ntp server configuration (LAB 11.3)

Hello,
There are some things I don't understand concerning ntp, if someone could clarify I would be very grateful.
First, since the same file /etc/ntp.conf is used for client AND server configuration, how does the daemon know if it's a server or a client ? Or it is always both server and client at the same time (since I guess it has to get the correct time from somewhere unless it's stratum 1) ?
In Lab 11.3 solution it's suggested to add following lines to /etc/ntp.conf:
server 0.pool.ntp.org server 1.pool.ntp.org server 2.pool.ntp.org server 3.pool.ntp.org
On my system (ubuntu server 20.04) that doesn't do anything (visible at least). I had to change server for pool as in pool 0.pool.ntp.org
for the solution to work.
In the course (LFS 211) it says:
It may be desirable to declare the local machine as a time source:
server 127.127.1.0
fudge 127.127.1.0 stratum 10
So, I guess the server is used to start a local ntp server ?
Bottom line question, what's the difference between server and pool keywords ?
Second thing a bit confusing for me is the syntax for allowing client connections:
# Default policy prevents queries restrict default nopeer nomodify notrap noquery # Allow queries from a particular subnet restrict 123.123.x.0 mask 255.255.255.0 nopeer nomodify notrap # Allow queries from a particular host restrict 131.243.1.42 nopeer nomodify notrap noquery # Unrestrict localhost restrict 127.0.0.1
First it says default policy prevents queries and I see a logical restrict ... no something something but then
to unrestrict localhost we add restrict 127.0.0.1 and to allow queries for a particular host we add noquery... ?
Is it just me or this is a bit counter intuitive ? What's the logic behind this ?
Thanks in advance for your time !
P.S.
In the course LFS211 > Advanced Networking > NTP Applications
I think the expand title /etc/ntp.confntp should be /etc/ntp.conf (?) and also the NTP link once we expand the tab is broken
Comments
-
You have some good questions, @k0dard. I don't have any "ntp" packages installed anywhere to dig into, but I do have a recommendation.
The most-recent way to use NTP is via
timedatectl
command.Also, systemd-timesyncd.service and /etc/systemd/timesyncd.conf come into play for finding out which NTP server may have been assigned, and for assigning an NTP server respectively.
On Ubuntu 20.04,
timedatectl timesync-status
will show which NTP server is in use, but without any command args passed to it, it will simply state the date, time, TZ, if sync'd, if NTP active, and Real Time Clock info.Seems the NTP packages are a bit deprecated.
0 -
The NTP packages are no longer available on RHEL/CentOS 8. timedatectl and chrony are installed by default.
0 -
Thanks for your answers.
I know about timedatectl, the question was on doing the course lab and also understanding ntp.conf.
Even if it is deprecated as you suggest, aren't there still servers out there that use it ?
0 -
it is not just deprecated in RHEL 8/ CentOS 8, it is gone. I'm not an expert but i'm sure any distro is still ntp servers. For example on RHEL8, in
/etc/chrony.conf
at the top thee are the lines:# Use public servers from the pool.ntp.org project. # Please consider joining the pool (http://www.pool.ntp.org/join.html). pool 2.rhel.pool.ntp.org iburst
I don't personally know chrony, but you obviously can put the servers you want there.
0
Categories
- 8.9K All Categories
- 13 LFX Mentorship
- 66 LFX Mentorship: Linux Kernel
- 363 Linux Foundation Boot Camps
- 230 Cloud Engineer Boot Camp
- 70 Advanced Cloud Engineer Boot Camp
- 25 DevOps Engineer Boot Camp
- 5 Cloud Native Developer Boot Camp
- 845 Training Courses
- 15 LFC110 Class Forum
- 16 LFD102 Class Forum
- 102 LFD103 Class Forum
- 3 LFD121 Class Forum
- 55 LFD201 Class Forum
- 1 LFD213 Class Forum - Discontinued
- 128 LFD232 Class Forum
- 19 LFD254 Class Forum
- 431 LFD259 Class Forum
- 85 LFD272 Class Forum
- 1 LFD272-JP クラス フォーラム
- 16 LFS200 Class Forum
- 692 LFS201 Class Forum
- LFS201-JP クラス フォーラム
- 271 LFS211 Class Forum
- 50 LFS216 Class Forum
- 26 LFS241 Class Forum
- 27 LFS242 Class Forum
- 19 LFS243 Class Forum
- 6 LFS244 Class Forum
- 9 LFS250 Class Forum
- LFS250-JP クラス フォーラム
- 107 LFS253 Class Forum
- 789 LFS258 Class Forum
- 7 LFS258-JP クラス フォーラム
- 51 LFS260 Class Forum
- 78 LFS261 Class Forum
- 13 LFS262 Class Forum
- 76 LFS263 Class Forum
- 14 LFS264 Class Forum
- 10 LFS266 Class Forum
- 8 LFS267 Class Forum
- 9 LFS268 Class Forum
- 6 LFS269 Class Forum
- 180 LFS272 Class Forum
- 1 LFS272-JP クラス フォーラム
- 187 LFW211 Class Forum
- 103 LFW212 Class Forum
- 878 Hardware
- 207 Drivers
- 74 I/O Devices
- 43 Monitors
- 115 Multimedia
- 204 Networking
- 98 Printers & Scanners
- 82 Storage
- 723 Linux Distributions
- 81 Debian
- 64 Fedora
- 12 Linux Mint
- 13 Mageia
- 22 openSUSE
- 126 Red Hat Enterprise
- 33 Slackware
- 13 SUSE Enterprise
- 347 Ubuntu
- 447 Linux System Administration
- 33 Cloud Computing
- 64 Command Line/Scripting
- Github systems admin projects
- 89 Linux Security
- 73 Network Management
- 105 System Management
- 45 Web Management
- 50 Mobile Computing
- 18 Android
- 19 Development
- 1.2K New to Linux
- 1.1K Getting Started with Linux
- 499 Off Topic
- 119 Introductions
- 193 Small Talk
- 19 Study Material
- 747 Programming and Development
- 240 Kernel Development
- 473 Software Development
- 902 Software
- 247 Applications
- 178 Command Line
- 2 Compiling/Installing
- 72 Games
- 314 Installation
- 20 All In Program
- 20 All In Forum
Upcoming Training
-
August 20, 2018
Kubernetes Administration (LFS458)
-
August 20, 2018
Linux System Administration (LFS301)
-
August 27, 2018
Open Source Virtualization (LFS462)
-
August 27, 2018
Linux Kernel Debugging and Security (LFD440)