Already created docker group prevents package docker.io 1.13.1-0ubuntu1~16.04.2 install

[korziner]

Did add docker group before running installer.
This caused postinst script exit on the step of creating docker group.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: docker.io 1.13.1-0ubuntu1~16.04.2
ProcVersionSignature: Ubuntu 4.13.0-36.40~16.04.1-generic 4.13.13
Uname: Linux 4.13.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
Date: Fri Mar 9 03:57:35 2018
ErrorMessage: подпроцесс установлен сценарий post-installation возвратил код ошибки 1
InstallationDate: Installed on 2018-03-04 (4 days ago)
InstallationMedia: Xubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.3
 apt 1.2.25
SourcePackage: docker.io
Title: package docker.io 1.13.1-0ubuntu1~16.04.2 failed to install/upgrade: подпроцесс установлен сценарий post-installation возвратил код ошибки 1
UpgradeStatus: No upgrade log present (probably fresh install)

[Tianon Gravi (tianon)]

I'm guessing you added the group as a non-system group?
(resulting in "addgroup: The group `docker' already exists and is not a system group. Exiting.")

I think it would probably be sane to add a check similar to the one Docker itself uses (namely whether "/etc/group" includes a line that starts with "docker:" -- ie, not using "getent group" since Docker parses the file directly).

something like:

| if ! grep -q '^docker:' /etc/group 2>/dev/null; then
| addgroup --system docker
| fi

---

See also:

https://github.com/moby/moby/blob/3a633a712c8bbb863fe7e57ec132dd87a9c4eff7/daemon/listeners/group_unix.go#L20

https://github.com/opencontainers/runc/blob/69663f0bd4b60df09991c08812a60108003fa340/libcontainer/user/lookup_unix.go#L15