diff --git a/archiso/initcpio/hooks/archiso b/archiso/initcpio/hooks/archiso
index 9d38f07..fcfe820 100644
--- a/archiso/initcpio/hooks/archiso
+++ b/archiso/initcpio/hooks/archiso
@@ -17,7 +17,7 @@ _mnt_dmsnapshot() {
             msg ":: Found '/run/archiso/cowspace/${cow_directory}/${img_name}.cow', using as persistent."
         else
             msg ":: Creating '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' as persistent."
-            truncate -s "${cowfile_size}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
+            truncate -s "${cow_spacesize}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
         fi
     else
         if [[ -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow" ]]; then
@@ -25,7 +25,7 @@ _mnt_dmsnapshot() {
             rm -f "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
         fi
         msg ":: Creating '/run/archiso/cowspace/${cow_directory}/${img_name}.cow' as non-persistent."
-        truncate -s "${cowfile_size}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
+        truncate -s "${cow_spacesize}" "/run/archiso/cowspace/${cow_directory}/${img_name}.cow"
     fi
 
     rw_dev=$(losetup --find --show "/run/archiso/cowspace/${cow_directory}/${img_name}.cow")
@@ -110,7 +110,7 @@ run_hook() {
     [[ -z "${archisobasedir}" ]] && archisobasedir="arch"
     [[ -z "${dm_snap_prefix}" ]] && dm_snap_prefix="arch"
     [[ -z "${archisodevice}" ]] && archisodevice="/dev/disk/by-label/${archisolabel}"
-    [[ -z "${cowfile_size}" ]] && cowfile_size="256M"
+    [[ -z "${cow_spacesize}" ]] && cow_spacesize="256M"
 
     if [[ -n "${cow_label}" ]]; then
         cow_device="/dev/disk/by-label/${cow_label}"
@@ -168,9 +168,9 @@ archiso_mount_handler() {
         echo $(readlink -f ${cow_device}) >> /run/archiso/used_block_devices
         mount -o remount,rw "/run/archiso/cowspace"
     else
-        msg ":: Mounting /run/archiso/cowspace (tmpfs) filesystem, size=${cowfile_size}..."
+        msg ":: Mounting /run/archiso/cowspace (tmpfs) filesystem, size=${cow_spacesize}..."
         mkdir -p /run/archiso/cowspace
-        mount -t tmpfs -o "size=${cowfile_size}",mode=0755 cowspace /run/archiso/cowspace
+        mount -t tmpfs -o "size=${cow_spacesize}",mode=0755 cowspace /run/archiso/cowspace
     fi
     mkdir -p "/run/archiso/cowspace/${cow_directory}"
 
diff --git a/docs/README.bootparams b/docs/README.bootparams
index 4c324f2..356375d 100644
--- a/docs/README.bootparams
+++ b/docs/README.bootparams
@@ -30,17 +30,18 @@ INDEX
                     performs a self-test of all files inside ${install_dir},
                     and continue booting if ok.
                     Default: (unset)
-* cow_label=        Set the filesystem label where COW (dm-snapshot)
-                    file must be stored.
+* cow_label=        Set the filesystem label where COW file (for dm-snapshot)
+                    or upperdir/workdir files (for overlayfs) must be stored.
                     Default: (unset)
-* cow_device=       Set the device node where COW (dm-snapshot) file
-                    must be stored.
+* cow_device=       Like cow_label= but using device node.
                     Default: (unset) or "/dev/disk/by-label/${cow_label}"
 * cow_directory=    Set a directory inside ${cow_device}.
                     Default: "/persistent_${archisolabel}/${arch}"
 * cow_persistent=   Set if snapshot is persistent "P" or non-persistent "N".
+                    Only used for dm-snapshot mode, ignored for overlayfs.
                     Default: "N" (if no ${cow_device} is used) otherwise "P".
-* cowfile_size=     Set the size for COW file (dm-snapshot).
+* cow_spacesize=    Set the size for COW space (tmpfs). Valid for both
+                    dm-snapshot and overlayfs mode.
                     The argument is an integer and optional unit.
                     Units are M,G (powers of 1024).
                     Default: "256M"
@@ -52,7 +53,8 @@ INDEX
                     Size is in bytes (suffix with "k", "m" and "g") or
                     in percentage of available RAM.
                     Default: "75%"
-* dm_snap_prefix=   Set a prefix for device-mapper snapshot node names.
+* dm_snap_prefix=   Set a prefix for dm-snapshot node names.
+                    Only used for dm-snapshot mode, ignored for overlayfs.
                     Default: "arch"
 * arch=             Force an architecture type (i686 | x86_64).
                     Do not set it for normal operations.