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Okay, in this video I want
to show you what's going on

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with Cron. So to start with
sudo systemctl status on crond service.

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Sometimes it's crony, sometimes it's
cron, depending on your distribution.

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But here we can see
that cron is actually running.

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Now this cron service
has its main configuration file.

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If I use sudo cat on etc crontab
then we can see what it is like.

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Historically you would put everything in here. That's
not how we do it nowadays anymore. But I

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like it because it has an explanation of
the times. So it has five positions to indicate

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the minute, the hour, the day of the
month, the month and the day of the week.

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And based on that I
can create my own crontab.

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And in order to do so,
I'm going to use sudo crontab E

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for edit, U for lynda. I
want to create a crontab for user

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lynda where I'm going to
set star star star star star.

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Oh my goodness. Really? Yeah, I want to do it
every minute because I want to show you that it works.

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And I am
going to use logger.

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Greetings
from Linda.

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Now what did we just do? Well, I
just created a new cront app for user

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Lynda, E started the editor and U is
doing it for a specific user. That's what

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I like about crontab. You can easily create
tasks that will be executed by specific users.

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Now normally it will do so on top of the minute. That's why I've
done every minute. In real life you don't want to do it every minute.

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But now I want to make
sure that we can see a result.

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So are we already on the
top of the minute? Well, seven

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more seconds of waiting and
then we should see the result.

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So I'm going to
use sudo journal ctl.

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Now, what is journal CTL showing? Well, journal CTL
should show on top of the minute and oh

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boy, a lot of things have happened on top
of the minute. But that includes greetings from Linda.

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Journalctl is the easiest way to
get more information out of the

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systemd journal. That's a topic we'll
talk about later by the way.

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So this is one thing that
you can do with cron. Now, depending

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on your distribution, you might have
Kron automatically pickup configuration files if that

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is the case. Well, you are
going to find out by using lsetccronestar.

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And what you would be looking for is
if you have anything, any directories and any files

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in there here on Centos we don't. But
let's check out how it works on Ubuntu.

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So here I'm on Ubuntu
and I'm using LS on Etc.

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Cron and there you can see that there's
a couple of subdirectories. So there is the

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Etc Cron D which has cron jobs that
will be picked up by the cron daemon.

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There is Etc. Cron daily,
weekly, monthly, which is cron jobs

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that will be executed at
a daily, weekly and monthly basis.

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Like mandb
for instance.

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So this Ubuntu system is running mandb
every day now everything in the cron

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daily, weekly or monthly directories is a
shell script that will be picked up

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automatically and stuff in etc. Cron
D should have regular cron syntax.

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So when I would
check etc. Cron D

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systat we can see
what it is doing.

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I like this command because it
has a little bit more complex syntax.

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What do you think of this for
5,55,10 that means starting at minute 5

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until minute 55 of every hour of
every day of the month, in every

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month and every day of the
week it will run this command.

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We also see a second
one, 5923 which means every day

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at hour 23, minute 59
it will run this other command.

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That is what these cron files may
look like now. You should know that

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cron is from the past and distributions
are moving on to systemd timers nowadays.