- Networking
See p4 of Bite-Sized Networking for more info.
The command is a DNS lookup tool. It can be installed using the dnsutils library on Ubuntu. This is already added to the accompanying Dockerfile.
Some things to try...
$ dig txidigital.com
# will output the DNS A record information for txidigital.com
$ dig cname txidigital.com
# will output the DNS CNAME record information
$ dig mx txidigital.com
# will output the MX records information
$ dig +short txidigital.com
# will show a short version of the output based on the type of record requestedHat tip to @phoolish for sharing https://www.dns.toys/ which provides a bunch of fun things you can do with dig.
$ dig +short aberdeen/gb.time @dns.toys
"Aberdeen (Europe/London, GB)" "Tue, 05 Jul 2022 19:56:31 +0100"
$ dig +short aberdeen/gb.weather @dns.toys
"Aberdeen (GB)" "13.20C (55.76F)" "75.60% hu." "cloudy" "20:00, Tue"
"Aberdeen (GB)" "12.70C (54.86F)" "80.20% hu." "cloudy" "22:00, Tue"
"Aberdeen (GB)" "12.90C (55.22F)" "79.90% hu." "cloudy" "00:00, Wed"
"Aberdeen (GB)" "12.40C (54.32F)" "85.60% hu." "rain" "02:00, Wed"
"Aberdeen (GB)" "12.40C (54.32F)" "91.30% hu." "cloudy" "04:00, Wed"See p5 of Bite-Sized Networking for more info.
ping let's you "ping" a server to make sure that you can get a connection to it. You can also check the latency of that connection (i.e. how long it takes to get there and back again).
ping works by sending an ICMP packet and waiting for a reply
From https://www.cloudflare.com/learning/ddos/glossary/internet-control-message-protocol-icmp/
The Internet Control Message Protocol (ICMP) is a network layer protocol used by network devices to diagnose network communication issues. ICMP is mainly used to determine whether or not data is reaching its intended destination in a timely manner.
$ ping txidigital.com
PING txidigital.com (69.167.171.6) 56(84) bytes of data.
64 bytes from 69.167.171.6: icmp_seq=1 ttl=37 time=116 ms
64 bytes from 69.167.171.6: icmp_seq=2 ttl=37 time=114 ms
64 bytes from 69.167.171.6: icmp_seq=3 ttl=37 time=117 ms
... # will keep running until you Ctrl-C
$ ping -c3 txidigital.com
PING txidigital.com (69.167.171.6) 56(84) bytes of data.
64 bytes from 69.167.171.6: icmp_seq=1 ttl=37 time=116 ms
64 bytes from 69.167.171.6: icmp_seq=2 ttl=37 time=114 ms
64 bytes from 69.167.171.6: icmp_seq=3 ttl=37 time=117 ms
# with -c<n> it will only run n timesNote that the latency is pretty slow for me time=116ms. This is because I'm based in the UK. We get a better latency running from a US-based server.
$ ping -c3 txidigital.com
PING txidigital.com (69.167.171.6) 56(84) bytes of data.
64 bytes from 69.167.171.6: icmp_seq=1 ttl=47 time=24.8 ms
64 bytes from 69.167.171.6: icmp_seq=2 ttl=47 time=24.8 ms
64 bytes from 69.167.171.6: icmp_seq=3 ttl=47 time=24.7 ms
--- txidigital.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2027ms
rtt min/avg/max/mdev = 24.786/24.833/24.896/0.046 msSee p5 of Bite-Sized Networking for more info.
When we get to this one we should check out https://smallstep.com/blog/if-openssl-were-a-gui/. Thanks to @phoolish for sharing.
This is one I use a fair bit because I can never remember what I've left running somewhere! I'll update this section more when I come to it and explore some more, but for now this is how I use it.
$ ss -lnt
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
LISTEN 0 4096 127.0.0.1:6443 0.0.0.0:*
LISTEN 0 511 127.0.0.1:43651 0.0.0.0:*This shows the port number (-n) for all listening (-l) connections on TCP (-t). I use it to find things like web servers, database servers and the like.