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I've set up a fresh Ubuntu
server with RBM, PostgreSQL and

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NGINX at a hosting company.

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If you need help setting these
packages up see the teacher's notes.

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If you'd like to follow along using
a virtual machine instead of an actual

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server you'll find info in
the teacher's notes for that too.

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I have not installed Rails or Unicorn, nor

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have I manually deployed my
Rails app to this server before.

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This is to ensure we have a clean
environment with no hard to troubleshoot

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conflicts.

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We're going to let Capistrano
handle all of those details for us.

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So let's exit back to our host machine.

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And first we're going to create
a simple Rails app that we can

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test Capistrano out with.

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So I'm gonna create a new Rails app.

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I'll say rails new, and we'll call
it captest, as in Capistrano test.

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Okay, then I'm gonna change
into that directory.

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Change directory captest.

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And let's bring this up in our editor.

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Okay, so first we need to
install the Capistrano Gem.

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We do that by editing our Gemfile.

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And there's already
an existing entry in there for

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the Capistrano-Rails Gem, so
I'm just going to uncomment that.

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I'll save that and go back to
the terminal and run bundle install.

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That will install the Capistrano Rails Gem
which has Capistrano itself as

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a dependency.

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Now, we need to set this new Rails
projects up to use Capistrano.

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We do that by running bundle exec cap

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install, that'll run the cap executable
which is included in the Capistrano Gem.

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The install sub command that we're running
here is going to create a several files

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that Capistrano needs to
work with our Rails project.

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Let's take a look at some of
the configuration files that Capistrano

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created for us.

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The first is named
Capfile with a capital C.

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It'll be in the rule of our project.

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It's mostly used for including y
variance that Capistrano requires.

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We're just going to use the default
set of libraries for now.

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So we'll leave this file alone.

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Next up is a file within the config
subdirectory named deploy.rb.

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It's used to set configuration variables
that'll be used to deploy your app.

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For this quick test, we're not going
to need these default variables, so

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let's get rid of them.

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And instead,

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let's create a new variable with a message
that we want to set up on our server.

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So we'll set message variable up,
by calling the set method.

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The first argument to set is a symbol
with the name of the variable

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you want to set up.

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And then we'll provide a string
with a value to set it to.

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Hello, Capistrano.

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Let's save that and we'll make use of this
variable later on when we set up the task.

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Next step,
Capistrano created a deployed directory

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which contains configuration files for
your various stages.

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Here we see two stages, the production
stage and the staging stage.

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The main thing you do in this file is
define servers for a stage that you'll

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need to deploy to, as well as any
variables that are specific to that stage.

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So here we're going to call
the server method to set up a server

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that we're going to deploy to.

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It's going to need an IP
address to deploy to or

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we could use a host name,
if we have one configured.

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So I'll paste that IP
address into a string.

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That's the first argument.

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Then the server method takes
a hash with various keys for

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various configuration items.

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The first key we're going to
wanna use is the user key which

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specifies a username that we're going
to log in and deploy the app as, so

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I'll use our deploy username for that.

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The next key we're going to want is
an array with a list of roles that this

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server plays within our app.

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The usual roles Capistrano uses are app,
db, and web.

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That's app as in the application server,
db as in the database server,

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and web as in the web server.

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A single server can fill
all three of those roles.

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For this quick demo though,
we're gonna create a new role, so

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I'll set up an array with
just a single item, and

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the role this server is going to
play is it's going to be a greeter.

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It'll store a simple greeting for us.

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That's all that we need to define for
our production server, so

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I'll just save this and
close out of that file.

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And we won't define anything regarding
a staging environment for right now.

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So we'll just leave that file alone.

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The last thing that Capistrano set up for
us is a lib, capistrano, tasks directory.

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Here we can create files that define tasks
that Capistrano needs to carry out when

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it's deploying an app.

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So let's create a new file
within this directory.

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And I'm going to name
it write_message.rake.

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It's important that the file extension
end in dot rake, instead of dot rb,

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so that Capistrano detects it.

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It uses .rake files because
Capistrano is based on another Ruby

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utility called Rake which stands for
Ruby Make.

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Rake is generally used to build
applications and Capistrano is just

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an extension of the rake syntax that
allows for the deployment of applications.

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So we've got our file created,
let's define a task now.

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First you're going to need to call the
desc method to define a description for

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your task.

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The description method takes a string
with the description to use cell.

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I'm going to say that this task
will write a message to a file.

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Then we actually define the task
by calling the task method.

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Task takes its symbols as its first
argument with the name of the task.

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We'll call it write_message.

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And then it takes block with
the actual task content.

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Normally task should only run on
servers that fulfill particular roles.

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We set up our production server
to fulfill the greater rule so

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we're going to specify that this task
should be run on greater servers now.

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We do that with the on method, then
we're going to call the roles method and

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pass it to return value to the on method.

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We need to pass the symbol
argument roles with

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the names of the roles
that it should work on.

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So we'll use a simple greeter and

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the return value of roles greeter
would then get pass to the on method.

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Now we need a block for the on method that
specifies what task we should carry out.

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Here we're going to use
a Capistrano method called execute,

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that specifies a command we should
execute on the remote server.

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Execute takes a string with
the command to send and

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it'll actually submit that
command to the server over SSH.

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So we're going to use the echo command
on the server, to take a string and

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append it to a file within our
home directory called message.txt.

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As for the content of that string
we're gonna write to the file,

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we'll get that from a capistrano variable.

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So I'm going to interpolate the result of
the ruby statement here into the string.

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And for that Ruby statement I'm going
to call the Capistrano fetch method

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which will fetch the value of a variable.

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We set the message variable up
in another configuration file.

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So I'm going to fetch that
message variable here.

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So the results of this statement is that
it will fetch the message variable and

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write it out to a file within
the home directory on the server.

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Let me save that, and
we'll go back to our terminal.

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We can get a list of all the tasks we
have defined by running the bundle

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exec cap command, and

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passing it a flag of -T,
to get a list of the tasks.

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There are quite a few tests that
have been predefined up here, but

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down here at the bottom,
we can see our tests defined.

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And as it suggests here,
we can invoke that with bundle exec

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cap write_message.

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Each task requires you to specify
a stage that you're going to run it on.

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And I neglected to do that so,

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I'm going to specify that this
should run on our production server.

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So I'll run the right message task.

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It alerts us to the command that
it's running on the remote server.

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And then it returns us to our shell,
indicating that the deployment is done.

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Let's go out to that server and
take a look at the results of our command.

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So I'm gonna copy the IP address here and
I'm gonna run ssh.

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I'm gonna login as the deployed
user at that IP address.

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And let's take a look at the contents
of our home directory here.

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We can see a new message.txt file.

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And if we take a look at its contents.

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There's the message that we specified
in our configuration files.

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Now of course,

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real deployment tasks that you set up
are going to be more complex than this.

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But this is a good demonstration
of how Capistrano works.

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In the next stage we're gonna
do something more useful, and

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use Capistrano to deploy Rails apps.