Merge branch 'joeyconfig'

11 files changed, 356 insertions, 76 deletions

diff --git a/src/Propellor.hs b/src/Propellor.hs
index c0ef14f4..6e31e27c 100644
--- a/src/Propellor.hs
+++ b/src/Propellor.hs
@@ -33,6 +33,7 @@ module Propellor (
 	  module Propellor.Types
 	, module Propellor.Property
 	, module Propellor.Property.Cmd
+	, module Propellor.Host
 	, module Propellor.Info
 	, module Propellor.PrivData
 	, module Propellor.Engine
@@ -51,6 +52,7 @@ import Propellor.PrivData
 import Propellor.Message
 import Propellor.Exception
 import Propellor.Info
+import Propellor.Host
 
 import Utility.PartialPrelude as X
 import Utility.Process as X
diff --git a/src/Propellor/CmdLine.hs b/src/Propellor/CmdLine.hs
index 061c9700..466b60f5 100644
--- a/src/Propellor/CmdLine.hs
+++ b/src/Propellor/CmdLine.hs
@@ -15,7 +15,8 @@ import Propellor.Git
 import Propellor.Ssh
 import Propellor.Server
 import qualified Propellor.Property.Docker as Docker
-import qualified Propellor.Property.Docker.Shim as DockerShim
+import qualified Propellor.Property.Chroot as Chroot
+import qualified Propellor.Shim as Shim
 import Utility.SafeCommand
 
 usage :: Handle -> IO ()
@@ -72,7 +73,7 @@ processCmdLine = go =<< getArgs
 -- | Runs propellor on hosts, as controlled by command-line options.
 defaultMain :: [Host] -> IO ()
 defaultMain hostlist = do
-	DockerShim.cleanEnv
+	Shim.cleanEnv
 	checkDebugMode
 	cmdline <- processCmdLine
 	debug ["command line: ", show cmdline]
@@ -85,6 +86,7 @@ defaultMain hostlist = do
 	go _ ListFields = listPrivDataFields hostlist
 	go _ (AddKey keyid) = addKey keyid
 	go _ (DockerChain hn cid) = Docker.chain hostlist hn cid
+	go _ (ChrootChain hn loc) = Chroot.chain hostlist hn loc
 	go _ (DockerInit hn) = Docker.init hn
 	go _ (GitPush fin fout) = gitPushHelper fin fout
 	go _ (Update _) = forceConsole >> fetchFirst (onlyprocess update)
diff --git a/src/Propellor/Engine.hs b/src/Propellor/Engine.hs
index 3fa9ffc0..969769ce 100644
--- a/src/Propellor/Engine.hs
+++ b/src/Propellor/Engine.hs
@@ -11,12 +11,15 @@ import "mtl" Control.Monad.Reader
 import Control.Exception (bracket)
 import System.PosixCompat
 import System.Posix.IO
+import Data.Maybe
 
 import Propellor.Types
 import Propellor.Message
 import Propellor.Exception
 import Propellor.Info
 import Utility.Exception
+import Utility.PartialPrelude
+import Utility.Monad
 
 runPropellor :: Host -> Propellor a -> IO a
 runPropellor host a = runReaderT (runWithHost a) host
@@ -62,3 +65,18 @@ onlyProcess lockfile a = bracket lock unlock (const a)
 		return l
 	unlock = closeFd
 	alreadyrunning = error "Propellor is already running on this host!"
+
+-- | Reads and displays each line from the Handle, except for the last line
+-- which is a Result.
+processChainOutput :: Handle -> IO Result
+processChainOutput h = go Nothing
+  where
+	go lastline = do
+		v <- catchMaybeIO (hGetLine h)
+		case v of
+			Nothing -> pure $ fromMaybe FailedChange $
+				readish =<< lastline
+			Just s -> do
+				maybe noop (\l -> unless (null l) (putStrLn l)) lastline
+				hFlush stdout
+				go (Just s)
diff --git a/src/Propellor/Host.hs b/src/Propellor/Host.hs
new file mode 100644
index 00000000..14d56e20
--- /dev/null
+++ b/src/Propellor/Host.hs
@@ -0,0 +1,64 @@
+{-# LANGUAGE PackageImports #-}
+
+module Propellor.Host where
+
+import Data.Monoid
+import qualified Data.Set as S
+
+import Propellor.Types
+import Propellor.Info
+import Propellor.Property
+import Propellor.PrivData
+
+-- | Starts accumulating the properties of a Host.
+--
+-- > host "example.com"
+-- > 	& someproperty
+-- > 	! oldproperty
+-- > 	& otherproperty
+host :: HostName -> Host
+host hn = Host hn [] mempty
+
+-- | Something that can accumulate properties.
+class Hostlike h where
+	-- | Adds a property.
+	--
+	-- Can add Properties and RevertableProperties
+	(&) :: IsProp p => h -> p -> h
+
+	-- | Like (&), but adds the property as the
+	-- first property of the host. Normally, property
+	-- order should not matter, but this is useful
+	-- when it does.
+	(&^) :: IsProp p => h -> p -> h
+
+	getHost :: h -> Host
+
+instance Hostlike Host where
+	(Host hn ps is) &  p = Host hn (ps ++ [toProp p]) (is <> getInfo p)
+	(Host hn ps is) &^ p = Host hn ([toProp p] ++ ps) (getInfo p <> is)
+	getHost h = h
+
+-- | Adds a property in reverted form.
+(!) :: Hostlike h => h -> RevertableProperty -> h
+h ! p = h & revert p
+
+infixl 1 &^
+infixl 1 &
+infixl 1 !
+
+-- | When eg, docking a container, some of the Info about the container
+-- should propigate out to the Host it's on. This includes DNS info,
+-- so that eg, aliases of the container are reflected in the dns for the
+-- host where it runs.
+--
+-- This adjusts the Property that docks a container, to include such info
+-- from the container.
+propigateInfo :: Hostlike hl => hl -> Property -> (Info -> Info) -> Property
+propigateInfo hl p f = combineProperties (propertyDesc p) $
+	p' : dnsprops ++ privprops
+  where
+	p' = p { propertyInfo = f (propertyInfo p) }
+	i = hostInfo (getHost hl)
+	dnsprops = map addDNS (S.toList $ _dns i)
+	privprops = map addPrivDataField (S.toList $ _privDataFields i)
diff --git a/src/Propellor/Property.hs b/src/Propellor/Property.hs
index bf69ff60..6ace5e4e 100644
--- a/src/Propellor/Property.hs
+++ b/src/Propellor/Property.hs
@@ -3,6 +3,7 @@
 module Propellor.Property where
 
 import System.Directory
+import System.FilePath
 import Control.Monad
 import Data.Monoid
 import Control.Monad.IfElse
@@ -12,7 +13,6 @@ import Propellor.Types
 import Propellor.Info
 import Propellor.Engine
 import Utility.Monad
-import System.FilePath
 
 -- Constructs a Property.
 property :: Desc -> Propellor Result -> Property
@@ -131,42 +131,6 @@ boolProperty desc a = property desc $ ifM (liftIO a)
 revert :: RevertableProperty -> RevertableProperty
 revert (RevertableProperty p1 p2) = RevertableProperty p2 p1
 
--- | Turns a revertable property into a regular property.
-unrevertable :: RevertableProperty -> Property
-unrevertable (RevertableProperty p1 _p2) = p1
-
--- | Starts accumulating the properties of a Host.
---
--- > host "example.com"
--- > 	& someproperty
--- > 	! oldproperty
--- > 	& otherproperty
-host :: HostName -> Host
-host hn = Host hn [] mempty
-
-class Hostlike h where
-	-- | Adds a property to a Host
-	--
-	-- Can add Properties and RevertableProperties
-	(&) :: IsProp p => h -> p -> h
-	-- | Like (&), but adds the property as the
-	-- first property of the host. Normally, property
-	-- order should not matter, but this is useful
-	-- when it does.
-	(&^) :: IsProp p => h -> p -> h
-
-instance Hostlike Host where
-	(Host hn ps is) &  p = Host hn (ps ++ [toProp p]) (is <> getInfo p)
-	(Host hn ps is) &^ p = Host hn ([toProp p] ++ ps) (getInfo p <> is)
-
--- | Adds a property to the Host in reverted form.
-(!) :: Hostlike h => h -> RevertableProperty -> h
-h ! p = h & revert p
-
-infixl 1 &^
-infixl 1 &
-infixl 1 !
-
 -- Changes the action that is performed to satisfy a property. 
 adjustProperty :: Property -> (Propellor Result -> Propellor Result) -> Property
 adjustProperty p f = p { propertySatisfy = f (propertySatisfy p) }
diff --git a/src/Propellor/Property/Chroot.hs b/src/Propellor/Property/Chroot.hs
new file mode 100644
index 00000000..798330b0
--- /dev/null
+++ b/src/Propellor/Property/Chroot.hs
@@ -0,0 +1,130 @@
+module Propellor.Property.Chroot (
+	Chroot(..),
+	chroot,
+	provisioned,
+	chain,
+) where
+
+import Propellor
+import qualified Propellor.Property.Debootstrap as Debootstrap
+import qualified Propellor.Shim as Shim
+import Utility.SafeCommand
+
+import qualified Data.Map as M
+import Data.List.Utils
+import System.Posix.Directory
+
+data Chroot = Chroot FilePath System Host
+
+instance Hostlike Chroot where
+	(Chroot l s h) & p = Chroot l s (h & p)
+	(Chroot l s h) &^ p = Chroot l s (h &^ p)
+	getHost (Chroot _ _ h) = h
+
+-- | Defines a Chroot at the given location, containing the specified
+-- System. Properties can be added to configure the Chroot.
+--
+-- > chroot "/srv/chroot/ghc-dev" (System (Debian Unstable) "amd64")
+-- >    & Apt.installed ["build-essential", "ghc", "haskell-platform"]
+-- >	& ...
+chroot :: FilePath -> System -> Chroot
+chroot location system = Chroot location system (Host location [] mempty)
+
+-- | Ensures that the chroot exists and is provisioned according to its
+-- properties.
+--
+-- Reverting this property removes the chroot. Note that it does not ensure
+-- that any processes that might be running inside the chroot are stopped.
+provisioned :: Chroot -> RevertableProperty
+provisioned c@(Chroot loc system _) = RevertableProperty
+	(propigateChrootInfo c (go "exists" setup))
+	(go "removed" teardown)
+  where
+	go desc a = property (chrootDesc c desc) $ ensureProperties [a]
+
+	setup = provisionChroot c `requires` built
+	
+	built = case system of
+		(System (Debian _) _) -> debootstrap
+		(System (Ubuntu _) _) -> debootstrap
+
+	debootstrap = toProp (Debootstrap.built loc system [])
+
+	teardown = undefined
+
+propigateChrootInfo :: Chroot -> Property -> Property
+propigateChrootInfo c p = propigateInfo c p (<> chrootInfo c)
+
+chrootInfo :: Chroot -> Info
+chrootInfo (Chroot loc _ h) =
+	mempty { _chrootinfo = mempty { _chroots = M.singleton loc h } }
+
+-- | Propellor is run inside the chroot to provision it.
+--
+-- Strange and wonderful tricks let the host's /usr/local/propellor
+-- be used inside the chroot, without needing to install anything.
+provisionChroot :: Chroot -> Property
+provisionChroot c@(Chroot loc _ _) = property (chrootDesc c "provisioned") $ do
+	let d = localdir </> shimdir c
+	let me = localdir </> "propellor"
+	shim <- liftIO $ ifM (doesDirectoryExist d)
+		( pure (Shim.file me d)
+		, Shim.setup me d
+		)
+	ifM (liftIO $ bindmount shim)
+		( chainprovision shim
+		, return FailedChange
+		)
+  where
+	bindmount shim = ifM (doesFileExist (loc ++ shim))
+		( return True
+		, do
+			let mntpnt = loc ++ localdir
+			createDirectoryIfMissing True mntpnt
+			boolSystem "mount"
+				[ Param "--bind"
+				, File localdir, File mntpnt
+				]
+		)
+	
+	chainprovision shim = do
+		parenthost <- asks hostName
+		let p = inChrootProcess c
+			[ shim
+			, "--continue"
+			, show $ toChain parenthost c
+			]
+		liftIO $ withHandle StdoutHandle createProcessSuccess p
+			processChainOutput
+
+toChain :: HostName -> Chroot -> CmdLine
+toChain parenthost (Chroot loc _ _) = ChrootChain parenthost loc
+
+chain :: [Host] -> HostName -> FilePath -> IO ()
+chain hostlist hn loc = case findHostNoAlias hostlist hn of
+	Nothing -> errorMessage ("cannot find host " ++ hn)
+	Just parenthost -> case M.lookup loc (_chroots $ _chrootinfo $ hostInfo parenthost) of
+		Nothing -> errorMessage ("cannot find chroot " ++ loc ++ " on host " ++ hn)
+		Just h -> go h
+  where
+	go h = do
+		changeWorkingDirectory localdir
+		forceConsole
+		onlyProcess (provisioningLock loc) $ do
+			r <- runPropellor h $ ensureProperties $ hostProperties h
+			putStrLn $ "\n" ++ show r
+
+inChrootProcess :: Chroot -> [String] -> CreateProcess
+inChrootProcess (Chroot loc _ _) cmd = proc "chroot" (loc:cmd)
+
+provisioningLock :: FilePath -> FilePath
+provisioningLock containerloc = "chroot" </> mungeloc containerloc ++ ".lock"
+
+shimdir :: Chroot -> FilePath
+shimdir (Chroot loc _ _) = "chroot" </> mungeloc loc ++ ".shim"
+
+mungeloc :: FilePath -> String
+mungeloc = replace "/" "_"
+
+chrootDesc :: Chroot -> String -> String
+chrootDesc (Chroot loc _ _) desc = "chroot " ++ loc ++ " " ++ desc
diff --git a/src/Propellor/Property/Debootstrap.hs b/src/Propellor/Property/Debootstrap.hs
index 4e7bc740..5f521c32 100644
--- a/src/Propellor/Property/Debootstrap.hs
+++ b/src/Propellor/Property/Debootstrap.hs
@@ -33,7 +33,7 @@ built target system@(System _ arch) extraparams =
 	RevertableProperty setup teardown
   where
 	setup = check (unpopulated target <||> ispartial) setupprop
-		`requires` unrevertable installed
+		`requires` toProp installed
 	
 	teardown = check (not <$> unpopulated target) teardownprop
 	
diff --git a/src/Propellor/Property/Docker.hs b/src/Propellor/Property/Docker.hs
index 676d323a..5cf60ff9 100644
--- a/src/Propellor/Property/Docker.hs
+++ b/src/Propellor/Property/Docker.hs
@@ -41,7 +41,7 @@ module Propellor.Property.Docker (
 import Propellor hiding (init)
 import qualified Propellor.Property.File as File
 import qualified Propellor.Property.Apt as Apt
-import qualified Propellor.Property.Docker.Shim as Shim
+import qualified Propellor.Shim as Shim
 import Utility.SafeCommand
 import Utility.Path
 import Utility.ThreadScheduler
@@ -52,7 +52,6 @@ import System.Posix.Process
 import Prelude hiding (init)
 import Data.List hiding (init)
 import Data.List.Utils
-import qualified Data.Set as S
 import qualified Data.Map as M
 
 installed :: Property
@@ -78,8 +77,10 @@ data Container = Container Image Host
 instance Hostlike Container where
 	(Container i h) & p = Container i (h & p)
 	(Container i h) &^ p = Container i (h &^ p)
+	getHost (Container _ h) = h
 
--- | Builds a Container with a given name, image, and properties.
+-- | Defines a Container with a given name, image, and properties.
+-- Properties can be added to configure the Container.
 --
 -- > container "web-server" "debian"
 -- >    & publish "80:80"
@@ -100,11 +101,9 @@ container cn image = Container image (Host cn [] info)
 --
 -- Reverting this property ensures that the container is stopped and
 -- removed.
-docked
-	:: Container
-	-> RevertableProperty
+docked :: Container -> RevertableProperty
 docked ctr@(Container _ h) = RevertableProperty
-	(propigateInfo ctr (go "docked" setup))
+	(propigateContainerInfo ctr (go "docked" setup))
 	(go "undocked" teardown)
   where
 	cn = hostName h
@@ -131,14 +130,12 @@ docked ctr@(Container _ h) = RevertableProperty
 					]
 			]
 
-propigateInfo :: Container -> Property -> Property
-propigateInfo (Container _ h@(Host hn _ containerinfo)) p =
-	combineProperties (propertyDesc p) $ p' : dnsprops ++ privprops
+propigateContainerInfo :: Container -> Property -> Property
+propigateContainerInfo ctr@(Container _ h) p =
+	propigateInfo ctr p (<> dockerinfo)
   where
-	p' = p { propertyInfo = propertyInfo p <> dockerinfo }
-	dockerinfo = dockerInfo $ mempty { _dockerContainers = M.singleton hn h }
-	dnsprops = map addDNS (S.toList $ _dns containerinfo)
-	privprops = map addPrivDataField (S.toList $ _privDataFields containerinfo)
+	dockerinfo = dockerInfo $
+		mempty { _dockerContainers = M.singleton (hostName h) h }
 
 mkContainerInfo :: ContainerId -> Container -> ContainerInfo
 mkContainerInfo cid@(ContainerId hn _cn) (Container img h) = 
@@ -435,20 +432,10 @@ provisionContainer cid = containerDesc cid $ property "provisioned" $ liftIO $ d
 		[ if isConsole msgh then "-it" else "-i" ]
 		(shim : params)
 	r <- withHandle StdoutHandle createProcessSuccess p $
-		processoutput Nothing
+		processChainOutput
 	when (r /= FailedChange) $
 		setProvisionedFlag cid 
 	return r
-  where
-	processoutput lastline h = do
-		v <- catchMaybeIO (hGetLine h)
-		case v of
-			Nothing -> pure $ fromMaybe FailedChange $
-				readish =<< lastline
-			Just s -> do
-				maybe noop putStrLn lastline
-				hFlush stdout
-				processoutput (Just s) h
 
 toChain :: ContainerId -> CmdLine
 toChain cid = DockerChain (containerHostName cid) (fromContainerId cid)
diff --git a/src/Propellor/Property/Systemd.hs b/src/Propellor/Property/Systemd.hs
new file mode 100644
index 00000000..be08a847
--- /dev/null
+++ b/src/Propellor/Property/Systemd.hs
@@ -0,0 +1,103 @@
+module Propellor.Property.Systemd (
+	installed,
+	persistentJournal,
+	container,
+	nspawned,
+) where
+
+import Propellor
+import qualified Propellor.Property.Chroot as Chroot
+import qualified Propellor.Property.Apt as Apt
+import Utility.SafeCommand
+
+import Data.List.Utils
+
+type MachineName = String
+
+type NspawnParam = CommandParam
+
+data Container = Container MachineName System [CommandParam] Host
+
+instance Hostlike Container where
+        (Container n s ps h) & p = Container n s ps (h & p)
+        (Container n s ps h) &^ p = Container n s ps (h &^ p)
+        getHost (Container _ _ _ h) = h
+
+-- dbus is only a Recommends of systemd, but is needed for communication
+-- from the systemd inside a container to the one outside, so make sure it
+-- gets installed.
+installed :: Property
+installed = Apt.installed ["systemd", "dbus"]
+
+-- | Sets up persistent storage of the journal.
+persistentJournal :: Property
+persistentJournal = check (not <$> doesDirectoryExist dir) $ 
+	combineProperties "persistent systetemd journal"
+		[ cmdProperty "install" ["-d", "-g", "systemd-journal", dir]
+		, cmdProperty "setfacl" ["-R", "-nm", "g:adm:rx,d:g:adm:rx", dir]
+		]
+		`requires` Apt.installed ["acl"]
+  where
+	dir = "/var/log/journal"
+
+-- | Defines a container with a given machine name, containing the specified
+-- System. Properties can be added to configure the Container.
+--
+-- > container "webserver" (System (Debian Unstable) "amd64") []
+container :: MachineName -> System -> [NspawnParam] -> Container
+container name system ps = Container name system ps (Host name [] mempty)
+
+-- | Runs a container using systemd-nspawn.
+--
+-- A systemd unit is set up for the container, so it will automatically
+-- be started on boot.
+--
+-- Systemd is automatically installed inside the container, and will
+-- communicate with the host's systemd. This allows systemctl to be used to
+-- examine the status of services running inside the container.
+--
+-- When the host system has persistentJournal enabled, journactl can be
+-- used to examine logs forwarded from the container.
+--
+-- Reverting this property stops the container, removes the systemd unit,
+-- and deletes the chroot and all its contents.
+nspawned :: Container -> RevertableProperty
+nspawned c@(Container name system _ h) = RevertableProperty setup teardown
+  where
+	-- TODO after container is running, use nsenter to enter it
+	-- and run propellor to finish provisioning.
+	setup = toProp (nspawnService c)
+		`requires` toProp chrootprovisioned
+
+	teardown = toProp (revert (chrootprovisioned))
+		`requires` toProp (revert (nspawnService c))
+
+	-- When provisioning the chroot, pass a version of the Host
+	-- that only has the Property of systemd being installed.
+	-- This is to avoid starting any daemons in the chroot,
+	-- which would not run in the container's namespace.
+	chrootprovisioned = Chroot.provisioned $
+		Chroot.Chroot (containerDir name) system $
+			h { hostProperties = [installed] }
+
+nspawnService :: Container -> RevertableProperty
+nspawnService (Container name _ ps _) = RevertableProperty setup teardown
+  where
+	service = nspawnServiceName name
+	servicefile = "/etc/systemd/system/multi-user.target.wants" </> service
+
+	setup = check (not <$> doesFileExist servicefile) $
+		combineProperties ("container running " ++ service)
+			[ cmdProperty "systemctl" ["enable", service]
+			, cmdProperty "systemctl" ["start", service]
+			]
+
+	-- TODO adjust execStart line to reflect ps
+
+	teardown = undefined
+
+nspawnServiceName :: MachineName -> String
+nspawnServiceName name = "systemd-nspawn@" ++ name ++ ".service"
+
+containerDir :: MachineName -> FilePath
+containerDir name = "/var/lib/container" ++ replace "/" "_" name
diff --git a/src/Propellor/Property/Docker/Shim.hs b/src/Propellor/Shim.hs
index c2f35d0c..5b5aa68e 100644
--- a/src/Propellor/Property/Docker/Shim.hs
+++ b/src/Propellor/Shim.hs
@@ -1,9 +1,10 @@
--- | Support for running propellor, as built outside a docker container,
--- inside the container.
+-- | Support for running propellor, as built outside a container,
+-- inside the container, without needing to install anything into the
+-- container.
 --
 -- Note: This is currently Debian specific, due to glibcLibs.
 
-module Propellor.Property.Docker.Shim (setup, cleanEnv, file) where
+module Propellor.Shim (setup, cleanEnv, file) where
 
 import Propellor
 import Utility.LinuxMkLibs
diff --git a/src/Propellor/Types.hs b/src/Propellor/Types.hs
index 90c08e64..56eafc6d 100644
--- a/src/Propellor/Types.hs
+++ b/src/Propellor/Types.hs
@@ -25,6 +25,7 @@ module Propellor.Types
 	, fromVal
 	, DockerInfo(..)
 	, DockerRunParam(..)
+	, ChrootInfo(..)
 	, module Propellor.Types.OS
 	, module Propellor.Types.Dns
 	) where
@@ -154,6 +155,7 @@ data CmdLine
 	| Update HostName
 	| DockerInit HostName
 	| DockerChain HostName String
+	| ChrootChain HostName FilePath
 	| GitPush Fd Fd
 	deriving (Read, Show, Eq)
 
@@ -166,11 +168,12 @@ data Info = Info
 	, _dns :: S.Set Dns.Record
 	, _namedconf :: Dns.NamedConfMap
 	, _dockerinfo :: DockerInfo
+	, _chrootinfo :: ChrootInfo
 	}
-	deriving (Eq, Show)
+	deriving (Show)
 
 instance Monoid Info where
-	mempty = Info mempty mempty mempty mempty mempty mempty mempty
+	mempty = Info mempty mempty mempty mempty mempty mempty mempty mempty
 	mappend old new = Info
 		{ _os = _os old <> _os new
 		, _privDataFields = _privDataFields old <> _privDataFields new
@@ -179,6 +182,7 @@ instance Monoid Info where
 		, _dns = _dns old <> _dns new
 		, _namedconf = _namedconf old <> _namedconf new
 		, _dockerinfo = _dockerinfo old <> _dockerinfo new
+		, _chrootinfo = _chrootinfo old <> _chrootinfo new
 		}
 
 data Val a = Val a | NoVal
@@ -207,13 +211,18 @@ instance Monoid DockerInfo where
 		, _dockerContainers = M.union (_dockerContainers old) (_dockerContainers new)
 		}
 
-instance Eq DockerInfo where
-	x == y = and
-		[ let simpl v = map (\(DockerRunParam a) -> a "") (_dockerRunParams v)
-		  in simpl x == simpl y
-		]
-
 newtype DockerRunParam = DockerRunParam (HostName -> String)
 
 instance Show DockerRunParam where
 	show (DockerRunParam a) = a ""
+
+data ChrootInfo = ChrootInfo
+	{ _chroots :: M.Map FilePath Host
+	}
+	deriving (Show)
+
+instance Monoid ChrootInfo where
+	mempty = ChrootInfo mempty
+	mappend old new = ChrootInfo
+		{ _chroots = M.union (_chroots old) (_chroots new)
+		}