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Description

In this tutorial I'll go over how to setup a VPS instance (aka droplet) on DigitalOcean, transfer your code to it using git and FileZilla, and have the code run either all the time, and link to resources that explain how to run it periodically using cron. Links in the first section also have $10 signup bonus which you can use to get 2 months free VPS usage.

This tutorial is aimed at total beginners and will go over every step of the process with all the necessary code and screenshots being included and will not focus on the more advanced stuff. Because of the target audience I will not focus on some of the things that you should do when setting up a server such as using an ssh key, creating a new non-root user, fail2ban etc. but articles with more info will be linked at the bottom which you should read.

Every section will also have a short summary of the content - mostly so you can easily create notes or go over the steps again if necessary without reading the whole thing.

Overview

The tutorial consists of five sections:

  1. Creating a droplet (DigitalOcean calls their VPS instances "droplets").

  2. Accessing your droplet via SSH.

  3. Transferring files using FileZilla (SFTP), and getting code from remote sources.

  4. Using screen to create additional shell windows and running your code in a new screen session.

  5. Links for further reading

Requirements

DigitalOcean account and some funds on it, if you don't already have an account you can use this link to get $10 free signup bonus which is enough to run one instance for 2 months 24/7, DO also charges by the hour so you can destroy the droplet if you don't plan on using it a lot and you'll keep your money. Note: Adding a valid payment method to your account is required to activate the bonus - you will not be charged anything if you add your CC.

Basic familiarity with command line and python.

Software Used

I'll use Linux for screenshots, terminal for ssh access and running the commands, OS X should have ssh support in its terminal too. DigitalOcean also offers web version of terminal which should work on all platforms, you can access it by clicking on your droplet name on homepage and then clicking "Access" tab and choosing "Console Access". For windows there's also PuTTY that you can install and use.

For file transfers I'll use FileZilla, and I'll also show how to use git for pulling code from remote repository. For windows there's also WinSCP, but either will work.

1. Creating a droplet

Summary: Login to https://cloud.digitalocean.com, create a new droplet using Ubuntu 14.04 x64 image without using any SSH keys.


Once you've created your DigitalOcean account and have some funds in it (if you haven't check out the requirements section above) click on Create Droplet button and enter droplet name and change default size to $5/mo. or larger depending on your needs, I will go with the cheapest one.

Create Droplet Screen

Next there are region options, those don't really matter for now so just go with the default one. The default one being NYC3 in my case. Note that some of the additional available settings cost extra money, like enabling backups.

Create Droplet Region

Next on the page is the OS/Image options and SSH key options. For this tutorial I'll use Ubuntu 14.04 x64, the bit version doesn't matter and all of those distros probably come with all the necessary things already installed so you can pick whatever you want but if you're a beginner, and especially if you've never worked with Linux I'd recommend Ubuntu because it's the easiest one to find docs and support for from my experience.

SSH keys are a good idea, and will make changing the default password in the next step unnecessary, but for now I'll create a droplet without any extra SSH keys and will link to a tutorial how to add ones in the final section.

Create Droplet OS/SSH

Once you've got that click on "Create Droplet" button which should show this screen:

Creating Droplet Screen

After it's created check your email for droplet password, it should be emailed to you pretty much instantly.

DigitalOcean Email

Your new droplet will also show up on https://cloud.digitalocean.com/droplets homepage with the basic information like this:

Droplet homepage

2. Accessing your droplet via SSH

Summary: Use terminal and ssh@dropletIP or PuTTY on windows to establish a ssh connection to your newly created droplet.

Note: Replace 104.236.117.5 (or any other IP in this article) with your IP where you see IP address used in this article.

Linux/OS X

On linux you just open your terminal and enter ssh root@104.236.117.5 and enter the password given to you via email. You will also be forced to change the password after you've successfully logged in - you can use any password that you want. (Depending on the OS you will most likely not get any feedback while typing or copy/pasting your password, like * showing up instead of letters - but it is there)

Here's the screenshot of my terminal window after logging in and changing password

First login terminal

Windows

For windows using PuTTY you simply need to enter root@IP in the host name field, port as 22 (if not already set) and connection as ssh:

Putty Windows

After that you'll see the same window/console as you would on Linux - prompting you to enter password.

You can save your configuration, passwords etc. if you want inside PuTTY, but for now there is no need to do so.

3. Transferring your files to the server

Summary: Use FileZilla/WinSCP and SFTP to transfer files using GUI from your machine to your droplet. Use root as username, your droplet IP as host address and your new password you entered in previous step as password. For remote files you can use wget, git or some other VCS.


Since FileZilla is available both on Windows, Linux, and OS X I'm going to use that and SFTP to transfer the files. You can download FileZilla here or if you're on Linux you can install it from distro repos - on Ubuntu that would be apt-get install filezilla.

As far as connecting using FileZilla goes it's pretty simple:

In the main window toolbar there are fields to enter host, username, password, and port and a button to do a "Quickconnect". For host you simply enter the IP address of the droplet you created (visible when you login to your DO account and also given to you in email), username is root, password is the new password you entered in step 1 - not the one you got in your email, and port is 22. Once you've entered all that press "Quickconnect" button and you'll see some output below, it should look like this:

FileZilla quickconnect

If you get an error make sure all the necessary information is correct. Availability of this may (I am not sure) also vary with different distros.

If you get "Unknown host key" it is safe to click OK and continue with the connection and also you can add the host key to the cache to avoid prompts like this in the future.

Once the connection has been established in the panels below you can see your local files and folders on the left panels and the remote files and folders on the right.

FileZilla Folder View

Transferring files is as simple as dragging file from the left file panel to the right one. You can also create, remove and modify folders using FileZilla if necessary.

Remote sources

If you want to use someone else’s code, or your own, that's using git VCS - like something on GitHub fetching the code is simply a matter of running git clone <git url>. In case git isn't installed on your distro by default you can do so, on debian based OS, by executing apt-get install git.

If you want to get source from some other source doesn't use VCS you can use wget to download the file directly instead of downloading it on your machine and then transferring it using SFTP or something else.

This tutorial will not focus a lot on git, but you should definitely look into it and learn how to use it. I will link some resources in the final part.

4. Using 'screen'

Summary: Using screen -S name create a new windows session, Ctrl-a d to detach and screen -r name to re-attach it when needed. Run your code inside new window to prevent it from being shut down when you close the connection.


Note: All commands in this section are executed on your droplet, none of the commands are ran locally on your machine - so if you're not logged in to your droplet do so before continuing.

screen is a pretty powerful, open source, tool for multiplexing several virtual console windows. You can see complete docs for it here the only options I'll use in this tutorial are -S [name] for creating a new screen session named [name], -ls for listing active sessions, and -r [name] to attach to a running session named [name].

The reason for using screen and not just logging in and running python my_code.py is the fact that your process will stop being executed once you terminate connection to your droplet, which kind of defeats the purpose of having a remote droplet for running code 24/7 in the first place.

Other than screen there are also other tools that will do just fine for this purpose, however screen unlike those other tools is much more powerful IMO and generally good to know. There are also some other suggestions in this SO thread if you're interested.

If you want to run your script periodically then screen is probably the wrong tool for the job, so instead of keeping the code running for a whole week(for example) just to run once you should look into cron and how to schedule a cron job. Check out the next section with additional links and tutorials if that's the case.

The code I used in this example is:

#!/usr/bin/env python

import datetime
import time

def main():
    print "System time:" + datetime.datetime.now().strftime("%Y-%m-%d %H:%M")

if __name__ == '__main__':
    while True:
        main()
        time.sleep(5)

You can try running that without screen, then logging out, and then logging in to see what I'm talking about - the process will be stopped and there will be no traces of it once you log back in.

Creating a new screen session

First we need to create a new screen session, this is done by simpy running scren -S myScreen (myScreen being the name, you can use whatever you want) after that you don't get any special notification/message from screen but you should see a clear console with only root@YourDropletName:~#, this means you're in myScreen session.

You can now type python myCode.py and your code will execute just like you'd expect it. If you want to send it KeyboardInterrupt signal just press CTRL+C like you would on your own computer. Even if you closed your terminal now your code wouldn't quit.

Detaching and re-attaching session

To properly detach from the screen session hold CTRL then press a and then press d. All commands for screen are pre-faced with CTRL-a and then command letter.

To get a list of all active screen sessions type screen -ls which will show you a list of sessions like this

Screen sessions list

To access your screen session again, either after logging out and then back in or after detaching, type screen -r yourScreenName in my example it would be screen -r myScreen. Once you do that you should see all the output from your script that was printed while you were logged out, for the example code above it will look something like this:

Screen attached again

5. Further reading

Cron: If you want to schedule your script to run, for example, once per week, every 72 hours, once per month etc. then look into cron

http://www.unixgeeks.org/security/newbie/unix/cron-1.html

https://help.ubuntu.com/community/CronHowto

http://en.wikipedia.org/wiki/Cron

Securing your droplet

As mentioned in the first section the practices used in this tutorial work, but you should secure your production servers better if possible.

DigitalOcean has some pretty good tutorials on the subject:

https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-12-04

https://www.digitalocean.com/community/tutorials/how-to-setup-a-firewall-with-ufw-on-an-ubuntu-and-debian-cloud-server

https://www.digitalocean.com/community/tutorials/how-to-protect-ssh-with-fail2ban-on-ubuntu-12-04

https://www.digitalocean.com/community/tutorials/initial-server-setup-with-ubuntu-12-04

Using SSH keys with DigitalOcean

https://www.digitalocean.com/community/tutorials/how-to-use-ssh-keys-with-digitalocean-droplets

https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys--2

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Nikola Kovacevic

Software developer with six years of work experience, love python, django, c#. Working at an innovations center making clouds for dynamic hosting/IT infrastructure. Hobby guitar player.


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