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- In this video, I want
to explain time in Linux.

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It all starts with hardware time.

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Hardware time is a time that's kept

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in the hardware clock,

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that's on the motherboard
of your computer.

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When your computer is booting,

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the only thing that it
has is hardware time.

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So then you boot your operating system

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and your operating
system needs system time

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and the system time is obtained
from the hardware time.

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So that means that the
hardware time is leading

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and it's important that your
hardware time is set all right.

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Now, how can we manipulate that?

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Well, in Linux, we have utilities,

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we have hwclock,

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hwclock is the utility

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that you can use to
manipulate the hardware time

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and we have utilities like timedatectl,

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which is a preferred
utility for managing time

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in the operating system right now.

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if we have timedatectl,

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why would you want to manage
the hardware time as well?

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Well, that is because the
timedatectl utility writes here

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and if you have a problem
or a serious difference

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between hardware time and
operating system time,

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the next time you reboot,

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your operating system will
have the wrong time available

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and that is why hwclock is
a very relevant utility.

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You can even use hwclock
to synchronize the time

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between the hardware
time and the system time

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and that is pretty important

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that you are doing that all right

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because next, your operating system time

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often is synchronizing using
NTP, the Network Time Protocol

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but NTP is synchronizing
with external service

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to make sure that you get
the time from the internet

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and that's only going
to work out all right

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if the differences falls within
a tolerance of 1000 seconds.

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So that means that if your
operating system clock is off

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by more than 1000 seconds,

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because a problem in your hardware time,

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you won't get any time synchronization

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and time is very important
for services on Linux

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and that is why you better make sure

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that it works right before
you do anything else.