technik

@           IN TXT   "v=spf1 mx -all"

DNS entry types

• ANY (all types)
• A (Host address)
• AAAA (IPv6 host address)
• ALIAS (Auto resolved alias)
• CNAME (Canonical name for an alias)
• MX (Mail eXchange)
• NS (Name Server)
• PTR (Pointer)
• SOA (Start Of Authority)

$TTL 86400
@ IN SOA ns1.first-ns.de. postmaster.robot.first-ns.de. (
2000091604  ; Serial
14400       ; Refresh
1800        ; Retry
604800      ; Expire
86400  )    ; Minimum

• SRV (location of service)
• TXT (Descriptive text)