Linux for Noobs

Test connectivity between two computers

Code:
ping

Sample output:

Code:
~$ ping -c 5 1.1.1.1

PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data.

64 bytes from 1.1.1.1: icmp_seq=1 ttl=58 time=18.6 ms

64 bytes from 1.1.1.1: icmp_seq=2 ttl=58 time=18.4 ms

64 bytes from 1.1.1.1: icmp_seq=3 ttl=58 time=18.3 ms

64 bytes from 1.1.1.1: icmp_seq=4 ttl=58 time=18.4 ms

64 bytes from 1.1.1.1: icmp_seq=5 ttl=58 time=18.2 ms

--- 1.1.1.1 ping statistics ---

5 packets transmitted, 5 received, 0% packet loss, time 4005ms

rtt min/avg/max/mdev = 18.280/18.428/18.645/0.214 ms

Trace path to remote server

Code:
traceroute

Sample output:

Code:
~$ traceroute 1.1.1.1

traceroute to 1.1.1.1 (1.1.1.1), 30 hops max, 60 byte packets

 * * *

 45.63.113.1 (45.63.113.1)  4.686 ms  7.636 ms  10.529 ms

 * * *

 prs-b7-link.telia.net (62.115.58.17)  0.690 ms  0.678 ms  0.666 ms

 prs-bb4-link.telia.net (62.115.121.72)  0.617 ms prs-bb4-link.telia.net (213.155.134.228)  0.627 ms prs-bb4-link.telia.net (62.115.120.26)  0.615 ms

 prs-b8-link.telia.net (62.115.138.139)  1.191 ms prs-b8-link.telia.net (62.115.138.133)  1.181 ms  14.394 ms

 cloudflare-ic-154355-prs-b8.c.telia.net (80.239.194.118)  1.870 ms  1.865 ms  1.735 ms

 one.one.one.one (1.1.1.1)  0.807 ms  0.961 ms  0.969 ms

Perform DNS lookup and display the answer that is returned from the name server

Code:
dig

Sample output:

Code:
~$ dig linuxfornoobs.com

; <<>> DiG 9.10.3-P4-Ubuntu <<>> linuxfornoobs.com

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 330

;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

;; QUESTION SECTION:

;linuxfornoobs.com.             IN      A

;; ANSWER SECTION:

linuxfornoobs.com.      300     IN      A       104.27.187.153

linuxfornoobs.com.      300     IN      A       104.27.186.153

;; Query time: 19 msec

;; SERVER: 108.61.10.10#53(108.61.10.10)

;; WHEN: Tue Feb 05 11:23:56 CET 2019

;; MSG SIZE  rcvd: 78

Alternative #1:

Code:
nslookup

Sample output:

Code:
~$ nslookup linuxfornoobs.com

Server:         10.10.10.10

Address:        10.10.10.10#53

Non-authoritative answer:

Name:   linuxfornoobs.com

Address: 104.27.186.153

Name:   linuxfornoobs.com

Address: 104.27.187.153

Name:   linuxfornoobs.com

Address: 2606:4700:30::681b:ba99

Name:   linuxfornoobs.com

Address: 2606:4700:30::681b:bb99

Alternative #2:

Code:
host

Sample output:

Code:
~$ host linuxfornoobs.com

linuxfornoobs.com has address 104.27.187.153

linuxfornoobs.com has address 104.27.186.153

linuxfornoobs.com has IPv6 address 2606:4700:30::681b:ba99

linuxfornoobs.com has IPv6 address 2606:4700:30::681b:bb99

linuxfornoobs.com mail is handled by 10 c2b0268c838472d1.mx1.emailprofi.seznam.cz.

linuxfornoobs.com mail is handled by 20 c2b0268c838472d1.mx2.emailprofi.seznam.cz.

Active Internet connections (servers and established)

Code:
ss -neopa

Alternative (deprecated):

Code:
netstat -neopa

Active Internet connections (only servers)

Code:
ss -tulpn

Alternative (deprecated):

Code:
netstat -tulpn

Show routing table

Code:
ip r

Alternatives (deprecated):

Code:
netstat -rnv

route

Display ethernet card settings such as auto-negotiation, port speed, duplex mode, and Wake-on-LAN

Code:
ethtool

Sample output:

Code:
~$ sudo ethtool ens32

Settings for ens32:

        Supported ports: [ TP ]

        Supported link modes:   10baseT/Half 10baseT/Full

                                100baseT/Half 100baseT/Full

                                1000baseT/Full

        Supported pause frame use: No

        Supports auto-negotiation: Yes

        Supported FEC modes: Not reported

        Advertised link modes:  10baseT/Half 10baseT/Full

                                100baseT/Half 100baseT/Full

                                1000baseT/Full

        Advertised pause frame use: No

        Advertised auto-negotiation: Yes

        Advertised FEC modes: Not reported

        Speed: 1000Mb/s

        Duplex: Full

        Port: Twisted Pair

        PHYAD: 0

        Transceiver: internal

        Auto-negotiation: on

        MDI-X: off (auto)

        Supports Wake-on: d

        Wake-on: d

        Current message level: 0x00000007 (7)

                               drv probe link

        Link detected: yes

paia