Basic list of commands to setup new server instance. (Tested only for Ubuntu 12.04) (Taken from digitalocean tutorials.)

linux-server-setup.sh

# A small set of commands to do basic server setup
# First and foremost add password to root
sudo passwd root

# Update the dist
sudo apt-get update && sudo apt-get upgrade

# Block rogue connections by
# allowing only ssh, port - 80, 443
# using Uncomplicated Firewall (ufw)
sudo ufw allow ssh
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp

# Verify the ufw rules added
sudo ufw show added

# Enable the firewall
sudo ufw enable

# Configure server timezone
sudo dpkg-reconfigure tzdata

# Configure local ntp (Network Time Protocol)
sudo apt-get install ntp

# Allocate space for swap
sudo fallocate -l 7G /swapfile

# Change permissions on swapfile
sudo chmod 600 /swapfile

# Make swap
sudo mkswap /swapfile
sudo swapon /swapfile
sudo sh -c 'echo "/swapfile none swap sw 0 0" >> /etc/fstab'

# Create group for working
groupadd groupname

# Add a new user to group
useradd -g groupname username

# Set passwd for user
passwd username

# Check the passwd file for newly created user
# verify its similar to ->
# username:x:1000:1000::/home/username:/bin/bash
# also verify /bin/bash is not /bin/sh
vim /etc/passwd

# Change sudo permissions
# Should be similar to ->
#
# - User privilege specification
# root    ALL=(ALL:ALL) ALL
#
# - Members of the admin group may gain root privileges
# %admin ALL=(ALL) ALL
#
# - Allow members of group sudo to execute any command
# %sudo   ALL=(ALL:ALL) ALL
#
# - <groupname> permissions
# %groupname ALL=(ALL:ALL) ALL
#
# - See sudoers(5) for more information on "#include" directives:
# - includedir /etc/sudoers.
visudo

# Install nginx for running app servers
sudo apt-get install nginx

# Change your user
su username

# Check if /home has directory /username if not run following
cd /home && sudo mkdir username && sudo chown username:groupname username && cd ~

# Enable ssh login to user account
mkdir .ssh && vim .ssh/authorized_keys

# Give correct permissions to authorized_keys
# otherwise ssh login wont work for keys
chmod 600 .ssh/authorized_keys
chmod 700 .ssh

# Change ssh config to prevent
# password and root login
#
# Change file values to following
# PermitRootLogin no
# PasswordAuthentication no
vim /etc/ssh/sshd_config

# Restart the service
sudo service ssh restart

# Disable root account
sudo passwd -l root