Linux web services Part I

This is an introduction to a series of talks about setting up Linux servers. I’m going to make the assumptions that you already have some experience at the command line whether it is Mac or Windows so I will not be explaining basic commands in order to keep these talks with in a one-hour time frame. This talk will be done with the assumption you are using a Mac, but you can also follow along using cygwin on Windows.

Resources for this talk are available here https://github.com/icecreammatt/server-setup

Table of Contents

  • Public Private Key Creation
  • Instance Creation (DigitalOcean)
  • SSH Connection
  • Lockdown
  • Update & Upgrade
  • Software Installation
  • Configuration & Debugging
  • Shell Scripting
  • Git
  • Gotchas

Prerequisites

  • OSX Terminal or Cygwin
  • DigitalOcean hosting account or access to a fresh Ubuntu 14.04 install

Public Private Keys

To securely connect to a server we must not rely on passwords. So instead we use public/private key authentication. Using the same public keys that git uses for SSH we can also login to remote servers we configure to accept our key.

Key Generation

Before generating a key check to see if you don’t already have one.
If the output looks like below you can just use the existing public key to connect to the new server.

$ ls ~/.ssh
id_rsa      id_rsa.pub

Otherwise generate a new public private key pair.

$ ssh-keygen -t rsa -C "[email protected]"
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/matt/.ssh/id_rsa): id_rsa_example
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in id_rsa_example.
Your public key has been saved in id_rsa_example.pub.
The key fingerprint is:
e5:03:12:9c:40:7e:f3:f9:39:4c:1f:0b:07:04:7f:bd [email protected]
The key's randomart image is:
+--[ RSA 2048]----+
|   .oo.....      |
|   .  o. o   .   |
|    . + . + . .  |
|     . + = o   . |
|        S = o E  |
|         + * o   |
|          = o    |
|           .     |
|                 |
+-----------------+
$ ls
id_rsa_example     id_rsa_example.pub

The command below is specific to OSX and will not work in Cygwin
Copy the contents of the public key to the clipboard

IMPORTANT! Be sure to copy the file that ends in “.pub”

$ pbcopy < id_rsa_example.pub

If using cygwin navigate to C:\cygwin\home\username\.ssh\
Open id_rsa_example.pub in a text editor to copy the contents

$ cat id_rsa_example.pub
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDoROCEGpranbMr7Uj9Un3zPZAtYA4VgEqinTNSOnsJ5+oxpMrW0sV8/AUial3hxGVJK/UFsURmjGWg0liN9CGwNrnwGufDyG/SBpbRdFk8jwxLXQgiyTjbrNKlhhK0AWFTeajPsoXHE1jycEu4/G1oaewQ+se7055qsN3RIFLkpYj0VSsy/fjaZH5BPk+NtFQOc7yO7Nqs+x7nORsoLVyie2YhQSzzFBM23RMFmnf6qdrdARKwm98J8tpUqkILzCas9NG679fPxHMHGw/b2QPLr0I3LblE4c1IcIXIQPTniEm5lMjWkw7Ggf4AEg1PbWLcb5MvUwGuo8k6+ZsS1tYh [email protected]

Uploading Keys

  1. Login to DigitalOcean
  2. On the DigitalOcean dashboard select SSH Keys
  3. Add SSH Key
  4. Enter a name for it and paste the contents into the body.
  5. Create SSH Key

Instance Creation (Create Droplet)

DigitalOcean calls each server instance a “droplet”

xkcd.com/910

  1. Click Create Droplet
  2. Enter a hostname for your server
  3. Select a size (I recommend 512MB RAM for starting)
  4. Select Region
  5. Select Image Ubuntu 14.04 x64 (LTS)
  6. Add your key, which was uploaded earlier
  7. Create Droplet

SSH Connection

Once the loading bar has completed and we have an IP address we are ready to connect to the server.

We can connect to the server using the ssh command. Our public key has been automatically added to the server from the DigitalOcean control panel so our private key will work as the “password”.

$ ssh [email protected]
The authenticity of host '107.170.203.120 (107.170.203.120)' can't be established.
RSA key fingerprint is 5b:13:e0:0e:d9:44:5a:1a:49:b5:12:0e:3c:d4:0d:8d.
Are you sure you want to continue connecting (yes/no)?yes

After connecting you should see this.

Warning: Permanently added '107.170.203.120' (RSA) to the list of known hosts.
Welcome to Ubuntu 14.04 LTS (GNU/Linux 3.13.0-24-generic x86_64)

 * Documentation:  https://help.ubuntu.com/

  System information as of Fri Jul 11 01:06:53 EDT 2014

  System load:  0.0               Processes:           71
  Usage of /:   6.1% of 19.56GB   Users logged in:     0
  Memory usage: 9%                IP address for eth0: 107.170.203.120
  Swap usage:   0%

  Graph this data and manage this system at:
    https://landscape.canonical.com/

[email protected]:~#

Lockdown

We are now logged into the server, which right now is almost wide open to the Internet. It is time to lock it down with the following steps:

User account creation

Create a sudo user account

username=YOUR_NAME_HERE
addgroup admin
adduser $username
usermod -a -G admin $username

Full output

  [email protected]:~# username=matt
  [email protected]:~# addgroup admin
  Adding group `admin' (GID 1000) ...
  Done.
  [email protected]:~# adduser $username
  Adding user `matt' ...
  Adding new group `matt' (1001) ...
  Adding new user `matt' (1000) with group `matt' ...
  Creating home directory `/home/matt' ...
  Copying files from `/etc/skel' ...
  Enter new UNIX password:
  Retype new UNIX password:
  passwd: password updated successfully
  Changing the user information for matt
  Enter the new value, or press ENTER for the default
  	Full Name []: Matt Carrier
  	Room Number []:
  	Work Phone []:
  	Home Phone []:
  	Other []:
  Is the information correct? [Y/n]
  [email protected]:~# usermod -a -G admin $username

Copy over SSH public key to new account and set permissions to the owner

mkdir -p /home/$username/.ssh/
cp ~/.ssh/authorized_keys /home/$username/.ssh/authorized_keys
chmod -R 750 /home/$username
chown -R $username:$username /home/$username/

SSH Server lockdown

  1. Disable password authentication

    echo "PasswordAuthentication no" >> /etc/ssh/sshd_config

  2. Disable root login

sed -i 's/PermitRootLogin without-password/PermitRootLogin no/g' /etc/ssh/sshd_config
sed -i 's/PermitRootLogin yes/PermitRootLogin no/g' /etc/ssh/sshd_config
sed -i 's/PasswordAuthentication yes/PasswordAuthentication no/g' /etc/ssh/sshd_config
  1. Only allow login from selected users
echo "AllowUsers $username" >> /etc/ssh/sshd_config
  1. Restart ssh server
service ssh restart

Firewall & fail2ban

  1. Setup ufw (Ubuntu Firewall)
    # ufw (Ubuntu Firewall)
    ufw default deny incoming
    ufw default allow outgoing

    # Open SSH
    ufw allow ssh

    # Open web ports
    ufw allow 443/tcp
    ufw allow 80/tcp

    # Enable firewall and fail2ban
    ufw --force enable
  1. Setup fail2ban

apt-get install -y fail2ban

  1. Confirm status
    [email protected]:~# ufw status
    Status: active

    To                         Action      From
    --                         ------      ----
    22                         ALLOW       Anywhere
    443/tcp                    ALLOW       Anywhere
    80/tcp                     ALLOW       Anywhere
    22 (v6)                    ALLOW       Anywhere (v6)
    443/tcp (v6)               ALLOW       Anywhere (v6)
    80/tcp (v6)                ALLOW       Anywhere (v6)

    [email protected]:~# service fail2ban status
     * Status of authentication failure monitor
     *  fail2ban is running
  1. Ensure you can connect from a new terminal window before disconnecting
    $ ssh [email protected]_IP

Updating & Upgrading

  1. Set the time zone to your choice

    NOTE: I had to run $ tzconfig before the above command would work for me.

    $ dpkg-reconfigureĀ tzdata
  1. Update server to latest software

    apt-get update will fetch all the latest updates.
    apt-get upgrade will apply updates.

    $ apt-get update && apt-get upgrade -y
    ...
    # Make sure you are able to reconnect from a new window before this step
    $ shutdown -r now

Software Installation

Basic utilities to install

sudo apt-get install -y htop zsh tree git vim nginx nodejs make npm cmake python-dev
  • htop - processor monitor
  • tree - tree view directories
  • git - the stupid content tracker
  • vim - text editor
  • nginx - web server / reverse proxy
  • make - build tools
  • cmake - more build tools
  • python-dev - even more building tools

Configuration & Debugging

  • nginx - sudo vim /etc/nginx/sites-enabled/default
    sudo service nginx restart

  • ssh - sudo vim /etc/ssh/sshd_config
    sudo service ssh restart

  • logs/var/log
    sudo tail -f /var/log/nginx/access.log

Shell Scripting

#!/bin/bash

# This is a comment
echo "Hello World"

# make script executable
chmod a+x hello.sh

# execute script
./hello.sh

Git remote repository

On the remote machine

$ mkdir ~/web-project-name.git
$ git init --bare ~/web-project-name.git

From local machine

$ cd ~/projects/web-project
$ git remote add web-hostname [email protected]_IP:web-project-name.git
$ git push web-hostname master
  • Githooks
    • post-update for deployment

Challenge: Setup the git post-update hook to deploy website

Gotchas

  • ctrl + z by accident?
    • fg to foreground the application

NodeJS with Nginx

  • Add a site config to /etc/nginx/sites-available/site.conf.
  • Soft link ln -s /etc/nginx/sites-available/site.conf /etc/nginx/sites-enabled/ to enable the site.
  • sudo service nginx reload to apply the changes.
  • Change the port number from 3000 to whatever your node app is running on.

Next time

  • Automation
    • Ansible
  • PaaS
  • Docker
  • Dokku

Future talk ideas

  • Nginx Setup with NodeJS
  • DNS
  • Monitoring
  • Automation deep dive
  • AWS
    • Basics
    • Security Groups
    • EC2
    • Load Balancing
    • etc…
  • Continuous Integration
Author Avatar

Matt Carrier

I am a pixel connoisseur who enjoys the finer details of a Bresenham line. When not staring at arrays of smoothly rendered pixels I enjoy playing guitar and consuming coffee.