docker.service won't start after apt-get upgrade

[bennettp123]

• This is a bug report
• This is a feature request
• I searched existing issues before opening this one

Expected behavior

docker.service restarts after updating

Actual behavior

docker.service does not start after updating

Steps to reproduce the behavior

bennett@homebridge:~$ apt list --upgradable
containerd.io/focal 1.4.11-1 arm64 [upgradable from: 1.4.10-1]
docker-ce-cli/focal 5:20.10.9~3-0~ubuntu-focal arm64 [upgradable from: 5:20.10.8~3-0~ubuntu-focal]
docker-ce-rootless-extras/focal 5:20.10.9~3-0~ubuntu-focal arm64 [upgradable from: 5:20.10.8~3-0~ubuntu-focal]
docker-ce/focal 5:20.10.9~3-0~ubuntu-focal arm64 [upgradable from: 5:20.10.8~3-0~ubuntu-focal]
libpam-modules-bin/focal-updates 1.3.1-5ubuntu4.3 arm64 [upgradable from: 1.3.1-5ubuntu4.2]
libpam-modules/focal-updates 1.3.1-5ubuntu4.3 arm64 [upgradable from: 1.3.1-5ubuntu4.2]
libpam-runtime/focal-updates 1.3.1-5ubuntu4.3 all [upgradable from: 1.3.1-5ubuntu4.2]
libpam0g/focal-updates 1.3.1-5ubuntu4.3 arm64 [upgradable from: 1.3.1-5ubuntu4.2]

bennett@homebridge:~$ sudo apt-get upgrade

Output of docker version:

bennett@homebridge:~$ sudo docker version
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
Client: Docker Engine - Community
 Cloud integration: 1.0.17
 Version:           20.10.9
 API version:       1.41
 Go version:        go1.16.8
 Git commit:        c2ea9bc
 Built:             Mon Oct  4 16:08:32 2021
 OS/Arch:           linux/arm64
 Context:           default
 Experimental:      true

Output of docker info:

bennett@homebridge:~$ sudo docker info
Client:
 Context:    default
 Debug Mode: false
 Plugins:
  app: Docker App (Docker Inc., v0.9.1-beta3)
  buildx: Build with BuildKit (Docker Inc., v0.6.3-docker)
WARNING: Plugin "/usr/libexec/docker/cli-plugins/docker-compose" is not valid: failed to fetch metadata: fork/exec /usr/libexec/docker/cli-plugins/docker-compose: exec format error

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

Additional environment details (AWS, VirtualBox, physical, etc.)

[bennettp123]

I think I've found the issue

in /var/log/syslog:

Oct  8 08:16:23 homebridge dockerd[2631]: unable to configure the Docker daemon with file /etc/docker/daemon.json: EOF

/etc/docker/daemon.json exists, but is empty

Removing the file fixes the issue

[thaJeztah]

/etc/docker/daemon.json exists, but is empty

Removing the file fixes the issue

Yes, that sounds plausible.

For the next (21.xx) release of docker, I think we're relaxing this validation somewhat, and will ignore an empty file (see moby/moby#42393 (comment)). Might be worth checking where that empty file came from in your situation though.

Let me close this ticket, but feel free to continue the conversation