Runar Ovesen Hjerpbakk

Programmer. Software Architect. Technical Manager.

Automatically update and upgrade Raspbian

Continuing the theme of last night, today I improved the upgrade experience of my Raspberry Pi.

Manual upgrade

As per the documentation, update and upgrade are as easy as running these two commands. First update your system’s package list:

sudo apt -y update

Then upgrade all installed packages to their latest version:

sudo apt -y dist-upgrade

I use -y to answer yes to all prompts by default. Easy enough, but in our modern DevOpsy world, we need to automate this.

Automation to the rescue

I created a simple script in bash which creates these two commands as scheduled tasks using Cron. The image below shows my output of crontab -l:

crontab -l

Let’s go through the update command from the script as an educational example :

if crontab -l | grep -q "sudo apt -y update"; 
then 
  echo "Auto update of package list already exists in crontab"
else
  echo "Adding auto update of package list to crontab"
  (crontab -l 2>/dev/null; echo "0 3 * * * sudo apt -y update"); echo | crontab - 
fi
  • First we check if this command already exist in crontab. This StackOverflow answer helped me here.
  • If it does, our work is already done. Idempotent scripts are something to strive for, and this achieves it. We can run this script again and again with the same result.
  • If crontab lacks our entry, we add it. The first 2>/dev/null is there so that we don’t get the no crontab for username message if there are currently no crontab entries. Then we create our entry making the update command run every night at 03:00. Lastly, we pipet this to crontab using standard out.
  • I did the same for the upgrade command, just made it run an hour later so that update always completes first. To understand the cron patterns for when the task should run, see my post from yesterday.

Thus this script can be run anytime and the end result is that crontab runs both of these commands nightly.

The script can be downloaded and run directly on your Raspberry Pi, remember chmod +x, or it can be run straight from GitHub using curl:

$ curl -s https://raw.githubusercontent.com/Sankra/dotfiles/master/tasks/auto-update | sudo sh

Just remember to never run scripts of the Internet before first understanding them!

The entire script looks like this:

#!/bin/bash
set -e

echo "Installing automatic updates..."

if crontab -l | grep -q "sudo apt -y update"; 
then 
  echo "Auto update of package list already exists in crontab"
else
  echo "Adding auto update of package list to crontab"
  (crontab -l || true; echo "0 3 * * * sudo apt -y update") | crontab - 
fi

if crontab -l | grep -q "sudo apt -y dist-upgrade"; 
then 
  echo "Upgrade of installed packages already exists in crontab"
else
  echo "Adding upgrade of installed packages"
  (crontab -l || true; echo "0 4 * * * sudo apt -y upgrade") | crontab - 
fi

echo "Installation complete. Enjoy!"