Add support for unprivileged containers

fixes #312

I've also remove the "EXPERIMENTAL" flag to bridge support in the README.
It's been there long enough.

README.md

@@ -78,7 +78,7 @@ prior to starting it.
 
 For other configuration options, please check the [lxc.conf manpages](http://manpages.ubuntu.com/manpages/precise/man5/lxc.conf.5.html).
 
-### Private Networks [EXPERIMENTAL]
+### Private Networks
 
 Starting with vagrant-lxc 1.1.0, there is some rudimentary support for configuring
 [Private Networks](https://docs.vagrantup.com/v2/networking/private_network.html)
@@ -137,25 +137,29 @@ Vagrant.configure("2") do |config|
 end
 ```
 
-For old versions of lxc (like 0.7.5 shipped with Ubuntu 12.04 by default) that
-does not support `best` for the backingstore option, changing it to `none` is
-required and a default for all Vagrant environments can be set from your
-`~/.vagrant.d/Vagrantfile` using the same `provider` block:
+## Unprivileged containers support
+
+Since v1.4.0, `vagrant-lxc` gained support for unprivileged containers. For now, since it's a new
+feature, privileged containers are still the default, but you can have your `Vagrantfile` use
+unprivileged containers with the `privileged` flag (which defaults to `true`). Example:
 
 ```ruby
 Vagrant.configure("2") do |config|
   config.vm.provider :lxc do |lxc|
-    lxc.backingstore = 'none'
+    lxc.privileged = false
   end
 end
 ```
 
+For unprivileged containers to work with `vagrant-lxc`, you need a properly configured system. On
+some distros, it can be somewhat of a challenge. Your journey to configuring your system can start
+with [Stéphane Graber's blog post about it](https://stgraber.org/2014/01/17/lxc-1-0-unprivileged-containers/).
+
 ## Avoiding `sudo` passwords
 
-This plugin requires **a lot** of `sudo`ing since [unprivileged containers](https://github.com/fgrehm/vagrant-lxc/issues/312)
-are not supported yet. To work around that, you can use the `vagrant lxc sudoers`
-command which will create a file under `/etc/sudoers.d/vagrant-lxc` whitelisting
-all commands required by `vagrant-lxc` to run.
+If you're not using unprivileged containers, this plugin requires **a lot** of `sudo`ing To work
+around that, you can use the `vagrant lxc sudoers` command which will create a file under
+`/etc/sudoers.d/vagrant-lxc` whitelisting all commands required by `vagrant-lxc` to run.
 
 If you are interested on what will be generated by that command, please check
 [this code](lib/vagrant-lxc/command/sudoers.rb).

lib/vagrant-lxc/action/create.rb

@@ -19,10 +19,14 @@ module Vagrant
               container_name = generate_container_name(env)
           end
 
+          backingstore = config.backingstore
+          if backingstore.nil?
+            backingstore = config.privileged ? "best" : "dir"
+          end
           driver = env[:machine].provider.driver
           driver.create(
             container_name,
-            config.backingstore,
+            backingstore,
             config.backingstore_options,
             env[:lxc_template_src],
             env[:lxc_template_config],

lib/vagrant-lxc/config.rb

@@ -24,6 +24,12 @@ module Vagrant
 
       attr_accessor :fetch_ip_tries
 
+      # Whether the container needs to be privileged. Defaults to true (unprivileged containers
+      # is a very new feature in vagrant-lxc). If false, will try creating an unprivileged
+      # container. If it can't, will revert to the old "sudo wrapper" method to create a privileged
+      # container.
+      attr_accessor :privileged
+
       def initialize
         @customizations = []
         @backingstore = UNSET_VALUE
@@ -31,6 +37,7 @@ module Vagrant
         @container_name = UNSET_VALUE
         @tmpfs_mount_size = UNSET_VALUE
         @fetch_ip_tries = UNSET_VALUE
+        @privileged = UNSET_VALUE
       end
 
       # Customize the container by calling `lxc-start` with the given
@@ -55,10 +62,11 @@ module Vagrant
 
       def finalize!
         @container_name = nil if @container_name == UNSET_VALUE
-        @backingstore = "best" if @backingstore == UNSET_VALUE
+        @backingstore = nil if @backingstore == UNSET_VALUE
         @existing_container_name = nil if @existing_container_name == UNSET_VALUE
         @tmpfs_mount_size = '2G' if @tmpfs_mount_size == UNSET_VALUE
         @fetch_ip_tries = 10 if @fetch_ip_tries == UNSET_VALUE
+        @privileged = true if @privileged == UNSET_VALUE
       end
     end
   end

lib/vagrant-lxc/driver.rb

@@ -20,9 +20,9 @@ module Vagrant
       attr_reader :container_name,
                   :customizations
 
-      def initialize(container_name, sudo_wrapper = nil, cli = nil)
+      def initialize(container_name, sudo_wrapper = nil, cli = nil, privileged: true)
         @container_name = container_name
-        @sudo_wrapper   = sudo_wrapper || SudoWrapper.new()
+        @sudo_wrapper   = sudo_wrapper || SudoWrapper.new(privileged: privileged)
         @cli            = cli || CLI.new(@sudo_wrapper, container_name)
         @logger         = Log4r::Logger.new("vagrant::provider::lxc::driver")
         @customizations = []
@@ -266,12 +266,21 @@ module Vagrant
       end
 
       def write_config(contents)
-        Tempfile.new('lxc-config').tap do |file|
-          file.chmod 0644
-          file.write contents
-          file.close
-          @sudo_wrapper.run 'cp', '-f', file.path, config_path
-          @sudo_wrapper.run 'chown', 'root:root', config_path
+        confpath = base_path.join('config').to_s
+        begin
+          File.open(confpath, File::RDWR) do |file|
+            file.write contents
+          end
+        rescue
+          # We don't have permissions to write in the conf file. That's probably because it's a
+          # privileged container. Work around that through sudo_wrapper.
+          Tempfile.new('lxc-config').tap do |file|
+            file.chmod 0644
+            file.write contents
+            file.close
+            @sudo_wrapper.run 'cp', '-f', file.path, confpath
+            @sudo_wrapper.run 'chown', 'root:root', confpath
+          end
         end
       end
     end

lib/vagrant-lxc/provider.rb

@@ -2,7 +2,6 @@ require "log4r"
 
 require "vagrant-lxc/action"
 require "vagrant-lxc/driver"
-require "vagrant-lxc/sudo_wrapper"
 
 module Vagrant
   module LXC
@@ -27,7 +26,7 @@ module Vagrant
 
       def ensure_lxc_installed!
         begin
-          SudoWrapper.new().run("which", "lxc-create")
+          SudoWrapper.new(privileged: @machine.provider_config.privileged).run("which", "lxc-create")
         rescue Vagrant::LXC::Errors::ExecuteError
           raise Errors::LxcNotInstalled
         end
@@ -40,7 +39,7 @@ module Vagrant
 
         begin
           @logger.debug("Instantiating the container for: #{id.inspect}")
-          @driver = Driver.new(id)
+          @driver = Driver.new(id, privileged: @machine.provider_config.privileged)
           @driver.validate!
         rescue Driver::ContainerNotFound
           # The container doesn't exist, so we probably have a stale

lib/vagrant-lxc/sudo_wrapper.rb

@@ -10,8 +10,9 @@ module Vagrant
         "/usr/local/bin/vagrant-lxc-wrapper"
       end
 
-      def initialize()
+      def initialize(privileged: true)
         @wrapper_path = Pathname.new(SudoWrapper.dest_path).exist? && SudoWrapper.dest_path || nil
+        @privileged   = privileged
         @logger       = Log4r::Logger.new("vagrant::lxc::sudo_wrapper")
       end
 
@@ -27,11 +28,15 @@ module Vagrant
         File.umask(old_mask & 022)  # allow all `r` and `x` bits
 
         begin
-          if @wrapper_path && !options[:no_wrapper]
-            command.unshift @wrapper_path
-            execute *(['sudo'] + command)
+          if @privileged
+            if @wrapper_path && !options[:no_wrapper]
+              command.unshift @wrapper_path
+              execute *(['sudo'] + command)
+            else
+              execute *(['sudo', '/usr/bin/env'] + command)
+            end
           else
-            execute *(['sudo', '/usr/bin/env'] + command)
+            execute *(['/usr/bin/env'] + command)
           end
         ensure
           File.umask(old_mask)