Configure Networking, Time Services

Question 1

What is the command to show all network interfaces?

Answer 1

ip addr

Question 2

What is the command to show a specific network interface?

Answer 2

ip addr show {ifname}

Question 3

What is the command to trace the route of a packet?

Answer 3

traceroute

tracepath

Question 4

What is the command to show listening ports and established connections?

Answer 4

ss

netstat *older

Question 5

How do you show statistics on a network interface?

Answer 5

ip -s link show {ifname}

Question 6

Where are networking devices located on the system?

Answer 6

/sys/class/net

Question 7

How do you see the state of network devices?

Answer 7

nmcli dev status

Question 8

What is the NetworkManager command to show network configurations?

Answer 8

nmcli con show

Question 9

What is the NetworkManager command to add a DHCP connection that autoconnects on reboot?

Answer 9

nmcli con add con-name {name} autoconnect yes type ethernet ifname {ifname}

Question 10

Where are NetworkManager configurations located?

Answer 10

/etc/sysconfig/network-scripts/

*ifcfg- files are config files for network interfaces

Question 11

What is the NetworkManager command to add a static IP connection that autoconnects on reboot?

Answer 11

nmcli con add con-name {name} autoconnect yes type ethernet ifname {ifname} ip4 {ip} gw4 {gateway}

Question 12

What is the NetworkManager command to bring down a network connection?

Answer 12

nmcli con down {name}

Question 13

What is the NetworkManager command to bring up a network connection?

Answer 13

nmcli con up {name}

Question 14

How do you modify a connection using NetworkManager?

Answer 14

nmcli con mod {name}

*can also edit config files in /etc/sysconfig/network-scripts

Question 15

How do you delete a NetworkManager connection?

Answer 15

nmcli con del {name}

Question 16

Where are DNS servers located?

Answer 16

/etc/resolv.conf

nameserver {server1} {server2} {etc}

Question 17

Where is the hosts file located?

Answer 17

/etc/hosts

*resolves names to ip manually

Question 18

How can you make either the /etc/hosts file or /etc/resolv.conf authoritative?

Answer 18

Edit /etc/nsswitch.conf
hosts: files dns myhostname
Order in which names will be resolved

Question 19

Where is the hostname of the system stored?

Answer 19

/etc/hostname

Question 20

What is the command to change hostname?

Answer 20

hostname *not persistent

hostnamectl set-hostname *persistent

Question 21

In /etc/resolve.conf what does search followed by a domain name do?

Answer 21

i.e search domain.com
When resolving a hostname the FQDN does not have to be specified for all search entries. The domain will be automatically appended.

Question 22

How would you use NetworkManager to add a network interface specific DNS address?

Answer 22

nmcli con mod {name} ipv4.dns {ip}
+ipv4.dns {ip} *add additional
-ipv4.dns {ip} *remove nameserver

Question 23

How do you resolve a hostname strictly internally?

Answer 23

getent host {name}

Question 24

How do you get information about system time?

Answer 24

timedatectl

date

Question 25

How do you set the timezone?

Answer 25

timezonectl set-timezone

Question 26

How do you enable/disable NTP?

Answer 26

timezonectl set-ntp true

timezonectl set-ntp false

Question 27

How do you set the time?

Answer 27

timedatectl set-time {time}

*first disable NTP

Question 28

What is the service that configures NTP?

Answer 28

chronyd

ntpd *older

Question 29

How do you see which servers are being used to sync by NTP?

Answer 29

chronyc sources -v

located at /etc/chrony.conf

Question 30

How do you see advances NTP information?

Answer 30

chronyc tracking
*shows information such as update interval
speeds/slows system clock incrementally to correct time to avoid breaking applications