Check specifically for /lxc/ cgroup

* If cgroup is named lxc, with a container name (hex/alpha/digit/dashes), then its an lxc guest.
* If cgroup is named arbitrarily, then its not necessarily an lxc guest.
* If cgroup capabilities exist, and the cgroup is root (/), then its an lxc host.

2 files changed, 36 insertions, 15 deletions

diff --git a/lib/ohai/plugins/linux/virtualization.rb b/lib/ohai/plugins/linux/virtualization.rb
index 92b8e257..16b0c7bf 100644
--- a/lib/ohai/plugins/linux/virtualization.rb
+++ b/lib/ohai/plugins/linux/virtualization.rb
@@ -128,12 +128,16 @@ Ohai.plugin(:Virtualization) do
     end
 
     # Detect LXC/Docker
-    # Pattern will vary by platform, and init system.
-    # Generally, it will look like this inside a container:
+    #
+    # /proc/self/cgroup will look like this inside a docker container:
     # <index #>:<subsystem>:/lxc/<hexadecimal container id>
     #
-    # Cgroup name, could be arbitrary and named 'Charlie', instead of 'lxc' however.
-    # <index #>:<subsystem>:/<cgroup name>/<hexadecimal container id>
+    # /proc/self/cgroup could have a name including alpha/digit/dashes
+    # <index #>:<subsystem>:/lxc/<named container id>
+    #
+    # /proc/self/cgroup could have a non-lxc cgroup name indicating other uses 
+    # of cgroups.  This is probably not LXC/Docker.
+    # <index #>:<subsystem>:/Charlie
     #
     # A host which supports cgroups, and has capacity to host lxc containers,
     # will show the subsystems and root (/) namespace.
@@ -142,7 +146,7 @@ Ohai.plugin(:Virtualization) do
     # Full notes, https://tickets.opscode.com/browse/OHAI-551
     # Kernel docs, https://www.kernel.org/doc/Documentation/cgroups
     if File.exists?("/proc/self/cgroup")
-      if File.read("/proc/self/cgroup") =~ %r{^\d+:.+:/.+/[\w\d]+$}
+      if File.read("/proc/self/cgroup") =~ %r{^\d+:.+:/lxc/.+$}
         virtualization[:system] = "lxc"
         virtualization[:role] = "guest"
       elsif File.read("/proc/self/cgroup") =~ %r{\d:.+:/$}
diff --git a/spec/unit/plugins/linux/virtualization_spec.rb b/spec/unit/plugins/linux/virtualization_spec.rb
index b2941362..35a8a7bd 100644
--- a/spec/unit/plugins/linux/virtualization_spec.rb
+++ b/spec/unit/plugins/linux/virtualization_spec.rb
@@ -264,7 +264,7 @@ VBOX
   end
 
   describe "when we are checking for lxc" do
-    it "should set lxc guest if /proc/self/cgroup exist and there are /lxc/ mounts" do
+    it "should set lxc guest if /proc/self/cgroup exist and there are /lxc/<hexadecimal> mounts" do
       self_cgroup=<<-CGROUP
 8:blkio:/lxc/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
 7:net_cls:/lxc/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
@@ -282,16 +282,16 @@ CGROUP
       @plugin[:virtualization][:role].should == "guest"
     end
 
-    it "should set lxc guest if /proc/self/cgroup exist and the cgroup is named Charlie" do
+    it "should set lxc guest if /proc/self/cgroup exist and there are /lxc/<name> mounts" do
       self_cgroup=<<-CGROUP
-8:blkio:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-7:net_cls:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-6:freezer:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-5:devices:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-4:memory:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-3:cpuacct:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-2:cpu:/Charlie/baa660ed81bc81d262ac6e19486142aeec5fce2043e2a173eb2505c6fbed89bc
-1:cpuset:/
+8:blkio:/lxc/vanilla
+7:net_cls:/lxc/vanilla
+6:freezer:/lxc/vanilla
+5:devices:/lxc/vanilla
+4:memory:/lxc/vanilla
+3:cpuacct:/lxc/vanilla
+2:cpu:/lxc/vanilla
+1:cpuset:/lxc/vanilla
 CGROUP
       File.should_receive(:exists?).with("/proc/self/cgroup").and_return(true)
       File.stub(:read).with("/proc/self/cgroup").and_return(self_cgroup)
@@ -300,6 +300,23 @@ CGROUP
       @plugin[:virtualization][:role].should == "guest"
     end
 
+    it "should set not set anyting if /proc/self/cgroup exist and the cgroup is named arbitrarily, it isn't necessarily lxc." do
+      self_cgroup=<<-CGROUP
+8:blkio:/Charlie
+7:net_cls:/Charlie
+6:freezer:/Charlie
+5:devices:/Charlie
+4:memory:/Charlie
+3:cpuacct:/Charlie
+2:cpu:/Charlie
+1:cpuset:/Charlie
+CGROUP
+      File.should_receive(:exists?).with("/proc/self/cgroup").and_return(true)
+      File.stub(:read).with("/proc/self/cgroup").and_return(self_cgroup)
+      @plugin.run
+      @plugin[:virtualization].should == {}
+    end
+
     it "should set lxc host if /proc/self/cgroup only has / mounts" do
       self_cgroup=<<-CGROUP
 8:blkio:/