Ubuntu-Debian APT upgrade script

system_update.sh

#!/bin/bash
#
# Brady Shea - 18SEP2020 - conversion of system_update alias to bash script
# https://www.holylinux.net/
#
# Place this script in "/usr/local/sbin/system_update" or similar location under your $PATH
# It needs root permissions (SUDO) to execute.
#
# Change these settings to your liking:
#################################
noprompting=true                # ( true | false ) (APT option:  -y, --yes, --assume-yes)
sleepy=5                        # Pause a bit between autoremoves and updates
bootpartitionwarning=102400     # 102400 1kb blocks (~100MiB) is a reasonable amount
#################################

# STATIC VARIABLES #
BRIGHT_RED=$(tput bold)$(tput setaf 1)
BRIGHT_GREEN=$(tput bold)$(tput setaf 2)
GREEN=$(tput setaf 2)
BRIGHT_YELLOW=$(tput bold)$(tput setaf 3)
BRIGHT_WHITE=$(tput bold)$(tput setaf 7)
COLOR_OFF=$(tput sgr0)
scriptname=`basename "$0"`
rebootfileflag=/var/run/reboot-required

# OTHER VARIABLES #
noprompt=
if [[ $noprompting == "true" ]]; then
  noprompt=-y
fi
rebootreq=0
bootavail=0
problems=0

# FUNCTIONS #
root_user () { [ ${EUID:-$(id -u)} -eq 0 ]; }
## No point going any further in script if not sudo:
if ! root_user; then printf "\nPlease use: \'sudo ${scriptname}\'\nExiting.\n\n"; exit; fi

sleeptimer () {
  for (( count=1; count<=$sleepy; count++ )); do
    printf "${BRIGHT_WHITE}.${COLOR_OFF}"; sleep 1;
  done
  printf "\n"
}

rebootcheck () {
  rebootreq="false"
  if [ -f $rebootfileflag ]; then
    rebootreq="true"
  fi
}

okaynookay () {
  showalert="${GREEN}(PASS)${COLOR_OFF}"
  if [ $problems == "1" ]; then
    showalert="${BRIGHT_RED}(FAIL)${COLOR_OFF}"
  fi
  problems=0
}

# MAIN PROGRAM #
printf "\n${BRIGHT_YELLOW}SYSTEM UPDATE STARTED${COLOR_OFF}\n\n"

printf " ${BRIGHT_WHITE}Current Distribution:${COLOR_OFF} %b %b %b\n" $(lsb_release -sd)

bootavail=$(df --output=avail /boot | tail -n 1)
if [[ $bootavail -lt bootpartitionwarning ]]; then
  problems=1; okaynookay
  displaybootavail="${bootavail} ${showalert}"
else
  problems=0; okaynookay
  displaybootavail="${bootavail} ${showalert}"
fi
printf " ${BRIGHT_WHITE}Available /boot space:${COLOR_OFF} %s %s\n" $displaybootavail

rebootcheck ## (pre update)
if [[ $rebootreq == "true" ]]; then
  problems=1; okaynookay;
  displayrebootreq="${rebootreq} ${showalert}"
else
  problems=0; okaynookay;
  displayrebootreq="${rebootreq} ${showalert}"
fi
printf " ${BRIGHT_WHITE}Reboot required currently:${COLOR_OFF} %s %s\n" $displayrebootreq

if [[ $rebootreq == "true" || $bootavail -lt $bootpartitionwarning ]]; then
  while true; do
    read -p " $(echo -e "You have warnings. Proceed anyway? [y/N] ")" userinput
    case $userinput in
      [Yy]* ) break;;
      [Nn]* ) exit;;
      * ) exit;;
    esac
  done
fi

# START UPDATE #

printf "\n${BRIGHT_WHITE}Updating from sources..${COLOR_OFF}\n"
apt update

printf "\n${BRIGHT_WHITE}Running autoremove before updates..${COLOR_OFF}\n"
apt ${noprompt} autoremove

printf "\n${BRIGHT_WHITE}Autoremove completed. Sleeping ${sleepy} seconds${COLOR_OFF}"; sleeptimer

printf "\n${BRIGHT_WHITE}Installing any upgrades found..${COLOR_OFF}\n"
apt ${noprompt} upgrade

printf "\n${BRIGHT_WHITE}Updates have completed. Sleeping ${sleepy} seconds${COLOR_OFF}"; sleeptimer

printf "\n${BRIGHT_WHITE}Updating from sources..${COLOR_OFF}\n"
apt update

printf "\n${BRIGHT_WHITE}Re-running autoremove post-updates..${COLOR_OFF}\n"
apt ${noprompt} autoremove

rebootcheck ## (post update)
if [[ $rebootreq == "true" ]]; then
    printf "\n${BRIGHT_RED} *** A system reboot is required. ***${COLOR_OFF}\n"
else
    printf "\n${GREEN} A system reboot is NOT required at this time.${COLOR_OFF}\n"
fi
printf "\n${BRIGHT_YELLOW}SYSTEM UPDATE COMPLETED. Exiting.${COLOR_OFF}\n\n"

A 'clean' way to do apt updates on debian/ubuntu/etc.. with autoremove.
I have used something similar to this for years and have never had a problem with updates/upgrades.

USE

Place this script in /usr/local/sbin/system_update (or similar location under your $PATH)
It needs root permissions (SUDO) to execute.

I have added a sudo check, a reboot check (pre and post update) and a /boot space check as well (Updated 19JUN2021):

Failure(s) will look like this:

A failure is either low /boot space, or a reboot is needed (less than 100MiB default - see bootpartitionwarning in adjustable variables).
These should probably be corrected before proceeding. You can of course continue the update, but you were warned.