[Deep Dive]

[Setting up a Server - Introduction to Package Managers]

[with Jim Hoskins]

Whenever we can, we are preferred to use a package manager

to install our software.

Besides making installs easy, it has many other benefits

like managing dependencies, handling updates, and uninstalling.

The package manager for Ubuntu Linux is called APT.

Ubuntu is actually a member of a family of Linux distributions

that are based on Debian Linux.

Linux comes in many different flavors and while they share the same core,

the tools and configurations and options

vary from distribution to distribution.

There are many different package managers for Linux,

and they vary from distro to distro.

APT is what is used for Debian-based Linuxes

and its related distros.

Some others are Pacman, RPM, and YUM

on the various other distros.

Mac OS X even has its own package manager called Homebrew

that you can install and use.

Let's learn the basics of using APT on our Ubuntu Linux console.

So we saw how to install a program from source.

We don't usually need to do that.

Instead we can use our package manager.

We used it briefly to install our initial build tools.

Now let's take a look at our tool in a little more depth.

APT or the advanced packaging tool is the package manager

we use on Ubuntu Linux, as well as some other distributions

of Linux based on Debian.

One of the first things that you should do is to run sudo apt-get update.

This command will update our local databases

of the available packages.

You'll want to run this every once in awhile.

This will make sure that our database has the complete list

of packages up to date including the most up-to-date versions.

If you attempt to install something

and you have not run update in awhile, you may find that packages

are unavailable because our local database is out of sync

with what's really available.

So it's a good idea to run sudo apt-get update every once in awhile.

Now you may have to type in your password

depending on how recently you've used the sudo command.

If it looks like this, everything should be up to date.

I'm going to go ahead and clear our screen.

So let's say I wanted to install the program Git.

Git is a version control system that is very popular

for managing the source code of our applications.

There should be a Git command on our system.

If we try to type it, we'll see a message come back

from our operating system saying,

"The program Git is currently not installed."

It's actually telling us how we can install Git using the APT system.

Sometimes when you try to run a command

that you don't have installed, it'll simply say it's not found.

But Ubuntu is a very friendly operating system,

and it recognizes that Git is a thing;

however, it's just not a thing it has installed,

so it gives us this nice little tip.

So if we wanted to find out how to install Git,

we could just listen to this prompt and type sudo apt-get install get.

But I want to show you how you can search for things

using the APT system.

We can use a program called APT-Cache.

And one of the commands that APT-Cache allows us to use is search.

And this allows us to search for packages based on a pattern.

So let's say we wanted to find the packages

that have the word Git in them.

Now there's quite a few of them, and if we want to scroll through

we can see what they all are with a brief description.

Now I'm pretty sure that the package that we're looking for is called Git.

But sometimes there's a specific package name

that may not be obvious to you,

so using a search like this can be useful.

Now once we've looked through the list of programs we want to install

and found what we're looking for, the apt-get install is what we'll use.

Let me clear our screen and we can run sudo apt-get install get.

Now it's given us a little bit of information

about what it's about to install.

One of the really nice features of a package manager

is that it understands the dependencies that programs have.

For instance, when we install Git, there are other tools

that it depends on in order to run.

Those tools we can see here are also the extra packages

that are also going to be installed.

It even gives us some suggestive packages

that will compliment the install that we're running nicely.

So it's saying we're about to install 3 new packages,

and it doesn't need to update or remove anything else.

It even gives us a little bit of information

about how much disk space is going to be used.

We have a confirmation here.

We can type in y to continue or n to cancel.

It looks good to me, so I'll hit y, and it's going to go ahead

and download it, install it, install all the documentation that we need,

and then we'll be done.

So if I type in clear, I can type in which git.

We can see that Git is now installed.

I can run Git, and it's giving me the help command,

and everything looks good.

Let's go ahead and clear the screen.

Now we've installed our software, but every once in awhile

we may want to make sure that we're keeping our software

up to date.

For instance, a new version of Git or any of the other tools

we have installed on our system may come out.

So it's good to periodically upgrade our packages.

In order to do this, we can run sudo apt-get upgrade.

This is a good program to run.

Not only to make sure we have all the latest features

of all of our packages, but there may be security updates

that are going to make our computer safer to use.

And we want to make sure we have all of the latest security patches.

This will allow us to do it.

So we're using the same apt-get command,

but now we're doing upgrade instead of install.

Now by fault it's going to upgrade the packages that it knows about.

You'll usually want to run the upgrade command

after you've done an update.

If we haven't updated our system,

it won't be aware of any new packages,

so run sudo apt-get update then sudo apt-get upgrade.

So again it's giving us a confirmation, and it's telling us

about all the things that is about to upgrade.

Some of the things it will not upgrade,

and some of the things it will.

And we can see there are quite a few packages

that are about to be upgraded.

There's 118 packages we're about to upgrade, and it didn't

require us installing any new ones or updating anything else.

It's telling us it's going to download about 70 megabytes,

but it's only going to increase our disk space by 610 kilobytes.

Again this all looks good to me, and so we can just go ahead

and hit y and run it.

Now since there are quite a few upgrades that are going to happen,

this command may take a little while to run.

But after we do, all of our packages will be up to date and ready to go.

And now our sudo apt-get upgrade has run,

and our packages are up to date.

Finally, a common thing you might want to do is uninstall the program.

To uninstall, we'll type sudo apt-get remove

and the name of the package.

Let's uninstall Git since that's what we most recently installed.

Now it's only going to remove the package that we named.

Remember those 2 packages that it installed because we installed Git?

Those 2 are not going to be uninstalled by just typing 'remove'.

In fact, it tells us this.

It says, "The following packages were automatically installed

but are no longer required once we remove Git."

Later we can run sudo apt-get autoremove to remove

any dependencies that were installed

by consequence of installing it on a package that is no longer needed.

It keeps track of this for us and knows that installed things like

git-man and liberror-perl because we installed another program.

Once we uninstall the program that required them,

it's able to automatically clean itself up

using the app-get autoremove command.

For us we really don't need to worry about it.

If we want to save on space, we can use the autoremove to do that.

But for now let's just worry about removing the Git package,

and not worry about it's dependency.

Again it confirms with us, and through it we'll just hit y and enter,

and it's going to remove the Git command from our system.

So if we type git, there is no such file or directory.

You'll notice that it has now changed to a different error message

than we used to have.

Before, it told us that we could install it with the apt-get install command;

however, now we get these normal cannot find usr/bin/git.

It's been removed.

If we ever want to have Git installed again,

we can simply do sudo apt-get install git, and it'll all work.

Now the packages can be used to install all sorts of things

from utilities like Git all the way up to things like servers like Apache,

databases like MySQL or even SQLite,

which we previously installed from source.

I recommend any time you need to install something,

checking to make sure it's available in your package manager.

It's much easier to install as well as manage.

And when you need to, it's also easier to uninstall

than if you had installed from source.