diff --git a/Makefile.am b/Makefile.am
index 663958d7b..d37016cf4 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -307,7 +307,7 @@ ChangeLog: configure.ac
 # to DIST_SUBDIRS.
 docs/C_SOURCE_FILES: configure.ac
 	rm -f $@ $@-t
-	find $(DIST_SUBDIRS) -name '*.c' | \
+	find $(DIST_SUBDIRS) -name '*.[ch]' | \
 	grep -v -E '^(builder/index-parse.c|builder/index-scan.c|examples/|gnulib/|gobject/|perl/|tests/|test-data/)' | \
 	grep -v -E '/((guestfs|rc)_protocol\.c)$$' | \
 	grep -v -E '.*/errnostring\.c$$' | \
diff --git a/docs/C_SOURCE_FILES b/docs/C_SOURCE_FILES
index 028a64bf1..5b8350e8d 100644
--- a/docs/C_SOURCE_FILES
+++ b/docs/C_SOURCE_FILES
@@ -1,6 +1,8 @@
 align/scan.c
+builder/index-parse.h
 builder/index-parser-c.c
 builder/index-struct.c
+builder/index-struct.h
 builder/index-validate.c
 builder/pxzcat-c.c
 builder/setlocale-c.c
@@ -11,11 +13,13 @@ cat/log.c
 cat/ls.c
 cat/tail.c
 cat/visit.c
+cat/visit.h
 customize/crypt-c.c
 customize/dummy.c
 customize/perl_edit-c.c
 daemon/9p.c
 daemon/acl.c
+daemon/actions.h
 daemon/augeas.c
 daemon/available.c
 daemon/base64.c
@@ -26,12 +30,15 @@ daemon/btrfs.c
 daemon/cap.c
 daemon/checksum.c
 daemon/cleanups.c
+daemon/cleanups.h
 daemon/cmp.c
 daemon/command.c
+daemon/command.h
 daemon/compress.c
 daemon/copy.c
 daemon/cpio.c
 daemon/cpmv.c
+daemon/daemon.h
 daemon/dd.c
 daemon/debug-bmap.c
 daemon/debug.c
@@ -43,6 +50,7 @@ daemon/dmesg.c
 daemon/dropcaches.c
 daemon/du.c
 daemon/echo-daemon.c
+daemon/errnostring.h
 daemon/ext2.c
 daemon/fallocate.c
 daemon/file.c
@@ -56,6 +64,7 @@ daemon/fstrim.c
 daemon/glob.c
 daemon/grep.c
 daemon/grub.c
+daemon/guestfs_protocol.h
 daemon/guestfsd.c
 daemon/headtail.c
 daemon/hexdump.c
@@ -87,6 +96,7 @@ daemon/names.c
 daemon/ntfs.c
 daemon/ntfsclone.c
 daemon/optgroups.c
+daemon/optgroups.h
 daemon/parted.c
 daemon/pingdaemon.c
 daemon/proto.c
@@ -111,6 +121,7 @@ daemon/stubs-3.c
 daemon/stubs-4.c
 daemon/stubs-5.c
 daemon/stubs-6.c
+daemon/stubs.h
 daemon/swap.c
 daemon/sync.c
 daemon/syslinux.c
@@ -129,10 +140,14 @@ daemon/zero.c
 daemon/zerofree.c
 df/df.c
 df/domains.c
+df/domains.h
 df/estimate-max-threads.c
+df/estimate-max-threads.h
 df/main.c
 df/output.c
 df/parallel.c
+df/parallel.h
+df/virt-df.h
 dib/dummy.c
 diff/diff.c
 edit/edit.c
@@ -143,10 +158,12 @@ erlang/actions-3.c
 erlang/actions-4.c
 erlang/actions-5.c
 erlang/actions-6.c
+erlang/actions.h
 erlang/dispatch.c
 erlang/main.c
 erlang/structs.c
 fish/alloc.c
+fish/cmds-gperf.h
 fish/cmds.c
 fish/completion.c
 fish/config.c
@@ -154,6 +171,7 @@ fish/copy.c
 fish/decrypt.c
 fish/destpaths.c
 fish/display-options.c
+fish/display-options.h
 fish/display.c
 fish/domain.c
 fish/echo.c
@@ -168,7 +186,10 @@ fish/entries-6.c
 fish/event-names.c
 fish/events.c
 fish/file-edit.c
+fish/file-edit.h
+fish/fish-cmds.h
 fish/fish.c
+fish/fish.h
 fish/glob.c
 fish/help.c
 fish/hexedit.c
@@ -178,6 +199,7 @@ fish/lcd.c
 fish/man.c
 fish/more.c
 fish/options.c
+fish/options.h
 fish/prep-boot.c
 fish/prep-disk.c
 fish/prep-fs.c
@@ -185,8 +207,11 @@ fish/prep-lv.c
 fish/prep-part.c
 fish/prep.c
 fish/prepopts.c
+fish/prepopts.h
 fish/progress.c
+fish/progress.h
 fish/rc.c
+fish/rc_protocol.h
 fish/reopen.c
 fish/run-0.c
 fish/run-1.c
@@ -195,12 +220,15 @@ fish/run-3.c
 fish/run-4.c
 fish/run-5.c
 fish/run-6.c
+fish/run.h
 fish/setenv.c
 fish/supported.c
 fish/tilde.c
 fish/time.c
 fish/uri.c
+fish/uri.h
 fish/windows.c
+fish/windows.h
 format/format.c
 fuse/guestmount.c
 fuse/guestunmount.c
@@ -216,6 +244,7 @@ java/actions-3.c
 java/actions-4.c
 java/actions-5.c
 java/actions-6.c
+java/com_redhat_et_libguestfs_GuestFS.h
 java/handle.c
 lua/lua-guestfs.c
 make-fs/make-fs.c
@@ -232,19 +261,25 @@ mllib/uri-c.c
 ocaml/guestfs-c-actions.c
 ocaml/guestfs-c-errnos.c
 ocaml/guestfs-c.c
+ocaml/guestfs-c.h
 p2v/about-authors.c
 p2v/about-license.c
 p2v/config.c
 p2v/conversion.c
 p2v/gui.c
+p2v/inhibit.c
 p2v/kernel-cmdline.c
 p2v/kernel.c
 p2v/main.c
 p2v/miniexpect.c
+p2v/miniexpect.h
+p2v/p2v.h
 p2v/ssh.c
 p2v/utils.c
 p2v/whole-file.c
+php/extension/config.h
 php/extension/guestfs_php.c
+php/extension/php_guestfs_php.h
 python/actions-0.c
 python/actions-1.c
 python/actions-2.c
@@ -252,6 +287,7 @@ python/actions-3.c
 python/actions-4.c
 python/actions-5.c
 python/actions-6.c
+python/actions.h
 python/handle.c
 python/module.c
 python/structs.c
@@ -264,6 +300,8 @@ ruby/ext/guestfs/actions-3.c
 ruby/ext/guestfs/actions-4.c
 ruby/ext/guestfs/actions-5.c
 ruby/ext/guestfs/actions-6.c
+ruby/ext/guestfs/actions.h
+ruby/ext/guestfs/extconf.h
 ruby/ext/guestfs/handle.c
 ruby/ext/guestfs/module.c
 sparsify/dummy.c
@@ -288,12 +326,20 @@ src/copy-in-out.c
 src/create.c
 src/dbdump.c
 src/drives.c
+src/errnostring.h
 src/errors.c
 src/event-string.c
 src/events.c
 src/file.c
 src/filearch.c
 src/fuse.c
+src/guestfs-internal-actions.h
+src/guestfs-internal-all.h
+src/guestfs-internal-frontend-cleanups.h
+src/guestfs-internal-frontend.h
+src/guestfs-internal.h
+src/guestfs.h
+src/guestfs_protocol.h
 src/guid.c
 src/handle.c
 src/info.c
@@ -327,6 +373,7 @@ src/structs-compare.c
 src/structs-copy.c
 src/structs-free.c
 src/structs-print.c
+src/structs-print.h
 src/tmpdirs.c
 src/tsk.c
 src/uefi.c
@@ -340,7 +387,9 @@ sysprep/dummy.c
 test-tool/test-tool.c
 utils/boot-analysis/boot-analysis-timeline.c
 utils/boot-analysis/boot-analysis-utils.c
+utils/boot-analysis/boot-analysis-utils.h
 utils/boot-analysis/boot-analysis.c
+utils/boot-analysis/boot-analysis.h
 utils/boot-benchmark/boot-benchmark.c
 utils/qemu-boot/qemu-boot.c
 utils/qemu-speed-test/qemu-speed-test.c
diff --git a/docs/make-internal-documentation.pl b/docs/make-internal-documentation.pl
index 5656b6bb9..b5e5a2c23 100755
--- a/docs/make-internal-documentation.pl
+++ b/docs/make-internal-documentation.pl
@@ -38,21 +38,32 @@ L<guestfs-hacking(1)/INTERNAL DOCUMENTATION>.
 You must specify the name of the output file using the I<-o> or
 I<--output> option, and a list of the C source files in the project.
 
+=head2 Function and struct documentation
+
 Internal documentation is added to the C source files using special
-comments which look like this:
+comments which appear before function or struct definitions:
 
  /**
   * Returns true if C<foo> equals C<bar>.
   */
  bool
  is_equal (const char *foo, const char *bar)
+ {
+   ...
+
+ /**
+  * Struct used to store C<bar>s.
+  */
+ struct foo_bar {
    ...
 
 The comment is written in POD format (see L<perlpod(1)>).  It may be
 on several lines, and be split into paragraphs using blank lines.
 
-The function being documented should appear immediately after the
-special comment, and is also copied into the documentation.
+The thing being documented should appear immediately after the special
+comment, and is also copied into the documentation.
+
+=head2 File documentation
 
 In addition, each C file may have a special comment at the top of the
 file (before any C<#include> lines) which outlines what the file does.
@@ -118,7 +129,7 @@ die "$progname: missing -o/--output parameter\n" unless defined $output;
 die "$progname: missing argument: make-internal-documentation [C source files ...]\n" unless @ARGV >= 1;
 
 # Only consider input files which
-#  - are C source files
+#  - are C source or header files
 #  - exist
 #  - contain /** comments.
 
@@ -126,7 +137,7 @@ my @inputs = ();
 my $input;
 my $path;
 foreach $input (@ARGV) {
-    if ($input =~ /\.c$/) {
+    if ($input =~ /\.[ch]$/) {
         $path = "$srcdir/$input";
         if (-r $path) {
             my @cmd = ("grep", "-q", "^/\\*\\*", $path);
@@ -212,39 +223,62 @@ foreach $dir (@dirs) {
                     print OUTPUT "\n";
                 }
                 else {
-                    # Otherwise it's a function description, so now we
-                    # need to read in the function definition.
-                    my @function = ();
+                    # Otherwise it's a function or struct description,
+                    # so now we need to read in the definition.
+                    my @defn = ();
+                    my $thing = undef;
+                    my $end = undef;
+                    my $name = undef;
                     $found_end = 0;
                     $start_lineno = $lineno;
                     while (<INPUT>) {
                         chomp;
                         $lineno++;
 
-                        if (m/^{/) {
-                            $found_end = 1;
-                            last;
+                        if (defined $end) {
+                            if ($_ eq $end) {
+                                $found_end = 1;
+                                last;
+                            }
+                            else {
+                                push @defn, $_;
+                            }
                         }
                         else {
-                            push @function, $_;
+                            # First line tells us if this is a struct
+                            # or function.
+                            if (/^struct ([\w_]+) \{$/) {
+                                $thing = "Structure";
+                                $name = $1;
+                                $end = "};";
+                            }
+                            else {
+                                $thing = "Function";
+                                $end = "{";
+                            }
+                            push @defn, $_;
                         }
                     }
 
-                    die "$progname: $input: $start_lineno: unterminated function definition"
+                    die "$progname: $input: $start_lineno: unterminated $thing definition"
                         unless $found_end;
 
-                    # Try to determine the name of the function.
-                    my $function;
-                    foreach (@function) {
-                        $function = $1 if /^([\w_]+) \(/;
+                    if ($thing eq "Function") {
+                        # Try to determine the name of the function.
+                        foreach (@defn) {
+                            $name = $1 if /^([\w_]+) \(/;
+                        }
+                        die "$progname: $input: $start_lineno: cannot find the name of this function"
+                            unless defined $name;
                     }
-                    die "$progname: $input: $start_lineno: cannot find the name of this function"
-                        unless defined $function;
 
-                    # Print the function definition, followed by the
-                    # comment.
-                    print OUTPUT "=head4 Function C<$input:$function>\n\n";
-                    print OUTPUT " ", join ("\n ", @function), "\n";
+                    if ($thing eq "Structure") {
+                        push @defn, "};"
+                    }
+
+                    # Print the definition, followed by the comment.
+                    print OUTPUT "=head4 $thing C<$input:$name>\n\n";
+                    print OUTPUT " ", join ("\n ", @defn), "\n";
                     print OUTPUT "\n";
                     print OUTPUT join("\n", @comment), "\n";
                     print OUTPUT "\n";
diff --git a/fish/file-edit.c b/fish/file-edit.c
index d8b7e2a50..e875b5bd2 100644
--- a/fish/file-edit.c
+++ b/fish/file-edit.c
@@ -52,6 +52,20 @@ static char *generate_random_name (const char *filename);
 static char *generate_backup_name (const char *filename,
                                    const char *backup_extension);
 
+/**
+ * Edit C<filename> using the specified C<editor> application.
+ *
+ * If C<backup_extension> is not null, then a copy of C<filename> is
+ * saved with C<backup_extension> appended to its file name.
+ *
+ * If C<editor> is null, then the C<$EDITOR> environment variable will
+ * be queried for the editor application, leaving C<vi> as fallback if
+ * not set.
+ *
+ * Returns C<-1> for failure, C<0> on success, C<1> if the editor did
+ * not change the file (e.g. the user closed the editor without
+ * saving).
+ */
 int
 edit_file_editor (guestfs_h *g, const char *filename, const char *editor,
                   const char *backup_extension, int verbose)
@@ -127,6 +141,14 @@ edit_file_editor (guestfs_h *g, const char *filename, const char *editor,
   return 0;
 }
 
+/**
+ * Edit C<filename> running the specified C<perl_expr> using Perl.
+ *
+ * If C<backup_extension> is not null, then a copy of C<filename> is
+ * saved with C<backup_extension> appended to its file name.
+ *
+ * Returns C<-1> for failure, C<0> on success.
+ */
 int
 edit_file_perl (guestfs_h *g, const char *filename, const char *perl_expr,
                 const char *backup_extension, int verbose)
diff --git a/fish/file-edit.h b/fish/file-edit.h
index cd92e5aa8..a99229b6a 100644
--- a/fish/file-edit.h
+++ b/fish/file-edit.h
@@ -21,28 +21,10 @@
 
 #include <guestfs.h>
 
-/**
- * Edit 'filename' using the specified 'editor' application.
- * If 'backup_extension' is not null, then a copy of 'filename' is saved
- * with 'backup_extension' appended to its file name.
- * If 'editor' is null, then the EDITOR environment variable
- * will be queried for the editor application, leaving "vi" as fallback
- * if not set.
- *
- * Returns -1 for failure, 0 on success, 1 if the editor did not change
- * the file (e.g. the user closed the editor without saving).
- */
 extern int edit_file_editor (guestfs_h *g, const char *filename,
                              const char *editor, const char *backup_extension,
                              int verbose);
 
-/**
- * Edit 'filename' running the specified 'perl_expr' using Perl.
- * If 'backup_extension' is not null, then a copy of 'filename' is saved
- * with 'backup_extension' appended to its file name.
- *
- * Returns -1 for failure, 0 otherwise (on success).
- */
 extern int edit_file_perl (guestfs_h *g, const char *filename,
                            const char *perl_expr,
                            const char *backup_extension, int verbose);
diff --git a/fish/windows.c b/fish/windows.c
index 91eafad8c..3a37be93f 100644
--- a/fish/windows.c
+++ b/fish/windows.c
@@ -41,6 +41,11 @@
 static void mount_drive_letter (guestfs_h *g, char drive_letter,
                                 const char *root, int readonly);
 
+/**
+ * Checks whether C<root> is a Windows installation.
+ *
+ * This relies on an already being done introspection.
+ */
 int
 is_windows (guestfs_h *g, const char *root)
 {
@@ -53,6 +58,33 @@ is_windows (guestfs_h *g, const char *root)
   return w;
 }
 
+/**
+ * Resolves C<path> as possible Windows path according to C<root>,
+ * giving a new path that can be used in libguestfs API calls.
+ *
+ * Notes:
+ *
+ * =over 4
+ *
+ * =item *
+ *
+ * C<root> must be a Windows installation
+ *
+ * =item *
+ *
+ * relies on an already being done introspection
+ *
+ * =item *
+ *
+ * will unmount all the existing mount points and mount the Windows root
+ * (according to C<readonly>)
+ *
+ * =item *
+ *
+ * calls L<exit(3)> on memory allocation failures
+ *
+ * =back
+ */
 char *
 windows_path (guestfs_h *g, const char *root, const char *path, int readonly)
 {
diff --git a/fish/windows.h b/fish/windows.h
index f684784f1..9ffa80264 100644
--- a/fish/windows.h
+++ b/fish/windows.h
@@ -21,24 +21,8 @@
 
 #include <guestfs.h>
 
-/**
- * Checks whether 'root' is a Windows installation.
- *
- * This relies on an already being done introspection.
- */
 extern int is_windows (guestfs_h *g, const char *root);
 
-/**
- * Resolves 'path' as possible Windows path according to 'root',
- * giving a new path that can be used in libguestfs API calls.
- *
- * Notes:
- *  - 'root' must be a Windows installation
- *  - relies on an already being done introspection
- *  - will unmount all the existing mount points and mount the Windows root
- *    (according to 'readonly')
- *  - will exit() on memory allocation failures
- */
 extern char *windows_path (guestfs_h *g, const char *root, const char *path,
                            int readonly);
 
diff --git a/src/guestfs-internal-all.h b/src/guestfs-internal-all.h
index af30e58eb..bae42c221 100644
--- a/src/guestfs-internal-all.h
+++ b/src/guestfs-internal-all.h
@@ -16,8 +16,17 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-/* NB: This contains ONLY definitions which are shared by libguestfs
- * daemon, library, bindings and tools (ie. ALL C code).
+/**
+ * This header contains definitions which are shared by all parts of
+ * libguestfs, ie. the daemon, the library, language bindings and virt
+ * tools (ie. I<all> C code).
+ *
+ * If you need a definition used by only the library, put it in
+ * F<src/guestfs-internal.h> instead.  If you need a definition used
+ * by only the frontend (non-daemon) parts of libguestfs, try
+ * F<src/guestfs-internal-frontend.h>.  If a definition is used by
+ * only a single tool, it should not be in any shared header file at
+ * all.
  */
 
 #ifndef GUESTFS_INTERNAL_ALL_H_
diff --git a/src/guestfs-internal-frontend.h b/src/guestfs-internal-frontend.h
index da7709a7c..bc5750602 100644
--- a/src/guestfs-internal-frontend.h
+++ b/src/guestfs-internal-frontend.h
@@ -16,15 +16,17 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-/* NB: This contains ONLY definitions which are shared by libguestfs
- * library, bindings, tools and tests (NOT the daemon).
+/**
+ * This header file is included in all "frontend" parts of libguestfs,
+ * namely the library, non-C language bindings, virt tools and tests.
  *
- * If a definition is only needed by a single component of libguestfs,
- * then it should NOT be here!
- *
- * The daemon does NOT use this header.  If you need a place to put
+ * The daemon does B<not> use this header.  If you need a place to put
  * something shared with absolutely everything including the daemon,
- * put it in 'src/guestfs-internal-all.h'.
+ * put it in F<src/guestfs-internal-all.h>
+ *
+ * If a definition is only needed by a single component of libguestfs
+ * (eg. just the library, or just a single virt tool) then it should
+ * B<not> be here!
  */
 
 #ifndef GUESTFS_INTERNAL_FRONTEND_H_
diff --git a/src/guestfs-internal.h b/src/guestfs-internal.h
index d437b9a18..092c6d579 100644
--- a/src/guestfs-internal.h
+++ b/src/guestfs-internal.h
@@ -16,6 +16,14 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/**
+ * This header file is included in the libguestfs library (F<src/>)
+ * only.
+ *
+ * See also F<src/guestfs-internal-frontend.h> and
+ * F<src/guestfs-internal-all.h>
+ */
+
 #ifndef GUESTFS_INTERNAL_H_
 #define GUESTFS_INTERNAL_H_
 
diff --git a/src/private-data.c b/src/private-data.c
index 3f6e6f11f..64fe9ef87 100644
--- a/src/private-data.c
+++ b/src/private-data.c
@@ -16,6 +16,17 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/**
+ * Implement a private data area where libguestfs C API users can
+ * attach arbitrary pieces of data to a C<guestfs_h> handle.
+ *
+ * For more information see L<guestfs(3)/PRIVATE DATA AREA>.
+ *
+ * Language bindings do not generally expose this, largely because in
+ * non-C languages it is easy to associate data with handles in other
+ * ways (using hash tables or maps).
+ */
+
 #include <config.h>
 
 #include <stdio.h>
@@ -29,9 +40,13 @@
 #include "guestfs.h"
 #include "guestfs-internal.h"
 
-/* Note the private data area is allocated lazily, since the vast
- * majority of callers will never use it.  This means g->pda is
- * likely to be NULL.
+/**
+ * The private data area is internally stored as a gnulib hash
+ * table containing C<pda_entry> structures.
+ *
+ * Note the private data area is allocated lazily, since the vast
+ * majority of callers will never use it.  This means C<g-E<gt>pda> is
+ * likely to be C<NULL>.
  */
 struct pda_entry {
   char *key;                    /* key */