Almost forgot ImageMagik
Rails 5.2 now has ActiveStorage which is amazing. However if you want to use some of the built in image processing tools, you have to have ImageMagick installed on all computers running your site (development laptops, production servers, etc.).
Welp, I deployed this site and almost forgot to install ImageMagik. Since I'm here, I thought I'd quickly write down the steps as a future reference:
System: Ubuntu 18.04
Version: ImageMagick 7.x
cd sudo apt-get install build-essential checkinstall && sudo apt-get build-dep imagemagick -y sudo wget http://www.imagemagick.org/download/ImageMagick.tar.gz sudo tar xzvf ImageMagick.tar.gz cd ImageMagick-7* sudo ./configure sudo make clean sudo make sudo checkinstall sudo ldconfig /usr/local/lib
Check if everything worked: