Bash script to automate an arch install for virtual machines

Arch VM Install Script

#!/bin/bash

DISK=""
USERNAME="user"
PASSWORD="pass"

btrfs_setup()
{
    subvols=(
        ""
        "home"
    )

    paths=(
        "/"
        "/home"
    )

    # Mount the Root Partition
    mount "${DISK}3" /mnt

    # Create Ubuntu-style Btrfs Subvolumes
    pushd /mnt

    for index in ${!subvols[*]}; do 
        btrfs subvolume create @"${subvols[$index]}"
        btrfs quota enable @"${subvols[$index]}"
        mkdir -p @"${paths[$index]}"
    done

    mkdir -p @/boot
    popd

    # Unmount the Root and Boot Partitions
    umount /mnt

    # Remount the Root Partition with Subvolumes
    for index in ${!subvols[*]}; do 
        mount -o compress=lzo,ssd,noatime,nodiratime,space_cache,discard,subvol=@"${subvols[$index]}" \
            "${DISK}3" "/mnt${paths[$index]}"
    done

    mount "${DISK}1" /mnt/boot
}

partition_disk()
{
    (
	    printf "o\n" # Set DOS Type
	    printf "n\n" # New Partition
	    printf "p\n" # Primary Partition
	    printf "1\n" # Partition 1 - Boot
	    printf " \n" # From First Sector
	    printf "+512M\n" # 512MB Boot Partition
	    printf "n\n" # New Partition
	    printf "p\n" # Primary Partition
	    printf "2\n" # Partition 2 - Swap
	    printf " \n" # From Next Sector
	    printf "+2G\n" # 2GB Swap Partition
	    printf "n\n" # New Partition
	    printf "p\n" # Primary Partition
	    printf "3\n" # Partition 3 - Root
	    printf " \n" # From Next Sector
	    printf " \n"   # NGB Root Partition
	    printf "a\n" # Set Bootable Flag
	    printf "1\n" # Partition 1 - Bootable
	    printf "w\n" # Write Changes to Disk
    ) | sudo fdisk "${DISK}"

    # Format the Boot Partition
    mkfs.ext4 "${DISK}1"

    # Format the Swap Partition
    mkswap "${DISK}2"

    # Enable the Swap Partition
    swapon "${DISK}2"

    # Format the Root Partition
    mkfs.btrfs -L root "${DISK}3"
}

prompt_disk()
{
    fdisk -l
    echo -e "\n\nEnter your disk (/dev/sda): "
    while read DISK; do
        if [ ! -b "${DISK}" ]; then
            echo "Invalid disk: ${DISK}."
            continue
        else
            break
        fi
    done
}

timedatectl set-ntp true

prompt_disk
partition_disk
btrfs_setup

pacstrap /mnt base base-devel linux linux-firmware
genfstab -U /mnt >> /mnt/etc/fstab

cat << EOF > /mnt/root/stage2.sh
DISK="${DISK}"

localization()
{
    # Set Time Zone
    ln -sf "/usr/share/zoneinfo/\${1}/\${2}" /etc/localtime
    hwclock --systohc

    # Set Locale
    echo "LANG=en_US.UTF-8" >> /etc/locale.conf
    sed -i '/^#en_US.UTF-8/s/^#//' /etc/locale.gen
    locale-gen
}

setup_bootloader()
{
    pacman -S grub os-prober --noconfirm
    grub-install --target=i386-pc "${DISK}"
    grub-mkconfig -o /boot/grub/grub.cfg
}

intel_microcode()
{
    if grep "Intel" /proc/cpuinfo; then
	    pacman -S intel-ucode --noconfirm
    fi
}

# Arg1 is the username for the new user
# Arg2 is the password for the new user
add_user()
{
    useradd -m -G wheel -s /bin/bash "\${1}"
    echo "\${1}:\${2}" | chpasswd
}

enable_wheel()
{
    sed -i '0,/^# %wheel/ s/^# //' /etc/sudoers
}

setup_de()
{
    # Install Gnome
    pacman -S gnome gnome-tweaks --noconfirm

    # Enable GDM
    systemctl enable gdm

    # Enable NetworkManager
    systemctl enable NetworkManager

    # Set Graphical Option
    systemctl set-default graphical.target
}

setup_snapshotting()
{
    pacman -S snap-pac --noconfirm
    # AFAIK, this has to be run after reboot to avoid "Failure (org.freedesktop.DBus.Error.ServiceUnknown)"
    # snapper -c root create-config /
}

sed -i 's/fsck/btrfs/g' /etc/mkinitcpio.conf

localization "America" "Chicago"

echo "dev" > /etc/hostname

intel_microcode

setup_bootloader

enable_wheel
add_user "${USERNAME}" "${PASSWORD}"

setup_de

setup_snapshotting

rm /root/stage2.sh
EOF

chmod +x /mnt/root/stage2.sh
arch-chroot /mnt /root/stage2.sh
umount -R /mnt