Numix is one of the most beautiful themes set for Linux desktop. It was
initially created in 2013-14 and since then, it’s become a host favorite among Linux users. There have been many new beautiful icon themes for
Linux lately but Numix remains an evergreen hit. Its flat approach gives a fresh look to your desktop. This was the reason why several Linux distributions used to ship with Numix as the default theme. Unlike Ubuntu, there is no Personal Package Archives (PPA) repository for Numix theme and icons in Debian instead we can install it via Git
Step 1: Install Git
sudo apt update
If it shows unmet dependencies execute this
apt --fix-broken install
sudo apt install git
Step 2: Create a Directory called Numix
mkdir numix
Step 3: Change into Numix directory
cd numix
Step 4: Clone numix theme, icons execute this one by one
git clone https://github.com/cldx/numix-gtk-theme
git clone https://github.com/numixproject/numix-icon-theme
git clone https://github.com/numixproject/numix-icon-theme-circle
Step 4: Open hidden directories in the home
Please make sure there are directories called .icons .themes if no, create those
mkdir .icons .themes
Step 5: Move Numix-Circle, Numix-Circle-Light and Numix directories from numix/numix-icon-theme-circle and numix-icon-theme respectively into the .icons directory as non-root user
sudo mv numix/numix-icon-theme-circle/Numix-Circle/ /home/mahesh/.icons
sudo mv numix/numix-icon-theme-circle/Numix-Circle-Light/ /home/mahesh/.icons
sudo mv numix/numix-icon-theme/Numix/ /home/mahesh/.icons
Step 6: Move numix-gtk-theme from numix into the .themes directory
sudo mv numix/numix-gtk-theme/ /home/mahesh/.themes
sudo mv numix/numix-gtk-theme/ /home/mahesh/.themes
Step 7: Install Unity-Tweak-Tool if not,
sudo apt-get install unity-tweak-tool
Reference: https://www.youtube.com/watch?v=1G4XGNHMpNM