A minimal systemd host synchronises its clock with systemd-timesyncd. Which statement about that service is accurate?
LPIC-1 Exam 102-500, objective 108. Essential system services hard
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The options
Not correct It is configured in /etc/ntp.conf, the same file ntpd uses.
Wrong. timesyncd reads /etc/systemd/timesyncd.conf (plus drop-ins under timesyncd.conf.d), where NTP= lists servers and FallbackNTP= lists the compiled-in fallbacks. ntp.conf belongs to ntpd and is not part of timesyncd's configuration.
Not correct It must be enabled with `chronyc set-ntp true`.
Wrong. chronyc controls chronyd, and set-ntp is not one of its subcommands. Synchronisation is toggled with `timedatectl set-ntp true`, which enables whichever supported NTP unit is installed.
Not correct It replaces the hardware clock, so hwclock no longer works on such systems.
Wrong. The RTC still exists and hwclock still reads and writes it. timesyncd simply keeps the system clock in step and lets systemd persist that time across reboots.
Correct It is an SNTP client only: it can set the local clock from an upstream server but cannot serve time to other hosts.
Correct. systemd-timesyncd is a lightweight client-side SNTP implementation. If the machine must answer time queries from other hosts you need a full server such as ntpd or chronyd.
Why
systemd-timesyncd deliberately implements only the client half of the protocol, which keeps it small enough to ship by default. `timedatectl status` reports both the timezone and whether NTP synchronisation is active, and `timedatectl set-ntp true|false` turns it on and off. Distributions that need a serving daemon or higher accuracy install chrony or ntpd instead, and those packages usually mask timesyncd so the two do not fight over the clock.
Where this comes from
- Cited
- LPI exam objective 108.1
- What it says
- Awareness of systemd-timesyncd as a client-side time synchronisation service.
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 108 and space the ones you get wrong.
More questions on this objective
- You corrected the running system's clock with `date -s`, but after the next power cycle the machine came back with the old wrong time. Which command copies the corrected system clock into the hardware (RTC) clock? machine-checked
- On a systemd-based distribution, which file determines the local time zone used by the C library when formatting times? machine-checked
- A host runs chrony as its NTP client. Which command shows the list of time sources chrony is currently talking to and how it rates each one? machine-checked
- In /etc/ntp.conf you find the line `server 0.pool.ntp.org iburst`. What does the `iburst` keyword do? machine-checked
- On a systemd host, type the single command that turns on automatic network time synchronisation (do not include a path). machine-checked
- You have just set the system clock correctly by hand and want the hardware clock to match, so the correction survives a reboot. Type the command, using its short option. machine-checked