setupLibrary.sh

#!/bin/bash

# Function to read options 
# Arguments: options.txt file location
function read_options {
  # Declare variables with global scope
  declare -g username="user1"
  declare -g timezone="Europe/Berlin"
  declare -g public_key_file="settings/local.pub"
  declare -g docker_enabled="no"

  # Check if the file exists
  if [[ ! -f $1 ]]; then
    echo "Error: $1 file not found! moving forward with default settings."
    #return with default options
    return
  fi

  # Read the file line by line
  while read -r line; do
    # Extract the keyword and value from each line
    keyword=$(echo "$line" | awk '{print $1}')
    value=$(echo "$line" | awk '{print $2}')

    # Process each line based on the keyword
    case "$keyword" in
      "uname")
        username="$value"
        ;;
      "tzone")
        timezone="$value"
        ;;
      "pubkey")
        public_key_file="$value"
        ;;
      "docker")
        docker_enabled="$value"
        ;;
      *)
        echo "Warning: Unrecognized keyword \"$keyword\" in " $1
        ;;
    esac
  done <$1
}

# Function to install Docker
function install_docker {
  # Install required dependencies to add a repository over HTTPS
  sudo apt install --assume-yes apt-transport-https ca-certificates curl software-properties-common

  # Add Docker's official GPG key
  curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

  # Add Docker repository
  echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list

  # Update package lists (again after adding Docker repository)
  sudo apt update --assume-yes

  # Install Docker
  sudo apt install --assume-yes docker-ce

  # Start and enable Docker service
  sudo systemctl start docker
  sudo systemctl enable docker

  # Add the current user to the "docker" group to use Docker without sudo
  sudo usermod -aG docker "$USER"

  # Display Docker version as a verification step
  docker version
}




# Update the user account
# Arguments:
#   Account Username
function updateUserAccount() {
    local username=${1}
    
    sudo passwd -d "${username}"
    sudo usermod -aG sudo "${username}"
}

# Add the new user account
# Arguments:
#   Account Username
#   Flag to determine if user account is added silently. (With / Without GECOS prompt)
function addUserAccount() {
    local username=${1}
    local silent_mode=${2}

    if [[ ${silent_mode} == "true" ]]; then
        sudo adduser --disabled-password --gecos '' "${username}"
    else
        sudo adduser --disabled-password "${username}"
    fi

    sudo usermod -aG sudo "${username}"
    sudo passwd -d "${username}"
}

# Add the local machine public SSH Key for the new user account
# Arguments:
#   Account Username
#   Public SSH Key
function addSSHKey() {
    local username=${1}
    local sshKey=${2}

    execAsUser "${username}" "mkdir -p ~/.ssh; chmod 700 ~/.ssh; touch ~/.ssh/authorized_keys"
    execAsUser "${username}" "echo \"${sshKey}\" | sudo tee -a ~/.ssh/authorized_keys"
    execAsUser "${username}" "chmod 600 ~/.ssh/authorized_keys"
}

# Execute a command as a certain user
# Arguments:
#   Account Username
#   Command to be executed
function execAsUser() {
    local username=${1}
    local exec_command=${2}

    sudo -u "${username}" -H bash -c "${exec_command}"
}

# Modify the sshd_config file
# shellcheck disable=2116
function changeSSHConfig() {
    sudo sed -re 's/^(\#?)(PasswordAuthentication)([[:space:]]+)yes/\2\3no/' -i."$(echo 'old')" /etc/ssh/sshd_config
    sudo sed -re 's/^(\#?)(PermitRootLogin)([[:space:]]+)(.*)/PermitRootLogin no/' -i /etc/ssh/sshd_config
}

# Setup the Uncomplicated Firewall
function setupUfw() {
    sudo apt-get --assume-yes install ufw
    sudo ufw allow OpenSSH
    yes y | sudo ufw enable
}

# Create the swap file based on amount of physical memory on machine (Maximum size of swap is 4GB)
function createSwap() {
   local swapmem=$(($(getPhysicalMemory) * 2))

   # Anything over 4GB in swap is probably unnecessary as a RAM fallback
   if [ ${swapmem} -gt 4 ]; then
        swapmem=4
   fi

   sudo fallocate -l "${swapmem}G" /swapfile
   sudo chmod 600 /swapfile
   sudo mkswap /swapfile
   sudo swapon /swapfile
}

# Mount the swapfile
function mountSwap() {
    sudo cp /etc/fstab /etc/fstab.bak
    echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
}

# Modify the swapfile settings
# Arguments:
#   new vm.swappiness value
#   new vm.vfs_cache_pressure value
function tweakSwapSettings() {
    local swappiness=${1}
    local vfs_cache_pressure=${2}

    sudo sysctl vm.swappiness="${swappiness}"
    sudo sysctl vm.vfs_cache_pressure="${vfs_cache_pressure}"
}

# Save the modified swap settings
# Arguments:
#   new vm.swappiness value
#   new vm.vfs_cache_pressure value
function saveSwapSettings() {
    local swappiness=${1}
    local vfs_cache_pressure=${2}

    echo "vm.swappiness=${swappiness}" | sudo tee -a /etc/sysctl.conf
    echo "vm.vfs_cache_pressure=${vfs_cache_pressure}" | sudo tee -a /etc/sysctl.conf
}

# Set the machine's timezone
# Arguments:
#   tz data timezone
function setTimezone() {
    local timezone=${1}
    echo "${1}" | sudo tee /etc/timezone
    sudo ln -fs "/usr/share/zoneinfo/${timezone}" /etc/localtime # https://bugs.launchpad.net/ubuntu/+source/tzdata/+bug/1554806
    sudo dpkg-reconfigure -f noninteractive tzdata
}

# Configure Network Time Protocol
function configureNTP() {
    ubuntu_version="$(lsb_release -sr)"

    if [[ $(bc -l <<< "${ubuntu_version} >= 20.04") -eq 1 ]]; then
        sudo systemctl restart systemd-timesyncd
    else
        sudo apt-get --assume-yes update
        sudo apt-get --assume-yes install ntp
        
        # force NTP to sync
        sudo service ntp stop
        sudo ntpd -gq
        sudo service ntp start
    fi
}

# Gets the amount of physical memory in GB (rounded up) installed on the machine
function getPhysicalMemory() {
    local phymem
    phymem="$(free -g|awk '/^Mem:/{print $2}')"
    
    if [[ ${phymem} == '0' ]]; then
        echo 1
    else
        echo "${phymem}"
    fi
}

# Disables the sudo password prompt for a user account by editing /etc/sudoers
# Arguments:
#   Account username
function disableSudoPassword() {
    local username="${1}"

    sudo cp /etc/sudoers /etc/sudoers.bak
    sudo bash -c "echo '${1} ALL=(ALL) NOPASSWD: ALL' | (EDITOR='tee -a' visudo)"
}

# Reverts the original /etc/sudoers file before this script is ran
function revertSudoers() {
    sudo cp /etc/sudoers.bak /etc/sudoers
    sudo rm -rf /etc/sudoers.bak
}