Verifying the Install

Verifying the Installation with docker version and docker info

docker version reports the client and every server component:

Client and server versionsShell

docker version

Output

Client: Docker Engine - Community
 Version:           29.8.1
 ...
Server: Docker Engine - Community
 Engine:
  Version:          29.8.1
  API version:      1.56 (minimum version 1.40)
  ...
 containerd:
  Version:          v2.3.5
  ...

A missing Server: half with "permission denied" means your shell is not in the docker group yet; "Cannot connect to the Docker 514 daemon" means the service is down. docker info shows how the daemon is configured:

The daemon's configuration at a glanceShell

docker info

Output

...
 Storage Driver: overlayfs
  driver-type: io.containerd.snapshotter.v1
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 ...
 Operating System: Ubuntu 26.04.1 LTS
 ...
 Live Restore Enabled: false

Check the storage driver (containerd 234,762 's snapshotter), the cgroup driver and version, and the logging driver: json-file never rotates by default, which daemon.json fixes. Problems appear as WARNING: lines at the end. Finally, hello-world exercises the whole chain:

The traditional first containerShell

docker run --rm hello-world

Output

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
...
Status: Downloaded newer image for hello-world:latest
Hello from Docker!
This message shows that your installation appears to be working correctly.
...

The full message lists the chain from containerd and runc: client, daemon, pull, create, stream. --rm deletes the container; the image stays cached.

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