Why the services do not start at installation?

Question

I've seen this sometime now, but not finding anything in the ubuntu man about this peculiar policy-rc.d binary that prevents services from being started/restarted/stopped when called by dpkg/apt, so I would like to know what is the reason of this.

Setting up lxc (0.9.0-0ubuntu3.6) ...
invoke-rc.d: policy-rc.d denied execution of start.
invoke-rc.d: policy-rc.d denied execution of start.
invoke-rc.d: policy-rc.d denied execution of start.

Apparently, no package owns this binary:

dpkg -S /usr/sbin/policy-rc.d
dpkg-query: no path found matching pattern /usr/sbin/policy-rc.d

Solution

This "script" is included in the sysv-rc package. This is part of a Debian policy which allows sysadmins to control what services starts/restarts/stops whenever they install/upgrade/uninstall packages:

POLICY-RC.D Policy layer (/usr/sbin/policy-rc.d) interface:

Most Debian systems will not have this script as the need for a policy layer is not very common. Most people using chroot jails just need an one-line script which returns an exit status of 101 as the jailed /usr/sbin/policy-rc.d script.

The /usr/sbin/policy-rc.d file must be managed through the alternatives system (/usr/sbin/update-alternatives) by any packages providing it.

/usr/sbin/policy-rc.d [options] []

/usr/sbin/policy-rc.d [options] --list [...]

(Source)

So, what happens here? Well, whenever this script is present it will return a code which states the current policy of the local system (which is by default 101 = action forbidden by policy). If you want to change the policy, just modify the file as root to any of this values:

  0 - action allowed
  1 - unknown action (therefore, undefined policy)
 100 - unknown initscript id
 101 - action forbidden by policy
 102 - subsystem error
 103 - syntax error
 104 - [reserved]
 105 - behaviour uncertain, policy undefined.
 106 - action not allowed. Use the returned fallback actions
       (which are implied to be "allowed") instead. 

The script is still a place holder, but when completed all these values could be returned. If you want to allow any change just change exit 101 for exit 0 and done. Whenever you install/remove/upgrade a service these will be (re)started/stopped.

Comments

[Tjorriemorrie]

Docker images has a fixed exit 101 # For most Docker users, "apt-get install" only happens during "docker build", # where starting services doesn't work and often fails in humorous ways. This # prevents those failures by stopping the services from attempting to start.

[Jonny Flowers]

@Tjorriemorrie please can you elaborate? I am having this issue when building a docker image and I seem to be unable to fix it

[David Portabella]

possible solution: monblocnotes.com/node/2057

[Bigood]

@JonnyFlowers He refers to these lines, in docker's source

[Calyfs0]

@Bigood: the line number changed in the recent master branch. Here is [a permalink to the lines in docker's source(github.com/moby/moby/blob/v17.05.0-ce/contrib/mkimage‌​/…).