diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,15 @@
+propellor (4.5.0) unstable; urgency=medium
+
+  * Generalized the PartSpec DSL, so it can be used for both
+    disk image partitioning, and disk device partitioning, with
+    different partition sizing methods as appropriate for the different
+    uses. (minor API change)
+  * Propellor.Property.Parted: Added calcPartTable function which uses
+    PartSpec DiskPart, and a useDiskSpace combinator.
+  * Generate a better description for versioned properties.
+
+ -- Joey Hess <id@joeyh.name>  Fri, 21 Jul 2017 16:40:13 -0400
+
 propellor (4.4.0) unstable; urgency=medium
 
   * Propellor.Property.Timezone: New module, contributed by Sean Whitton.
diff --git a/debian/changelog b/debian/changelog
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,15 @@
+propellor (4.5.0) unstable; urgency=medium
+
+  * Generalized the PartSpec DSL, so it can be used for both
+    disk image partitioning, and disk device partitioning, with
+    different partition sizing methods as appropriate for the different
+    uses. (minor API change)
+  * Propellor.Property.Parted: Added calcPartTable function which uses
+    PartSpec DiskPart, and a useDiskSpace combinator.
+  * Generate a better description for versioned properties.
+
+ -- Joey Hess <id@joeyh.name>  Fri, 21 Jul 2017 16:40:13 -0400
+
 propellor (4.4.0) unstable; urgency=medium
 
   * Propellor.Property.Timezone: New module, contributed by Sean Whitton.
diff --git a/joeyconfig.hs b/joeyconfig.hs
--- a/joeyconfig.hs
+++ b/joeyconfig.hs
@@ -83,6 +83,8 @@
 	& ipv6 "2001:4830:1600:187::2"
 	& Aiccu.hasConfig "T18376" "JHZ2-SIXXS"
 
+	& User.nuked (User "nosuchuser") User.YesReallyDeleteHome
+
 	& JoeySites.dkimMilter
 	& JoeySites.postfixSaslPasswordClient
 	-- & JoeySites.alarmClock "*-*-* 7:30" (User "joey")
diff --git a/propellor.cabal b/propellor.cabal
--- a/propellor.cabal
+++ b/propellor.cabal
@@ -1,5 +1,5 @@
 Name: propellor
-Version: 4.4.0
+Version: 4.5.0
 Cabal-Version: >= 1.20
 License: BSD2
 Maintainer: Joey Hess <id@joeyh.name>
@@ -135,6 +135,7 @@
     Propellor.Property.OS
     Propellor.Property.Pacman
     Propellor.Property.Parted
+    Propellor.Property.Parted.Types
     Propellor.Property.Partition
     Propellor.Property.Postfix
     Propellor.Property.PropellorRepo
@@ -193,6 +194,7 @@
     Propellor.Types.Info
     Propellor.Types.MetaTypes
     Propellor.Types.OS
+    Propellor.Types.PartSpec
     Propellor.Types.PrivData
     Propellor.Types.Result
     Propellor.Types.ResultCheck
diff --git a/src/Propellor/Property/DiskImage.hs b/src/Propellor/Property/DiskImage.hs
--- a/src/Propellor/Property/DiskImage.hs
+++ b/src/Propellor/Property/DiskImage.hs
@@ -20,12 +20,12 @@
 import Propellor.Property.DiskImage.PartSpec
 import Propellor.Property.Chroot (Chroot)
 import Propellor.Property.Chroot.Util (removeChroot)
+import Propellor.Property.Mount
 import qualified Propellor.Property.Chroot as Chroot
 import qualified Propellor.Property.Grub as Grub
 import qualified Propellor.Property.File as File
 import qualified Propellor.Property.Apt as Apt
 import Propellor.Property.Parted
-import Propellor.Property.Mount
 import Propellor.Property.Fstab (SwapPartition(..), genFstab)
 import Propellor.Property.Partition
 import Propellor.Property.Rsync
@@ -34,7 +34,7 @@
 import Propellor.Container
 import Utility.Path
 
-import Data.List (isPrefixOf, isInfixOf, sortBy)
+import Data.List (isPrefixOf, isInfixOf, sortBy, unzip4)
 import Data.Function (on)
 import qualified Data.Map.Strict as M
 import qualified Data.ByteString.Lazy as L
@@ -109,16 +109,16 @@
 -- >	& Apt.installed ["linux-image-amd64"]
 -- >	& Grub.installed PC
 -- >	& hasPassword (User "root")
-imageBuilt :: DiskImage -> (FilePath -> Chroot) -> TableType -> [PartSpec] -> RevertableProperty (HasInfo + DebianLike) Linux
+imageBuilt :: DiskImage -> (FilePath -> Chroot) -> TableType -> [PartSpec ()] -> RevertableProperty (HasInfo + DebianLike) Linux
 imageBuilt = imageBuilt' False
 
 -- | Like 'built', but the chroot is deleted and rebuilt from scratch each
 -- time. This is more expensive, but useful to ensure reproducible results
 -- when the properties of the chroot have been changed.
-imageRebuilt :: DiskImage -> (FilePath -> Chroot) -> TableType -> [PartSpec] -> RevertableProperty (HasInfo + DebianLike) Linux
+imageRebuilt :: DiskImage -> (FilePath -> Chroot) -> TableType -> [PartSpec ()] -> RevertableProperty (HasInfo + DebianLike) Linux
 imageRebuilt = imageBuilt' True
 
-imageBuilt' :: Bool -> DiskImage -> (FilePath -> Chroot) -> TableType -> [PartSpec] -> RevertableProperty (HasInfo + DebianLike) Linux
+imageBuilt' :: Bool -> DiskImage -> (FilePath -> Chroot) -> TableType -> [PartSpec ()] -> RevertableProperty (HasInfo + DebianLike) Linux
 imageBuilt' rebuild img mkchroot tabletype partspec =
 	imageBuiltFrom img chrootdir tabletype final partspec
 		`requires` Chroot.provisioned chroot
@@ -159,13 +159,13 @@
 	skipit = doNothing :: Property UnixLike
 
 -- | Builds a disk image from the contents of a chroot.
-imageBuiltFrom :: DiskImage -> FilePath -> TableType -> Finalization -> [PartSpec] -> RevertableProperty (HasInfo + DebianLike) UnixLike
+imageBuiltFrom :: DiskImage -> FilePath -> TableType -> Finalization -> [PartSpec ()] -> RevertableProperty (HasInfo + DebianLike) UnixLike
 imageBuiltFrom img chrootdir tabletype final partspec = mkimg <!> rmimg
   where
 	desc = img ++ " built from " ++ chrootdir
 	mkimg = property' desc $ \w -> do
-		-- unmount helper filesystems such as proc from the chroot
-		-- before getting sizes
+		-- Unmount helper filesystems such as proc from the chroot
+		-- first; don't want to include the contents of those.
 		liftIO $ unmountBelow chrootdir
 		szm <- M.mapKeys (toSysDir chrootdir) . M.map toPartSize
 			<$> liftIO (dirSizes chrootdir)
@@ -214,10 +214,10 @@
 
 -- The constructor for each Partition is passed the size of the files
 -- from the chroot that will be put in that partition.
-fitChrootSize :: TableType -> [PartSpec] -> [PartSize] -> ([Maybe MountPoint], [MountOpts], PartTable)
+fitChrootSize :: TableType -> [PartSpec ()] -> [PartSize] -> ([Maybe MountPoint], [MountOpts], PartTable)
 fitChrootSize tt l basesizes = (mounts, mountopts, parttable)
   where
-	(mounts, mountopts, sizers) = unzip3 l
+	(mounts, mountopts, sizers, _) = unzip4 l
 	parttable = PartTable tt (zipWith id sizers basesizes)
 
 -- | Generates a map of the sizes of the contents of
diff --git a/src/Propellor/Property/DiskImage/PartSpec.hs b/src/Propellor/Property/DiskImage/PartSpec.hs
--- a/src/Propellor/Property/DiskImage/PartSpec.hs
+++ b/src/Propellor/Property/DiskImage/PartSpec.hs
@@ -1,32 +1,24 @@
 -- | Disk image partition specification and combinators.
 
+-- Partitions in disk images default to being sized large enough to hold
+-- the files that appear in the directory where the partition is to be
+-- mounted. Plus a fudge factor, since filesystems have some space
+-- overhead.
+
 module Propellor.Property.DiskImage.PartSpec (
+	module Propellor.Types.PartSpec,
 	module Propellor.Property.DiskImage.PartSpec,
-	Partition,
-	PartSize(..),
-	PartFlag(..),
-	TableType(..),
-	Fs(..),
-	MountPoint,
 ) where
 
 import Propellor.Base
 import Propellor.Property.Parted
-import Propellor.Property.Mount
-
--- | Specifies a mount point, mount options, and a constructor for a Partition.
--- 
--- The size that is eventually provided is the amount of space needed to 
--- hold the files that appear in the directory where the partition is to be
--- mounted. Plus a fudge factor, since filesystems have some space
--- overhead.
-type PartSpec = (Maybe MountPoint, MountOpts, PartSize -> Partition)
+import Propellor.Types.PartSpec
 
--- | Partitions that are not to be mounted (ie, LinuxSwap), or that have
--- no corresponding directory in the chroot will have 128 MegaBytes
--- provided as a default size.
-defSz :: PartSize
-defSz = MegaBytes 128
+-- | Adds additional free space to the partition.
+addFreeSpace :: PartSpec t -> PartSize -> PartSpec t
+addFreeSpace (mp, o, p, t) freesz = (mp, o, p', t)
+  where
+	p' = \sz -> p (sz <> freesz)
 
 -- | Add 2% for filesystem overhead. Rationalle for picking 2%:
 -- A filesystem with 1% overhead might just sneak by as acceptable.
@@ -35,55 +27,3 @@
 -- Add an additional 200 mb for temp files, journals, etc.
 fudge :: PartSize -> PartSize
 fudge (MegaBytes n) = MegaBytes (n + n `div` 100 * 2 + 3 + 200)
-
--- | Specifies a swap partition of a given size.
-swapPartition :: PartSize -> PartSpec
-swapPartition sz = (Nothing, mempty, const (mkPartition LinuxSwap sz))
-
--- | Specifies a partition with a given filesystem.
---
--- The partition is not mounted anywhere by default; use the combinators
--- below to configure it.
-partition :: Fs -> PartSpec
-partition fs = (Nothing, mempty, mkPartition fs)
-
--- | Specifies where to mount a partition.
-mountedAt :: PartSpec -> FilePath -> PartSpec
-mountedAt (_, o, p) mp = (Just mp, o, p)
-
--- | Specifies a mount option, such as "noexec"
-mountOpt :: ToMountOpts o => PartSpec -> o -> PartSpec
-mountOpt (mp, o, p) o' = (mp, o <> toMountOpts o', p)
-
--- | Mount option to make a partition be remounted readonly when there's an
--- error accessing it.
-errorReadonly :: MountOpts
-errorReadonly = toMountOpts "errors=remount-ro"
-
--- | Adds additional free space to the partition.
-addFreeSpace :: PartSpec -> PartSize -> PartSpec
-addFreeSpace (mp, o, p) freesz = (mp, o, \sz -> p (sz <> freesz))
-
--- | Forced a partition to be a specific size, instead of scaling to the
--- size needed for the files in the chroot.
-setSize :: PartSpec -> PartSize -> PartSpec
-setSize (mp, o, p) sz = (mp, o, const (p sz))
-
--- | Sets the percent of the filesystem blocks reserved for the super-user.
---
--- The default is 5% for ext2 and ext4. Some filesystems may not support
--- this.
-reservedSpacePercentage :: PartSpec -> Int -> PartSpec
-reservedSpacePercentage s percent = adjustp s $ \p -> 
-	p { partMkFsOpts = ("-m"):show percent:partMkFsOpts p }
-
--- | Sets a flag on the partition.
-setFlag :: PartSpec -> PartFlag -> PartSpec
-setFlag s f = adjustp s $ \p -> p { partFlags = (f, True):partFlags p }
-
--- | Makes a MSDOS partition be Extended, rather than Primary.
-extended :: PartSpec -> PartSpec
-extended s = adjustp s $ \p -> p { partType = Extended }
-
-adjustp :: PartSpec -> (Partition -> Partition) -> PartSpec
-adjustp (mp, o, p) f = (mp, o, f . p)
diff --git a/src/Propellor/Property/Parted.hs b/src/Propellor/Property/Parted.hs
--- a/src/Propellor/Property/Parted.hs
+++ b/src/Propellor/Property/Parted.hs
@@ -1,6 +1,7 @@
 {-# LANGUAGE FlexibleContexts #-}
 
 module Propellor.Property.Parted (
+	-- * Types
 	TableType(..),
 	PartTable(..),
 	partTableSize,
@@ -15,137 +16,30 @@
 	Partition.MkfsOpts,
 	PartType(..),
 	PartFlag(..),
-	Eep(..),
+	-- * Properties
 	partitioned,
 	parted,
+	Eep(..),
 	installed,
+	-- * PartSpec combinators
+	calcPartTable,
+	DiskSize(..),
+	DiskPart,
+	module Propellor.Types.PartSpec,
+	DiskSpaceUse(..),
+	useDiskSpace,
 ) where
 
 import Propellor.Base
+import Propellor.Property.Parted.Types
 import qualified Propellor.Property.Apt as Apt
 import qualified Propellor.Property.Pacman as Pacman
 import qualified Propellor.Property.Partition as Partition
+import Propellor.Types.PartSpec
 import Utility.DataUnits
-import Data.Char
-import System.Posix.Files
 
-class PartedVal a where
-	pval :: a -> String
-
--- | Types of partition tables supported by parted.
-data TableType = MSDOS | GPT | AIX | AMIGA | BSD | DVH | LOOP | MAC | PC98 | SUN
-	deriving (Show)
-
-instance PartedVal TableType where
-	pval = map toLower . show
-
--- | A disk's partition table.
-data PartTable = PartTable TableType [Partition]
-	deriving (Show)
-
-instance Monoid PartTable where
-	-- | default TableType is MSDOS
-	mempty = PartTable MSDOS []
-	-- | uses the TableType of the second parameter
-	mappend (PartTable _l1 ps1) (PartTable l2 ps2) = PartTable l2 (ps1 ++ ps2)
-
--- | Gets the total size of the disk specified by the partition table.
-partTableSize :: PartTable -> ByteSize
-partTableSize (PartTable _ ps) = fromPartSize $
-	-- add 1 megabyte to hold the partition table itself
-	mconcat (MegaBytes 1 : map partSize ps)
-
--- | A partition on the disk.
-data Partition = Partition
-	{ partType :: PartType
-	, partSize :: PartSize
-	, partFs :: Partition.Fs
-	, partMkFsOpts :: Partition.MkfsOpts
-	, partFlags :: [(PartFlag, Bool)] -- ^ flags can be set or unset (parted may set some flags by default)
-	, partName :: Maybe String -- ^ optional name for partition (only works for GPT, PC98, MAC)
-	}
-	deriving (Show)
-
--- | Makes a Partition with defaults for non-important values.
-mkPartition :: Partition.Fs -> PartSize -> Partition
-mkPartition fs sz = Partition
-	{ partType = Primary
-	, partSize = sz
-	, partFs = fs
-	, partMkFsOpts = []
-	, partFlags = []
-	, partName = Nothing
-	}
-
--- | Type of a partition.
-data PartType = Primary | Logical | Extended
-	deriving (Show)
-
-instance PartedVal PartType where
-	pval Primary = "primary"
-	pval Logical = "logical"
-	pval Extended = "extended"
-
--- | All partition sizing is done in megabytes, so that parted can
--- automatically lay out the partitions.
---
--- Note that these are SI megabytes, not mebibytes.
-newtype PartSize = MegaBytes Integer
-	deriving (Show)
-
-instance PartedVal PartSize where
-	pval (MegaBytes n)
-		| n > 0 = val n ++ "MB"
-		-- parted can't make partitions smaller than 1MB;
-		-- avoid failure in edge cases
-		| otherwise = "1MB"
-
--- | Rounds up to the nearest MegaByte.
-toPartSize :: ByteSize -> PartSize
-toPartSize b = MegaBytes $ ceiling (fromInteger b / 1000000 :: Double)
-
-fromPartSize :: PartSize -> ByteSize
-fromPartSize (MegaBytes b) = b * 1000000
-
-instance Monoid PartSize where
-	mempty = MegaBytes 0
-	mappend (MegaBytes a) (MegaBytes b) = MegaBytes (a + b)
-
-reducePartSize :: PartSize -> PartSize -> PartSize
-reducePartSize (MegaBytes a) (MegaBytes b) = MegaBytes (a - b)
-
--- | Flags that can be set on a partition.
-data PartFlag = BootFlag | RootFlag | SwapFlag | HiddenFlag | RaidFlag | LvmFlag | LbaFlag | LegacyBootFlag | IrstFlag | EspFlag | PaloFlag
-	deriving (Show)
-
-instance PartedVal PartFlag where
-	pval BootFlag = "boot"
-	pval RootFlag = "root"
-	pval SwapFlag = "swap"
-	pval HiddenFlag = "hidden"
-	pval RaidFlag = "raid"
-	pval LvmFlag = "lvm"
-	pval LbaFlag = "lba"
-	pval LegacyBootFlag = "legacy_boot"
-	pval IrstFlag = "irst"
-	pval EspFlag = "esp"
-	pval PaloFlag = "palo"
-
-instance PartedVal Bool where
-	pval True = "on"
-	pval False = "off"
-
-instance PartedVal Partition.Fs where
-	pval Partition.EXT2 = "ext2"
-	pval Partition.EXT3 = "ext3"
-	pval Partition.EXT4 = "ext4"
-	pval Partition.BTRFS = "btrfs"
-	pval Partition.REISERFS = "reiserfs"
-	pval Partition.XFS = "xfs"
-	pval Partition.FAT = "fat"
-	pval Partition.VFAT = "vfat"
-	pval Partition.NTFS = "ntfs"
-	pval Partition.LinuxSwap = "linux-swap"
+import System.Posix.Files
+import Data.List (genericLength)
 
 data Eep = YesReallyDeleteDiskContents
 
@@ -202,3 +96,67 @@
 -- | Gets parted installed.
 installed :: Property (DebianLike + ArchLinux)
 installed = Apt.installed ["parted"] `pickOS` Pacman.installed ["parted"]
+
+-- | Gets the total size of the disk specified by the partition table.
+partTableSize :: PartTable -> ByteSize
+partTableSize (PartTable _ ps) = fromPartSize $
+	mconcat (partitionTableOverhead : map partSize ps)
+
+-- | Some disk is used to store the partition table itself. Assume less
+-- than 1 mb.
+partitionTableOverhead :: PartSize
+partitionTableOverhead = MegaBytes 1
+
+-- | Calculate a partition table, for a given size of disk.
+--
+-- For example:
+--
+-- >	calcPartTable (1024 * 1024 * 1024 * 100) MSDOS
+-- > 		[ partition EXT2 `mountedAt` "/boot"
+-- > 			`setSize` MegaBytes 256
+-- > 			`setFlag` BootFlag
+-- >		, partition EXT4 `mountedAt` "/"
+-- >			`useDisk` RemainingSpace
+-- >		]
+calcPartTable :: DiskSize -> TableType -> [PartSpec DiskPart] -> PartTable
+calcPartTable (DiskSize disksize) tt l = PartTable tt (map go l)
+  where
+	go (_, _, mkpart, FixedDiskPart) = mkpart defSz
+	go (_, _, mkpart, DynamicDiskPart (Percent p)) = mkpart $ toPartSize $
+		diskremainingafterfixed * fromIntegral p `div` 100
+	go (_, _, mkpart, DynamicDiskPart RemainingSpace) = mkpart $ toPartSize $
+		diskremaining `div` genericLength (filter isremainingspace l)
+	diskremainingafterfixed = 
+		disksize - sumsizes (filter isfixed l)
+	diskremaining =
+		disksize - sumsizes (filter (not . isremainingspace) l)
+	sumsizes = sum . map fromPartSize . (partitionTableOverhead :) .
+		map (partSize . go)
+	isfixed (_, _, _, FixedDiskPart) = True
+	isfixed _ = False
+	isremainingspace (_, _, _, DynamicDiskPart RemainingSpace) = True
+	isremainingspace _ = False
+
+-- | Size of a disk, in bytes.
+newtype DiskSize = DiskSize ByteSize
+	deriving (Show)
+
+data DiskPart = FixedDiskPart | DynamicDiskPart DiskSpaceUse
+
+data DiskSpaceUse = Percent Int | RemainingSpace
+
+instance Monoid DiskPart
+  where
+	mempty = FixedDiskPart
+	mappend FixedDiskPart FixedDiskPart = FixedDiskPart
+	mappend (DynamicDiskPart (Percent a)) (DynamicDiskPart (Percent b)) = DynamicDiskPart (Percent (a + b))
+	mappend (DynamicDiskPart RemainingSpace) (DynamicDiskPart RemainingSpace) = DynamicDiskPart RemainingSpace
+	mappend (DynamicDiskPart (Percent a)) _ = DynamicDiskPart (Percent a)
+	mappend _ (DynamicDiskPart (Percent b)) = DynamicDiskPart (Percent b)
+	mappend (DynamicDiskPart RemainingSpace) _ = DynamicDiskPart RemainingSpace
+	mappend _ (DynamicDiskPart RemainingSpace) = DynamicDiskPart RemainingSpace
+
+-- | Make a partition use some percentage of the size of the disk
+-- (less all fixed size partitions), or the remaining space in the disk.
+useDiskSpace :: PartSpec DiskPart -> DiskSpaceUse -> PartSpec DiskPart
+useDiskSpace (mp, o, p, _) diskuse = (mp, o, p, DynamicDiskPart diskuse)
diff --git a/src/Propellor/Property/Parted/Types.hs b/src/Propellor/Property/Parted/Types.hs
new file mode 100644
--- /dev/null
+++ b/src/Propellor/Property/Parted/Types.hs
@@ -0,0 +1,119 @@
+module Propellor.Property.Parted.Types where
+
+import Propellor.Base
+import qualified Propellor.Property.Partition as Partition
+import Utility.DataUnits
+
+import Data.Char
+
+class PartedVal a where
+	pval :: a -> String
+
+-- | Types of partition tables supported by parted.
+data TableType = MSDOS | GPT | AIX | AMIGA | BSD | DVH | LOOP | MAC | PC98 | SUN
+	deriving (Show)
+
+instance PartedVal TableType where
+	pval = map toLower . show
+
+-- | A disk's partition table.
+data PartTable = PartTable TableType [Partition]
+	deriving (Show)
+
+instance Monoid PartTable where
+	-- | default TableType is MSDOS
+	mempty = PartTable MSDOS []
+	-- | uses the TableType of the second parameter
+	mappend (PartTable _l1 ps1) (PartTable l2 ps2) = PartTable l2 (ps1 ++ ps2)
+
+-- | A partition on the disk.
+data Partition = Partition
+	{ partType :: PartType
+	, partSize :: PartSize
+	, partFs :: Partition.Fs
+	, partMkFsOpts :: Partition.MkfsOpts
+	, partFlags :: [(PartFlag, Bool)] -- ^ flags can be set or unset (parted may set some flags by default)
+	, partName :: Maybe String -- ^ optional name for partition (only works for GPT, PC98, MAC)
+	}
+	deriving (Show)
+
+-- | Makes a Partition with defaults for non-important values.
+mkPartition :: Partition.Fs -> PartSize -> Partition
+mkPartition fs sz = Partition
+	{ partType = Primary
+	, partSize = sz
+	, partFs = fs
+	, partMkFsOpts = []
+	, partFlags = []
+	, partName = Nothing
+	}
+
+-- | Type of a partition.
+data PartType = Primary | Logical | Extended
+	deriving (Show)
+
+instance PartedVal PartType where
+	pval Primary = "primary"
+	pval Logical = "logical"
+	pval Extended = "extended"
+
+-- | All partition sizing is done in megabytes, so that parted can
+-- automatically lay out the partitions.
+--
+-- Note that these are SI megabytes, not mebibytes.
+newtype PartSize = MegaBytes Integer
+	deriving (Show)
+
+instance PartedVal PartSize where
+	pval (MegaBytes n)
+		| n > 0 = val n ++ "MB"
+		-- parted can't make partitions smaller than 1MB;
+		-- avoid failure in edge cases
+		| otherwise = "1MB"
+
+-- | Rounds up to the nearest MegaByte.
+toPartSize :: ByteSize -> PartSize
+toPartSize b = MegaBytes $ ceiling (fromInteger b / 1000000 :: Double)
+
+fromPartSize :: PartSize -> ByteSize
+fromPartSize (MegaBytes b) = b * 1000000
+
+instance Monoid PartSize where
+	mempty = MegaBytes 0
+	mappend (MegaBytes a) (MegaBytes b) = MegaBytes (a + b)
+
+reducePartSize :: PartSize -> PartSize -> PartSize
+reducePartSize (MegaBytes a) (MegaBytes b) = MegaBytes (a - b)
+
+-- | Flags that can be set on a partition.
+data PartFlag = BootFlag | RootFlag | SwapFlag | HiddenFlag | RaidFlag | LvmFlag | LbaFlag | LegacyBootFlag | IrstFlag | EspFlag | PaloFlag
+	deriving (Show)
+
+instance PartedVal PartFlag where
+	pval BootFlag = "boot"
+	pval RootFlag = "root"
+	pval SwapFlag = "swap"
+	pval HiddenFlag = "hidden"
+	pval RaidFlag = "raid"
+	pval LvmFlag = "lvm"
+	pval LbaFlag = "lba"
+	pval LegacyBootFlag = "legacy_boot"
+	pval IrstFlag = "irst"
+	pval EspFlag = "esp"
+	pval PaloFlag = "palo"
+
+instance PartedVal Bool where
+	pval True = "on"
+	pval False = "off"
+
+instance PartedVal Partition.Fs where
+	pval Partition.EXT2 = "ext2"
+	pval Partition.EXT3 = "ext3"
+	pval Partition.EXT4 = "ext4"
+	pval Partition.BTRFS = "btrfs"
+	pval Partition.REISERFS = "reiserfs"
+	pval Partition.XFS = "xfs"
+	pval Partition.FAT = "fat"
+	pval Partition.VFAT = "vfat"
+	pval Partition.NTFS = "ntfs"
+	pval Partition.LinuxSwap = "linux-swap"
diff --git a/src/Propellor/Property/Versioned.hs b/src/Propellor/Property/Versioned.hs
--- a/src/Propellor/Property/Versioned.hs
+++ b/src/Propellor/Property/Versioned.hs
@@ -55,7 +55,10 @@
 module Propellor.Property.Versioned (Versioned, version, (-->), (<|>)) where
 
 import Propellor
+import Propellor.Types.Core
 
+import Data.List
+
 -- | Something that has multiple versions of type `v`.
 type Versioned v t = VersionedBy v -> t
 
@@ -89,12 +92,21 @@
 	=> v
 	-> VerSpec v metatypes
 	-> RevertableProperty metatypes metatypes
-processVerSpec v (Base (c, p))
-	| c v = p
-	| otherwise = revert p
-processVerSpec v (More (c, p) vs)
-	| c v = processVerSpec v vs `before` p
-	| otherwise = revert p `before` processVerSpec v vs
+processVerSpec v s = combinedp s
+	`describe` intercalate " and " (combineddesc s [])
+  where
+	combinedp (Base (c, p))
+		| c v = p
+		| otherwise = revert p
+	combinedp (More (c, p) vs)
+		| c v = combinedp vs `before` p
+		| otherwise = revert p `before` combinedp vs
+	combineddesc (Base (c, p)) l
+		| c v = getDesc p : l
+		| otherwise = getDesc (revert p) : l
+	combineddesc (More (c, p) vs) l
+		| c v = getDesc p : combineddesc vs l
+		| otherwise = getDesc (revert p) : combineddesc vs l
 
 -- | Specify a function that checks the version, and what
 -- `RevertableProperty` to use if the version matches.
diff --git a/src/Propellor/Types/PartSpec.hs b/src/Propellor/Types/PartSpec.hs
new file mode 100644
--- /dev/null
+++ b/src/Propellor/Types/PartSpec.hs
@@ -0,0 +1,66 @@
+-- | Partition specification combinators.
+
+module Propellor.Types.PartSpec where
+
+import Propellor.Base
+import Propellor.Property.Parted.Types
+import Propellor.Property.Mount
+import Propellor.Property.Partition
+
+-- | Specifies a mount point, mount options, and a constructor for a
+-- Partition that determines its size.
+type PartSpec t = (Maybe MountPoint, MountOpts, PartSize -> Partition, t)
+
+-- | Specifies a partition with a given filesystem.
+--
+-- The partition is not mounted anywhere by default; use the combinators
+-- below to configure it.
+partition :: Monoid t => Fs -> PartSpec t
+partition fs = (Nothing, mempty, mkPartition fs, mempty)
+
+-- | Specifies a swap partition of a given size.
+swapPartition :: Monoid t => PartSize -> PartSpec t
+swapPartition sz = (Nothing, mempty, const (mkPartition LinuxSwap sz), mempty)
+
+-- | Specifies where to mount a partition.
+mountedAt :: PartSpec t -> FilePath -> PartSpec t
+mountedAt (_, o, p, t) mp = (Just mp, o, p, t)
+
+-- | Specify a fixed size for a partition.
+setSize :: PartSpec t -> PartSize -> PartSpec t
+setSize (mp, o, p, t) sz = (mp, o, const (p sz), t)
+
+-- | Specifies a mount option, such as "noexec"
+mountOpt :: ToMountOpts o => PartSpec t -> o -> PartSpec t
+mountOpt (mp, o, p, t) o' = (mp, o <> toMountOpts o', p, t)
+
+-- | Mount option to make a partition be remounted readonly when there's an
+-- error accessing it.
+errorReadonly :: MountOpts
+errorReadonly = toMountOpts "errors=remount-ro"
+
+-- | Sets the percent of the filesystem blocks reserved for the super-user.
+--
+-- The default is 5% for ext2 and ext4. Some filesystems may not support
+-- this.
+reservedSpacePercentage :: PartSpec t -> Int -> PartSpec t
+reservedSpacePercentage s percent = adjustp s $ \p -> 
+	p { partMkFsOpts = ("-m"):show percent:partMkFsOpts p }
+
+-- | Sets a flag on the partition.
+setFlag :: PartSpec t -> PartFlag -> PartSpec t
+setFlag s f = adjustp s $ \p -> p { partFlags = (f, True):partFlags p }
+
+-- | Makes a MSDOS partition be Extended, rather than Primary.
+extended :: PartSpec t -> PartSpec t
+extended s = adjustp s $ \p -> p { partType = Extended }
+
+adjustp :: PartSpec t -> (Partition -> Partition) -> PartSpec t
+adjustp (mp, o, p, t) f = (mp, o, f . p, t)
+
+adjustt :: PartSpec t -> (t -> t) -> PartSpec t
+adjustt (mp, o, p, t) f = (mp, o, p, f t)
+
+-- | Default partition size when not otherwize specified is 128 MegaBytes.
+defSz :: PartSize
+defSz = MegaBytes 128