How to Overlay two files with UnionFs in a Linux System


UnionFS creates a unified seamless filesystem by transparently overlaying files and directories from separate filesystems. Each participant directory is referred to as a branch, and when mounting branches, we can set priorities and access modes. In this short guide, we shall be looking at how to get it installed in Ubuntu 22.04. Other guides can be accessed from here: How To Install Nextcloud on a Linux system and How to install Gradle on Ubuntu and How to Install Apache OpenOffice on Ubuntu  and How to Install MongoDB on a Linux System and How to install Node.js on Ubuntu

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  • A Linux Machine (Ubuntu 18 or Higher)
  • A user account with sudo privileges

Step1: Update the package index

you can use the command below :

apt-get update

Step2: install Unionfs

you can use the command below:

sudo apt install -y unionfs-fuse

Step3: create two separate directories (branches) with two files each respectively

mkdir dir1
touch dir1/f1
touch dir1/f2
mkdir dir2
touch dir2/f3
touch dir2/f4
directories and files

Step4: Let’s create an empty directory

This directory is where union will be mounted and we can do this with the command as shown below:

mkdir union
dir union

Step 5: Mount the two branches

we can overlay the two branches on top of each with the command :

unionfs dir1/:dir2/ union/

Step6: verify the files

we can do this with the command :

ls union/


We can use Unionfs to over several files by following the steps as shown above

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