Remove all console messages on Raspberry Pi

gistfile1.txt

#!/bin/bash

if [[ ! $UID -eq 0 ]]; then
    echo "you must run this as root:"
    echo "sudo $0"
    exit 1
fi

touch /home/pi/.hushlogin

# Make backups if first time running
if [ ! -f /etc/rc.local-backup ]; then
    cp -a /etc/rc.local /etc/rc.local-backup
    echo -e "\e[91mcreated backup of /etc/rc.local\e[30m"
fi

if [ ! -f /etc/issue-backup ]; then
    cp -a /etc/issue /etc/issue-backup
    echo -e "\e[91mcreated backup of /etc/issue\e[30m"
fi

if [ ! -f /boot/cmdline-backup.txt ]; then
    cp -a /boot/cmdline.txt /boot/cmdline-backup.txt
    echo -e "\e[91mcreated backup of /boot/cmdline.txt\e[30m"
fi

if [ ! -f /etc/systemd/system/autologin\@-backup.service ]; then
    cp -a /etc/systemd/system/autologin\@.service /etc/systemd/system/autologin\@-backup.service
    echo -e "\e[91mcreated backup of /etc/systemd/system/autologin\@.service\e[30m"
fi

if [ ! -f /etc/pam.d/login-backup ]; then
    cp -a /etc/pam.d/login /etc/pam.d/login-backup
    echo -e "\e[91mcreated backup of /etc/pam.d/login\e[30m"
fi

# Change /boot/cmdline.txt: replace tty1 with tty3 and add arguments
sed -i 's/console=tty1/console=tty3/g' "/boot/cmdline.txt"
if !(grep -q "quiet splash loglevel=0 logo.nologo" "/boot/cmdline.txt";) then
    sed -i -e :a -e '/^\n*$/{$d;N;};/\n$/ba' /boot/cmdline.txt # Delete all trailing blank lines at end of file (only). And save with -i
    sed -i '${s/$/ quiet splash loglevel=0 logo.nologo vt.global_cursor_default=0 plymouth.ignore-serial-consoles/}' "/boot/cmdline.txt"
fi
echo -e "\e[91mOUTPUT of /boot/cmdline.txt:\e[30m"
cat /boot/cmdline.txt

# Change ExecStart on /etc/systemd/system/autologin@.service
if !(grep -q "\-\-skip-login" "/etc/systemd/system/autologin@.service";) then
    sed -i 's/ExecStart=-\/sbin\/agetty --autologin pi --noclear %I $TERM/ExecStart=-\/sbin\/agetty --skip-login --noclear --noissue --login-options \"-f pi\" %I $TERM/g' "/etc/systemd/system/autologin@.service"
fi
echo -e "\e[91mOUTPUT of /etc/systemd/system/autologin\@.service:\e[30m"
cat /etc/systemd/system/autologin\@.service

# Tell dmesg to be quiet in /etc/rc.local
if grep -q "dmesg --console-off" "/etc/rc.local"; then
    echo -e "\e[91malready inserted dmesg --console-off in /etc/rc.local\e[30m"
else
    echo "insert dmesg --console-off"
    sed -i "/exit 0/ i #Suppress Kernel Messages\ndmesg --console-off" "/etc/rc.local"
fi
echo -e "\e[91mOUTPUT of /etc/rc.local:\e[30m"
cat /etc/rc.local

# Remove entire content of file /etc/issue
sed -i d /etc/issue
echo -e "\e[91mOUTPUT of /etc/issue:\e[30m"
cat /etc/issue

# Change ExecStart on /etc/pam.d/login
if grep -q "pam_exec.so type=open_session stdout \/bin\/uname -snrvm" "/etc/pam.d/login"; then
    sed -i 's/pam_exec.so type=open_session stdout \/bin\/uname -snrvm/session optional pam_exec.so type=open_session stdout/g' "/etc/pam.d/login"
fi
echo -e "\e[91mOUTPUT of /etc/pam.d/login:\e[30m"
cat /etc/pam.d/login

# Change prompt to $ in the console by editing ~/.bashrc
# Word of warning if you intend to show no prompt indicator: 
# consoles without any indicators can be a bit confusing mid-development.
if !(grep -q "PS1=\"$\"" "/home/pi/.bashrc";) then
    sed -i '${s/$/\nPS1="$"/}' "/home/pi/.bashrc"
fi
echo -e "\e[91mOUTPUT of ~/.bashrc:\e[30m"
cat /home/pi/.bashrc