A workstation dual-boots with an operating system that keeps the real-time clock in local time, so Linux must not assume the RTC holds UTC. Which file records whether the hardware clock is interpreted as UTC or as local time when hwclock is invoked without --utc or --localtime?
LPIC-1 Exam 102-500, objective 108. Essential system services hard
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How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Correct /etc/adjtime
Correct. Its third line is the literal word UTC or LOCAL. The same three-line file also carries the drift factor in seconds per day and the epoch of the last adjustment.
Not correct /etc/localtime
Wrong. That is the binary tz-database file (usually a symlink into /usr/share/zoneinfo) describing the local zone's offsets and DST rules. It says nothing about how the RTC is stored.
Not correct /etc/timezone
Wrong. On Debian-derived systems this holds the zone name as one line of plain text, for example Europe/Lisbon. It mirrors /etc/localtime and is not consulted for the RTC's mode.
Not correct /etc/sysconfig/clock
Wrong on current systems. It was the Red Hat file that carried a UTC=true setting for the init scripts; current util-linux hwclock does not read it.
Why
hwclock has no way to tell from the RTC itself whether the value it holds is UTC or wall-clock time, so the answer must be stored, and /etc/adjtime is where it lives. `timedatectl set-local-rtc 1` is the systemd front end that rewrites that line for you. Keeping the RTC in local time is discouraged because there is no clean way to handle the ambiguous hour at a DST change.
Where this comes from
- Cited
- manual page adjtime(5)
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
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