Synology: How to Free Disk Space on Your NAS if You Run Docker

Synology How to Free Disk Space on Your NAS if You Run Docker

Today I happened to notice that my Synology NAS was using up more disk space than it should have. I didn’t understand right away why this was happening, but then I remembered that over the last few months I had installed several images for Docker for various containers. The funny thing is that “junk” images are not displayed in the graphical interface of the Docker package. So everything seemed in order. It then came to me that over the last year I have been using Watchtower to do automatic updates of all my docker containers. Surely it was an oversight on my part that I had never noticed that so many old container images were saved on my NAS, but not visible in the Docker interface itself.

1 Clean Space Synology disks Docker Portainer

Thanks to Portainer, I was able to locate the junk images and delete them from my Synology NAS. And it was extremely easy. I managed to free a whopping 24.5 GB of space on my SSD drives and went from 132 GB to 107.5 GB. Below I will explain how I did it so you can do it yourself too.

  • STEP 1

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  • STEP 2

Install Portainer on your Synology NAS using my Step by Step Guide. Note: If you already have Portainer installed, skip this STEP.

  • STEP 3

Open Portainer then locate the text “Images” in the menu on the left. Click on “Images“. You will see so many “Unused” images labeled as such against an orange background. So select all the Unused images, then click Remove. The removal process will start instantly and it can take a few minutes depending on how many unused images you have. Note: Remember to select only the images labeled Unused in the orange background. The ones that aren’t labeled as “Unused” are perfectly working images belonging to the containers you are currently running. Follow the instructions in the image below.

3 Clean Space Synology disks Docker Portainer

  • STEP 4

Go back to STEP 1 or you will deal with karma 🙂

  • STEP 5

Go check how much space you have cleared. I have freed up  24.5 GB of space which is Whoa!

2 Clean Space Synology disks Docker Portainer

Note: Portainer becomes a must have if you have Docker installed on your Synology NAS.
Note: To avoid this issue with old container images, you should install Watchtower using my step by step guide.

This post was updated on Friday / January 8th, 2021 at 8:50 PM