108.1 Maintain System Time

What two options of hwclock are used to set the hardware clock to a specific time?

--set --date e.g. --set --date="9/16/11 08:00:00"

The ______ option(s) of hwclock reads the current time from the hardware clock and displays it

-r or --show

Which option(s) of hwclock specifies that the hardware clock is configured to use either UTC or local time?

-utc --localtime

What config files are these two lines from and what is their purpose? server 127.127.1.0 # local clock (LCL) fudge 127.127.1.0 stratum 10 # LCL is unsynchronized

/etc/ntp.conf They are directives if the time server is not available to use the local clock.

Name three key functions of the hwclock command

1. Display current time 2. Set the hardware clock time 3. Synchronize the hardware clock to the system clock and vice versa.

The NTP protocol operates over IP port _____

123

At what difference in time between an NTP server and a system will the ntpd consider the time difference to be "insane" and fail to adjust it?

17 minutes.

What is a stratum as it pertains to NTP, and what role does it play in NTP?

A stratum is a tier or hierarchy of NTP servers, each of which pass their time to the following tier in the hierarchy, Stratum 1 being the first. They get their time from a reference time source such as the Naval atomic clock. Stratum 1 (gets time from Naval atomic clock) Stratum 2 (gets time from Stratum 1) Stratum 3 (gets time from Stratum 2) Stratum n (depth of 256 strata)

What is the function of the ntpdate function?

Eliminate "insane" time issues by performing an initial sync to get time close before you start ntpd *ntpd must be stopped before you run this command*

One of the best ways to keep local time synchronized on a regular basis is to use the ________________ (NTP)

Network Time Protocol

The -w option of hwclock can be used for ________________. What other option syntax accomplishes the same?

Synchronize the hardware clock to the current time of the system time. --systohc

The -s option of hwclock can be used for ________________. What other option syntax accomplishes the same?

Synchronize the system time to the current time of the hardware clock. --hctosys

TRUE or FALSE: The hardware clock and system time may not be the same

TRUE

Which command can be used to synchronize time on the local system with the time on a time server over the network?

netdate

What is the main difference between syncing your time through a command like netdate vs. NTP?

netdate is an immediate, abrubt adjustment of time, whereas NTP adjusts gradually over the course of some time.

NTP uses the ________ daemon to synchronize time with another NTP provider.

ntpd

What command queries the status of the ntpd daemon and displays info about the time providers it is sourcing from?

ntpq -p

To ensure no one server is overloaded with time sync requests, ______________ use DNS round robin to make a random selection from time providers who have volunteered.

pool.ntp.org (NTP Pool Time Server)

If your system uses rc scripts, what is an easy way to start the NTP daemon?

rcntp

System time is measured in what unit of time since what day?

seconds, since Jan. 1, 1970

In the /etc/ntp.conf file, what is the syntax of a line which tells the NTP which servers you want to synchronize time with?

server time_server_IP_or_DNS_name e.g. *server pool.ntp.org*

If your system uses systemd, what command should be used to start ntpd

systemctl start ntp