maintaining accurate time
it’s ok to have the wrong time as long as everyone has the wrong time
timedatectl : see system time
user@host ~ > timedatectl Local time: Tue 2019-12-10 17:11:32 CST Universal time: Tue 2019-12-10 23:11:32 UTC RTC time: Tue 2019-12-10 23:11:32 Time zone: America/Chicago (CST, -0600) NTP enabled: yes NTP synchronized: yes RTC in local TZ: no DST active: no Last DST change: DST ended at Sun 2019-11-03 01:59:59 CDT Sun 2019-11-03 01:00:00 CST Next DST change: DST begins (the clock jumps one hour forward) at Sun 2020-03-08 01:59:59 CST Sun 2020-03-08 03:00:00 CDT
timedatectl set-timezone America/New_York
timedatectl set-ntp true
/etc/chrony.conf : config file for chronyd
chapter 12 - managing networking - managing networking concepts
- ethernet :
en - wireless :
wl - WWAN :
ww
eno1 : on-board ethernet interface with an index number of 1
ens3 : hot-plug slot ethernet device in slot 3
ip addresses
- ip address itself
- subnet mask
- host portion
- network portion
- facilitates routing
255.255.255.0 is /24 or 24 bits
octets and bits
IPv4 Routing
192.168.5.254
- 192.168.5.3
- 192.168.5.1
sub elements can communicate without routing
but if need internet, need routing
192.168.5.254 is the route gateway
sends to DNS server for further routing, 172.17.0.0/16
routing is required when devices are on different networks
IPv6 128 bits, 8 groups of 4 hexidecimal nibbles
link-local address:
- fe80::/10
- not routable
- unique
- something mac address with funky mathematics
to get routable
- static assignments
- DHCP
- SLAAC
- provide routable IPv6 IP automatically
ip a : not the same as IPA
ping ping6
cat /etc/hosts : dns names and ip addresses
head /etc/services : commonly used services
cat /etc/resolv.conf : DNS service that you make use of
validating network configuration
ip address show
ip a s
ip link show
discouraged from using ifconfig, ifup, ifdown, deprecated
traceroute