Managing Services in Linux

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From the course by Google

System Administration and IT Infrastructure Services

2837 ratings

Google

System Administration and IT Infrastructure Services

2837 ratings

Course 4 of 5 in the Specialization Google IT Support Professional Certificate

This course will transition you from working on a single computer to an entire fleet. Systems administration is the field of IT that’s responsible for maintaining reliable computers systems in a multi-user environment. In this course, you’ll learn about the infrastructure services that keep all organizations, big and small, up and running. We’ll deep dive on cloud so that you’ll understand everything from typical cloud infrastructure setups to how to manage cloud resources. You'll also learn how to manage and configure servers and how to use industry tools to manage computers, user information, and user productivity. Finally, you’ll learn how to recover your organization’s IT infrastructure in the event of a disaster. By the end of this course you’ll be able to: ● utilize best practices for choosing hardware, vendors, and services for your organization. ● understand how the most common infrastructure services that keep an organization running work, and how to manage infrastructure servers. ● understand how to make the most of the cloud for your organization. ● manage an organization’s computers and users using the directory services, Active Directory, and OpenLDAP. ● choose and manage the tools that your organization will use. ● backup your organization’s data and know how to recover your IT infrastructure in the case of a disaster. ● utilize systems administration knowledge to plan and improve processes for IT environments.

From the lesson

Network and Infrastructure Services

In the second week of this course, we'll learn about network and infrastructure services. We will cover what IT infrastructure services are and what their role is in system administration. We'll also learn about server operating systems, virtualization, network services, DNS for web services, and how to troubleshoot network services. By the end of this module, you will know the most common IT infrastructure services you'll encounter when handling system administration tasks.

What do Services Look Like in Action2:08

Managing Services in Linux4:59

Managing Services in Windows3:40

Configuring Services in Linux4:55

Configuring Services in Windows4:51

Meet the Instructors

Google

As a system administrator,

you will need to know how to look at the status of a running service and how to stop,

start and restart running services.

The exact way to do this would depend on the operating system you're using,

but the concepts are the same.

Let's look at a very simple service;

Network Time Protocol, NTP.

We've caught out before that NTP allows machines to synchronize their clocks.

Ubuntu installations include a daemon that runs on

the machine and is in charge of synchronizing the clock using NTP.

We can check that there's an NTP daemon running on

this machine using the service command, Service NTP Status.

We can see that there is an NTP service and the system tells us it's running.

This service is keeping our clock on time without us even realizing it.

If at any point it detects that the clock has drifted,

it adjusts the time in a very small increment.

It will add or remove 0.5 milliseconds per second until it reaches the desired time.

It uses very small increments so that

other services which depend on the clock to perform their tasks,

won't be affected by a sudden adjustment of the time.

Under normal operating conditions,

a computer clock will only see very small drifts from the standard time.

So, these very small adjustments make sense.

If the daemon detects the time has changed more than 128 milliseconds,

it assumes that something else is going on and will not interfere.

Let's test this by manually modifying the date of the system to a date in the past.

So, I'm going to go ahead and type in sudo,

date and give it a specified date,

2017-01-01 00:00:00 and that specified date,

hit Enter and then type in date.

We've set the date to January first,

2017 at 12 AM.

If we check the date after a few seconds,

it will still be set to January first,

2017 a few seconds past midnight. It does not get adjusted.

The NTP daemon sought to change but since it's more than 128 millisecond threshold,

its not adjusting the clock.

So, how do we make it catch up to the present.

There's an option in the NTP daemon that allows

it to drastically adjust the clock when it's starting.

This is because the daemon is expected to start very

early in the process when the machine is booting up.

So, there shouldn't be any time dependent services running at that point.

If we manually restart the service now,

we'll see that the date and time get adjusted.

So, let's type in sudo, service, ntp stop.

Typing date, sudo service ntp

start and then typing date, then Enter.

We use the stop action to stop the service and the start action to start it back up.

Immediately after starting the service,

we can see that the date and time are set back to the present.

We use the sudo command to stop and start the service because any user can check

the status of the service but only an administrator can cause it to stop and start.

An alternative that's available in most services is the restart action,

which does a stop followed by a start.

Let's see how that one looks.

First, let's set that date back to January first,

2017 at 12 AM and then we'll restart the NTP service.

So, I'm typing in sudo,

date, specify the time.

So, 2017-01-01 00:00:00, hit Enter.

Then hit date, then hit

sudo service ntp restart,

then hit date.

Now you've seen how to check the status start,

stop and restart service in Linux.

NTP is a very simple service,

but you can also use the same commands to manage much more complex services.

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