Hands-on Lab·LPIC-1
Time synchronisation and the system clock
Objective 108.1 is time, and it is worth more attention than it usually gets: a clock that is wrong breaks TLS, Kerberos, cron and every log correlation you will ever attempt. This guide separates the three clocks a Linux machine has, shows how far off this one is and which server it is following, and is precise about the difference between a time zone and the time.
102: Essential System Services Guide 18 of 33 Beginner
- PlatformsUbuntu 26.04 LTS + AlmaLinux 10.2
- TimeAbout 18 min
- RPM packagingrpm 4.19.1.1, dnf 4.20.0
| Server Name | IP Address | OS | Roles | CPU | RAM | HDD |
|---|---|---|---|---|---|---|
| LPIC1-A01 | 192.168.0.76 | Ubuntu 26.04 LTS | Debian-family host - dpkg and apt, which objective 102.4 names | 2 Core | 4 GB | 50 GB |
| LPIC1-B01 | 192.168.0.77 | AlmaLinux 10.2 | RPM-family host - rpm and dnf, which objective 102.5 names | 2 Core | 4 GB | 50 GB |
This guide includes
Use this for an objective that gets less attention than it earns. This matters because there are three clocks and only one is authoritative - and changing the time zone does not change the instant.
- reading all three clocks at once, and finding which one is authoritative
- asking how far off the clock is, and whom it is following
- changing the time zone, and proving the instant did not move
Before you start
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Three clocks, and which one is authoritative
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How far off, and following whom
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A time zone is not the time