parrot.sh

#!/bin/bash

if [[ "$EUID" -ne 0 ]]; then
    echo "ERROR: Please run this script as root." >&2
    exit 1
fi

export DEBIAN_FRONTEND=noninteractive
export DEBCONF_NONINTERACTIVE_SEEN=true
# Get latest metadata from mirrors.
apt update

# Install the prefered display manager for KDE.
apt install -y sddm

# Normally it would interactively prompt you via an ncurses ui to select the default display manager... but this is a script.
echo "/usr/bin/sddm" > /etc/X11/default-display-manager
dpkg-reconfigure sddm
echo "set shared/default-x-display-manager sddm" | debconf-communicate

# Install the KDE meta package for Parrot OS, and the KDE Config Module for SDDM.
apt install -y parrot-kde kde-config-sddm
# Remove the MATE metapackage.
apt purge -y --auto-remove mate-desktop

# Automatic login
mkdir -p /etc/sddm.conf.d
cat <<- "EOF" >/etc/sddm.conf.d/autologin.conf
[Autologin]
User=user
Session=plasma
EOF

# Test if we're running inside a KVM/QEMU VM. If so, install the appropriate guest stuff.
if dmidecode | grep -q "Manufacturer: QEMU"; then
    # Get the spice and QEMU guest stuff.
    apt install -y spice-vdagent qemu-guest-agent
    # Remove the Virtualbox guest stuff.
    apt purge -y virtualbox-guest-x11 virtualbox-guest-utils

    # Auto-resizing doesn't work at the moment, without giving it a little push.
    # The VM window (spice) resize event is seen by udev, so register a script that needs to run when it happens.
    # REMEMBER TO ENABLE AUTO-RESIZE IN VIRT-MANAGER: VIEW-> SCALE DISPLAY -> AUTO RESIZE VM WITH WINDOW
    echo 'ACTION=="change", KERNEL=="card0", SUBSYSTEM=="drm", RUN+="/usr/local/bin/x-resize"' > /etc/udev/rules.d/50-x-resize.rules
    # Create the script that tells xrandr to do the right thing.
    cat <<- "EOF" >/usr/local/bin/x-resize
#!/bin/sh
PATH=/usr/bin
desktopuser=$(/bin/ps -ef  | /bin/grep -oP '^\w+ (?=.*vdagent( |$))') || exit 0
export DISPLAY=:0
export XAUTHORITY=$(eval echo "~$desktopuser")/.Xauthority
xrandr --output $(xrandr | awk '/ connected/{print $1; exit; }') --auto
EOF
    # Make the script executable.
    chmod +x /usr/local/bin/x-resize
fi

# Install latest things.
apt dist-upgrade -y
# Remove unwanted things.
apt autoremove -y

# Clean up default junk from the desktop.
rm -f /home/user/Desktop/{PASSWORD.txt,README.license}