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- Okay, so now we're gonna
take a look at Terraform itself

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as a tool, now that we have it installed.

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So Terraform, as I mentioned before,

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is a command line interface tool, or CLI.

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And it has a number of sub-commands.

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You can see we've got 10
or 15 sub-commands here.

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Only three that you
use on a regular basis.

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And those are, in order, init, okay?

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So the description here is

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initialize a Terraform working directory.

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That's not terribly helpful.

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What init does is it
downloads Terraform providers

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or makes sure that they
already exist, okay?

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And we're gonna get much deeper

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into what providers are later on

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but I can tell you right now

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that those are the interface
to individual cloud services.

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For example, there's an AWS provider,

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there's a Google provider,

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there are providers for things

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that may not seem like cloud at all,

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like there's a GitHub provider.

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There's a G-Suite provider.

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So the providers are very, very important.

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So init does two things.

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It downloads or ensures that

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the providers referenced
in the config are available

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and then it also ensures

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that any modules referenced are available.

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And we're gonna get into
what modules are here

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in a few lessons.

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You don't have to worry
about that right now.

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But those are basically pieces
of code that either you wrote

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or that it downloads from the internet.

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So init must be run on
any Terraform directory

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before you can proceed to
the next step, which is plan.

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Okay?

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So what plan does,

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if you'll remember a few slides ago,

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we showed the config and
the state being compared.

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That's what plan does.

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Plan prepares the configuration

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so what you're telling Terraform

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that you want the state of the world to be

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with what Terraform thinks
the state of the world is.

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And then the output from
that step is a detailed plan

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of exactly everything that
Terraform is going to change

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in order to get there.

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So that plan will display in the console

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all the changes that it's going to make.

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And if you tell it to, it
will also create a plan file.

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And the plan file is used for
the next step, which is apply.

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Okay?

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Apply simply tells Terraform
to make the state of the world,

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reflect the configuration
that you've given it.

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And you can either give it a plan file

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or it will run the plan step for you

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and then you'll have to confirm
that you want to run it.

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It's always best practice to
run plan with an output file.

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And we'll be using these steps

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throughout the entirety of this training.

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So in addition to those,

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Terraform has lots of other commands.

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We've got about 12 other commands here.

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Destroy is also one that you
may use on a regular basis.

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So what destroy does is tells Terraform

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to take that state file,

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so all the resources that
Terraform has created,

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and destroy them.

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So this is common in
development environments,

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but you have to be careful
with it, obviously,

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because it can also destroy
your production database.

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Fmt, or format, you can
see the description,

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rewrite config files to canonical format.

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So what that does, and
this is somewhat common

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in tools that are written in go,

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is that rather than allowing
everybody to have an opinion

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about what the formatting
of the files should be,

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Terraform just goes ahead and tells you.

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So you can run this format command

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against your Terraform config files.

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And it will do things like
convert tabs to spaces

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and align the indentations
and things like that.

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So things that aren't necessarily
syntactically incorrect

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it will change for you.

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So it's a good practice
to run the format command

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before you do something like

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check your code in to get up for example.

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Okay get is rarely used.

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This simply downloads and installs modules

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for the configuration.

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That's something that's
normally handled by init.

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Graph, we'll talk about graph later,

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but it will display the
dependency tree of the resources.

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And when we talk about
the config language,

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we're gonna talk about
dependencies quite a bit.

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Import is an important one.

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This one is used if you have resources

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that have been created
without using Terraform,

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so if you already have
a whole AWS environment

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and you would like to begin
managing that in Terraform,

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you'd use the import command.

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And we'll talk about how to do that later.

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Unfortunately, it's pretty tedious.

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There's not a good way from
within Terraform itself

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to sort of import in an
entire infrastructure.

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So it's sort of one piece at a time.

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Outputs, we'll talk about outputs later,

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but this will simply display on the screen

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any outputs that are defined

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in your Terraform configuration.

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Providers, we talked about
Providers a little bit,

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but this command also rarely used,

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but it will tell you sort
of the dependency tree

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of the providers.

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Refresh will update the local state file

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against real resources.

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So if you have some drift in there,

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you may be able to detect
that with the refresh command.

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The show command will simply
display some information

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about your state or your plan file.

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Taint is an interesting one.

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So taint will mark a resource
as needing to be refreshed

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within the configuration.

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This one needs to be used occasionally.

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It's somewhat rare.

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I would say that it's sort
of an advanced use case.

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I do use it regularly,
but it's usually a sign

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that there's something wrong
with your configuration

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that needs to be addressed otherwise.

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Untaint, I've never used untaint.

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I guess if you've inadvertently
tainted something,

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you can untaint it.

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Validate is similar to a
lint or just a syntax check.

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So validate will run
against your config file

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and just simply tell you whether
the syntax itself is valid.

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So it's a good idea to run this

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as part of your something
like a get pre-commit hook,

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for example, so you
don't check typos in it.

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We'll talk about this a little bit

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when we get into the
continuous deployment section.

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Version you already saw.

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This simply tells you

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what version of Terraform you're using.

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And then workspace we'll get into

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during the collaboration section.

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But a workspace in
Terraform is essentially

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an alternative version of the state.

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So you can do things like run

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different stages of development
using the same config files.

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So you can have a dev staging
and production workspace,

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for example, is a pretty
common use for that.

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And then there are some
other commands here

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that are less commonly used.

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The 0.12upgrade command,

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in between Terraform 0.11 and 0.12,

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the configuration language was
changed very significantly.

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So the 0.12 upgrade commands
will attempt to take

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a earlier version of your config

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and convert it to something
that's compatible with 0.12.

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This debug command will basically turn on

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verbose output of your commands.

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There's other ways of doing that

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using log settings and so forth.

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Force unlock is used when the
state file becomes locked.

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When you're doing plan or apply

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or some of these other commands.

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They will enforce a lock on the state file

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so that somebody else doesn't
work on it at the same time.

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And sometimes if Terraform crashes,

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or if you cancel it in certain ways,

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that state can be locked infinitely.

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So sometimes you need to
go in and force unlock it

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if something has crashed or
something has gone wrong.

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Sometimes that locked file
will become permanently locked.

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And then the state command,

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well there's a push command

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and you can see that
they've called it obsolete.

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So that's one unused.

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But the state command is used for

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interacting with the state file.

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Occasionally, especially
during development,

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you may need to manually delete

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something from the state file.

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Or if somebody has gone
into another management tool

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and deleted a resource, for example,

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like they've gone into the AWS console

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and they've deleted something

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and didn't realize that it
was managed by Terraform,

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you may need to go into the state file

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using this state command
and remove that resource.

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We'll talk about that

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in the debugging and
troubleshooting section.