[Bug 1577001] [NEW] Installing lxd leaves /var/lib/lxd/unix.socket with wrong group ownership

[Martin Pitt]

I can reproduce this bug in a small (autopkgtest) Xenial VM with

  dpkg -P lxd; rm /var/lib/lxd/unix.socket; apt-get install -y lxd; ls
-l /var/lib/lxd/unix.socket

But I cannot reproduce this as long as the lxd package is already
installed, all these work fine:

  systemctl stop lxd.{service,socket} lxd-containers; rm
/var/lib/lxd/unix.socket; systemctl reset-failed lxd.{service,socket}
lxd-containers; DEBIAN_FRONTEND=noninteractive dpkg-reconfigure lxd; ls
-l /var/lib/lxd/unix.socket

  systemctl stop lxd.{service,socket} lxd-containers; rm
/var/lib/lxd/unix.socket; systemctl reset-failed lxd.{service,socket}
lxd-containers; DEBIAN_FRONTEND=noninteractive apt-get install
--reinstall lxd; ls -l /var/lib/lxd/unix.socket

  systemctl stop lxd.{service,socket} lxd-containers; rm
/var/lib/lxd/unix.socket; systemctl reset-failed lxd.{service,socket}
lxd-containers; export DPKG_MAINTSCRIPT_PACKAGE=lxd; deb-systemd-helper
enable lxd.service; deb-systemd-helper enable lxd.socket; deb-systemd-
helper enable lxd-containers.service; deb-systemd-invoke start lxd-
containers.service; deb-systemd-invoke start lxd.socket; ls -l
/var/lib/lxd/unix.socket

(The reset-failed is to avoid the "unit restarted too often" rate limit
when running these too often)

More interestingly, I also cannot reproduce the bug with the first
command if I stop the socket unit before or after purging:

  systemctl stop lxd.socket; dpkg -P lxd; rm /var/lib/lxd/unix.socket;
apt-get install -y lxd; ls -l /var/lib/lxd/unix.socket

  dpkg -P lxd; systemctl stop lxd.socket; rm /var/lib/lxd/unix.socket;
apt-get install -y lxd; ls -l /var/lib/lxd/unix.socket

This exhibits a bug in lxd's maintainer scripts: Purging lxd still
leaves lxd.socket running. Re-adding an lxd task about this, it needs
the counterpart of starting lxd.socket in the postinst.

> Adding logging to the package's postinst shows that, if /var/lib/lxd/unix.socket did not already exist, it is created by the line
> deb-systemd-helper enable lxd.service

Most of "deb-systemd-helper enable" shouldn't affect the permissions of
unix.socket at all, as this is just creating symlinks in
/etc/systemd/system/ (without even calling systemctl for that). So I
figure the "systemctl daemon-reload" at the very end triggers this. And
indeed:

  mv /lib/systemd/system/lxd.socket{,.disabled}; systemctl daemon-reload; sleep 0.5; mv /lib/systemd/system/lxd.socket{.disabled,}; systemctl daemon-reload; sleep 0.5; ls -l /var/lib/lxd/unix.socket
  srw-rw---- 1 root root 0 May  1 18:22 /var/lib/lxd/unix.socket

This is inconsistent -- either unix.socket should not be created at all
(as the unit is still running) or with correct permissions.

@Dan: Is this reproducible for you on a 16.04 install that has lxd
purged, no /var/lib/lxd/unix.socket, and lxd.socket *not* running? (Note
that 16.04 comes with lxd preinstalled on server and cloud images) I. e.
do you only see this on reinstall or on a clean install of lxd? If so,
we have another bug, but if "systemctl status lxd.socket" is running
before the reinstall it's the issue I described above.

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https://bugs.launchpad.net/bugs/1577001

Title:
  Installing lxd leaves /var/lib/lxd/unix.socket with wrong group
  ownership

Status in lxd package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  On ubuntu 16.04, doing
    sudo apt-get install lxd
  sometimes leaves the file
    /var/lib/lxd/unix.socket
  with group root, but it should have group lxd.   Doing
    sudo systemctl restart lxd.socket
  rescues the file and gives it the right group ownership.

  Adding logging to the package's postinst shows that, if /var/lib/lxd/unix.socket did not already exist, it is created by the line
   deb-systemd-helper enable lxd.service
  and with the wrong group permissions.
  If the socket already existed with the correct group ownership that command breaks the permissions and sets it to be group root.

  It's about 90% repeatable on one machine here (with an SSD main disk).

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: lxd 2.0.0-0ubuntu4
  ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
  Uname: Linux 4.4.0-21-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Sat Apr 30 08:24:53 2016
  InstallationDate: Installed on 2016-03-26 (35 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Beta amd64 (20160323)
  SourcePackage: lxd
  UpgradeStatus: No upgrade log present (probably fresh install)

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