`sudo service docker start` can result in error "Failed to start docker.service: Unit docker.service not found."

[peterzahemszky]

When following the README.rst document, the sudo service docker start command fails with the following error:

Failed to start docker.service: Unit docker.service not found.

Docker version 20.10.8 (installed via Snap)
Operating system: Kubuntu 18.04

[peterzahemszky]

For the record, running docker info prints the following error message:

Client:
 Context:    default
 Debug Mode: false

Server:
ERROR: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/info": dial unix /var/run/docker.sock: connect: permission denied
errors pretty printing info

Then if I run sudo usermod -a -G docker $USER as suggested by this comment on Stack Overflow, I get the following error:

usermod: group 'docker' does not exist

Running sudo docker info does not trigger the error message above.

[peterzahemszky]

I followed the steps described in the "Manage Docker as a non-root user" section of https://docs.docker.com/engine/install/linux-postinstall/, but it didn't resolve the problem for me (even after logging out of the session and logging back in)

[peterzahemszky]

Reinstalling Docker using the Docker repository (e.g. following the steps described here) resolved the issue for me

[amk-7]

Hello. When I run docker info I see then:
Client:
Context: default
Debug Mode: false
Plugins:
app: Docker App (Docker Inc., v0.9.1-beta3)
buildx: Docker Buildx (Docker Inc., v0.9.1-docker)
compose: Docker Compose (Docker Inc., v2.12.1)
dev: Docker Dev Environments (Docker Inc., v0.0.3)
extension: Manages Docker extensions (Docker Inc., v0.2.13)
sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc., 0.6.0)
scan: Docker Scan (Docker Inc., v0.21.0)

Server:
ERROR: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
errors pretty printing info

Please can you help me ?