August 2021
Intermediate to advanced
542 pages
11h 16m
English
Content preview from Linux Cookbook, 2nd Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 17. Keeping Time with ntpd, chrony, and timesyncd
Keeping accurate time on your computer, and on all hosts on your network, is easy and automatic with NTP, the Network Time Protocol. NTP is implemented on Linux with ntpd, the NTP daemon, chrony, the modern replacement for ntpd, and systemd’s timesyncd. That is right, friends, there are three (at least), count them, three ways to automatically manage time on your Linux computer.
ntpd and chrony can also function as LAN time servers, while timesyncd is a simpler lightweight client with no server functions. ntpd and chrony are full NTP implementations, while timesyncd uses SNTP, the Simple Network Time Protocol.
Most Linux distributions provide a default configuration that points to time servers that they maintain. These servers have names like 2.fedora.pool.ntp.org and 0.ubuntu.pool.ntp.org. You don’t have to do anything, except be sure to not disable this during installation. In this chapter you will learn how to check your current settings, how to change them, and how to set up a LAN time server.
There is a worldwide network of time servers that are free for everyone to use, and they are organized into strata, starting at stratum 0. Stratum 0 is the source for all timekeeping, a network of atomic clocks, radio receivers tuned to atomic clocks, and GPS receivers using signals broadcast by GPS satellites.
Next in line is stratum 1, where the primary time servers reside. The primary time servers in stratum 1 are directly ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.