Package docker.io cannot be purged

[Johnny Ooi]

After installing docker.io in Artful, then attempting to purge it, it asks for confirmation, then complains it cannot nuke /var/lib/docker. An almost identical error to this Debian bug

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=856149

/var/lib/docker/nuke-graph-directory.sh: 64: /var/lib/docker/nuke-graph-directory.sh: shopt: not found

Running rm -rf /var/lib/docker then trying to purge docker.io again worked and then gave me a warning about /etc/docker not being empty. So rm -rf /etc/docker and purge again then worked.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: docker.io (not installed)
ProcVersionSignature: Ubuntu 4.13.0-39.44-generic 4.13.16
Uname: Linux 4.13.0-39-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.8
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Tue May 1 10:16:19 2018
InstallationDate: Installed on 2018-04-15 (15 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105.1)
SourcePackage: docker.io
UpgradeStatus: No upgrade log present (probably fresh install)