availability: Add optional groups and implement guestfs_available call.

The current groups are defined very conservatively using the
following criteria:
 (a) Would be impossible to implement on Windows because of
     sheer architectural differences (eg: mknod).
 (b) Already optional (augeas, inotify).
 (c) Not currently optional but not implemented on older RHEL and
     Debian releases (ntfs-3g.probe, scrub, zerofree).

The optional groups I've defined according to these criteria are:

 . augeas
 . inotify
 . linuxfsuuid
 . linuxmodules
 . linuxxattrs
 . lvm2
 . mknod
 . ntfs3g
 . scrub
 . selinux
 . zerofree

(Note that these choices don't prevent us from adding more
optional groups in future.  On the other hand to avoid breaking
ABIs we would not wish to change the above groups).

The rest of this large commit is really just implementation:

Each optional function is classified using Optional "group"
flag in the generator.

The daemon has to implement a function

  int optgroup_<name>_available (void);

for each optional group.  Some of these functions are fixed at
compile time, and some do simple run-time tests.

The do_available implementation in the daemon looks up the correct
function in a table and runs it.

We document the optional groups in the guestfs(3) man page.

Also: I added a NOT_AVAILABLE macro in order to unify all the
existing places where we had a message equivalent to
"function __func__ is not available".

20 files changed, 388 insertions, 151 deletions

diff --git a/.gitignore b/.gitignore
index b3869c52..3348b979 100644
--- a/.gitignore
+++ b/.gitignore
@@ -48,6 +48,8 @@ daemon/guestfsd
 daemon/install-sh
 daemon/missing
 daemon/names.c
+daemon/optgroups.c
+daemon/optgroups.h
 daemon/stubs.c
 depcomp
 .deps
@@ -65,6 +67,7 @@ guestfish.1
 guestfish-actions.pod
 guestfs.3
 guestfs-actions.pod
+guestfs-availability.pod
 guestfs-structs.pod
 haskell/Bindtests
 haskell/Bindtests.hs
diff --git a/Makefile.am b/Makefile.am
index 9332a10d..bbdb0ed4 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -57,8 +57,9 @@ SUBDIRS += haskell
 endif
 
 generator_built = \
-	guestfs-structs.pod \
 	guestfs-actions.pod \
+	guestfs-availability.pod \
+	guestfs-structs.pod \
 	guestfish-actions.pod
 
 EXTRA_DIST = \
@@ -83,15 +84,23 @@ EXTRA_DIST = \
 	libguestfs.3
 
 # Manual pages.
-# guestfs-actions.pod and guestfs-structs are autogenerated.  There is
-# no include mechanism for POD, so we have to do it by hand.
+# guestfs-actions.pod, guestfs-availability.pod and guestfs-structs
+# are autogenerated.  There is no include mechanism for POD, so we
+# have to do it by hand.
 
 man_MANS = guestfs.3 libguestfs.3 guestfish.1
 
-guestfs.3: guestfs.pod guestfs-actions.pod guestfs-structs.pod
+guestfs.3: guestfs.pod \
+		guestfs-actions.pod \
+		guestfs-availability.pod \
+		guestfs-structs.pod
 	sed \
-	  -e '/@ACTIONS@/rguestfs-actions.pod' -e 's/@ACTIONS@//' \
-	  -e '/@STRUCTS@/rguestfs-structs.pod' -e 's/@STRUCTS@//' \
+	  -e '/@ACTIONS@/rguestfs-actions.pod' \
+	  -e 's/@ACTIONS@//' \
+	  -e '/@AVAILABILITY@/rguestfs-availability.pod' \
+	  -e 's/@AVAILABILITY@//' \
+	  -e '/@STRUCTS@/rguestfs-structs.pod' \
+	  -e 's/@STRUCTS@//' \
 	  < $< | \
 	$(POD2MAN) \
 	  --section 3 \
@@ -113,11 +122,18 @@ guestfish.1: guestfish.pod guestfish-actions.pod
 
 noinst_DATA = html/guestfs.3.html html/guestfish.1.html
 
-html/guestfs.3.html: guestfs.pod guestfs-actions.pod guestfs-structs.pod
+html/guestfs.3.html: guestfs.pod \
+		guestfs-actions.pod \
+		guestfs-availability.pod \
+		guestfs-structs.pod
 	mkdir -p html
 	sed \
-	  -e '/@ACTIONS@/rguestfs-actions.pod' -e 's/@ACTIONS@//' \
-	  -e '/@STRUCTS@/rguestfs-structs.pod' -e 's/@STRUCTS@//' \
+	  -e '/@ACTIONS@/rguestfs-actions.pod' \
+	  -e 's/@ACTIONS@//' \
+	  -e '/@AVAILABILITY@/rguestfs-availability.pod' \
+	  -e 's/@AVAILABILITY@//' \
+	  -e '/@STRUCTS@/rguestfs-structs.pod' \
+	  -e 's/@STRUCTS@//' \
 	  < $< | \
 	pod2html \
 	  --css 'pod.css' \
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index d851e527..9fa8ddab 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -81,6 +81,8 @@ guestfsd_SOURCES = \
 	mount.c \
 	names.c \
 	ntfs.c \
+	optgroups.c \
+	optgroups.h \
 	parted.c \
 	pingdaemon.c \
 	proto.c \
diff --git a/daemon/augeas.c b/daemon/augeas.c
index b56012cd..be53d294 100644
--- a/daemon/augeas.c
+++ b/daemon/augeas.c
@@ -29,6 +29,7 @@
 
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
 
 #ifdef HAVE_AUGEAS
 /* The Augeas handle.  We maintain a single handle per daemon, which
@@ -45,6 +46,18 @@ static augeas *aug = NULL;
     }									\
   }									\
   while (0)
+
+int
+optgroup_augeas_available (void)
+{
+  return 1;
+}
+#else /* !HAVE_AUGEAS */
+int
+optgroup_augeas_available (void)
+{
+  return 0;
+}
 #endif
 
 /* We need to rewrite the root path so it is based at /sysroot. */
@@ -75,8 +88,7 @@ do_aug_init (const char *root, int flags)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -91,8 +103,7 @@ do_aug_close (void)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -111,8 +122,7 @@ do_aug_defvar (const char *name, const char *expr)
   }
   return r;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -133,8 +143,7 @@ do_aug_defnode (const char *name, const char *expr, const char *val)
   r.b = created;
   return &r;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -176,8 +185,7 @@ do_aug_get (const char *path)
 
   return v;			/* Caller frees. */
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (NULL);
 #endif
 }
 
@@ -197,8 +205,7 @@ do_aug_set (const char *path, const char *val)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -218,8 +225,7 @@ do_aug_insert (const char *path, const char *label, int before)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -239,8 +245,7 @@ do_aug_rm (const char *path)
 
   return r;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -260,8 +265,7 @@ do_aug_mv (const char *src, const char *dest)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -295,8 +299,7 @@ do_aug_match (const char *path)
 
   return matches;		/* Caller frees. */
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (NULL);
 #endif
 }
 
@@ -313,8 +316,7 @@ do_aug_save (void)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -331,8 +333,7 @@ do_aug_load (void)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -379,7 +380,6 @@ do_aug_ls (const char *path)
   sort_strings (matches, count_strings ((void *) matches));
   return matches;		/* Caller frees. */
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (NULL);
 #endif
 }
diff --git a/daemon/available.c b/daemon/available.c
index b43d1820..77fdfa2c 100644
--- a/daemon/available.c
+++ b/daemon/available.c
@@ -29,9 +29,26 @@
 int
 do_available (char *const *groups)
 {
-  if (groups[0] != NULL) {
-    reply_with_error ("%s: unknown group", groups[0]);
-    return -1;
+  int av;
+  size_t i, j;
+
+  for (i = 0; groups[i] != NULL; ++i) {
+    for (j = 0; optgroups[j].group != NULL; ++j) {
+      if (STREQ (groups[i], optgroups[j].group)) {
+        av = optgroups[j].available ();
+        if (!av) {
+          reply_with_error ("%s: group not available", optgroups[j].group);
+          return -1;
+        }
+        break; /* out of for (j) loop */
+      }
+    }
+
+    /* Unknown group? */
+    if (optgroups[j].group == NULL) {
+      reply_with_error ("%s: unknown group", groups[i]);
+      return -1;
+    }
   }
 
   return 0;
diff --git a/daemon/configure.ac b/daemon/configure.ac
index a1f54a3b..c6d9d98f 100644
--- a/daemon/configure.ac
+++ b/daemon/configure.ac
@@ -133,7 +133,7 @@ AC_STRUCT_DIRENT_D_TYPE
 dnl Check if stat has the required fields.
 AC_STRUCT_ST_BLOCKS
 AC_CHECK_MEMBER([struct stat.st_blksize],[
-	AC_DEFINE([HAVE_STRUCT_STAT_ST_BLKSIZE],[1],[Define to 1 if 'st_blksize' is a member of 'struct stat'])])
+        AC_DEFINE([HAVE_STRUCT_STAT_ST_BLKSIZE],[1],[Define to 1 if 'st_blksize' is a member of 'struct stat'])])
 
 dnl Check for Augeas (now optional).
 AC_CHECK_LIB([augeas],[aug_match],[
@@ -164,17 +164,17 @@ AC_CHECK_LIB([portablexdr],[xdrmem_create],[],[
 
 dnl Functions which may not be available in older distributions.
 AC_CHECK_FUNCS([\
-	futimens \
-	getxattr \
-	inotify_init1 \
-	lgetxattr \
-	listxattr \
-	llistxattr \
-	lsetxattr \
-	lremovexattr \
-	mknod \
-	removexattr \
-	setxattr])
+        futimens \
+        getxattr \
+        inotify_init1 \
+        lgetxattr \
+        listxattr \
+        llistxattr \
+        lsetxattr \
+        lremovexattr \
+        mknod \
+        removexattr \
+        setxattr])
 
 dnl Headers.
 AC_CHECK_HEADERS([\
diff --git a/daemon/daemon.h b/daemon/daemon.h
index 120c86cc..7ba75990 100644
--- a/daemon/daemon.h
+++ b/daemon/daemon.h
@@ -105,6 +105,13 @@ extern guestfs_int_lvm_lv_list *parse_command_line_lvs (void);
 /*-- in proto.c --*/
 extern void main_loop (int sock) __attribute__((noreturn));
 
+/*-- in optgroups.c (auto-generated) --*/
+struct optgroup {
+  const char *group;            /* Name of the optional group. */
+  int (*available) (void);      /* Function to test availability. */
+};
+extern struct optgroup optgroups[];
+
 /* ordinary daemon functions use these to indicate errors */
 extern void reply_with_error (const char *fs, ...)
   __attribute__((format (printf,1,2)));
@@ -225,6 +232,16 @@ extern void reply (xdrproc_t xdrp, char *ret);
   }									\
   while (0)
 
+/* Marks functions which are not available.
+ * NB. Cannot be used for FileIn functions.
+ */
+#define NOT_AVAILABLE(errcode)                                          \
+  do {									\
+    reply_with_error ("%s: function not available", __func__);          \
+    return (errcode);							\
+  }									\
+  while (0)
+
 #ifndef __attribute__
 # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8)
 #  define __attribute__(x) /* empty */
diff --git a/daemon/inotify.c b/daemon/inotify.c
index 465d0b6e..24ce76e2 100644
--- a/daemon/inotify.c
+++ b/daemon/inotify.c
@@ -31,6 +31,7 @@
 #include "../src/guestfs_protocol.h"
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
 
 #ifdef HAVE_SYS_INOTIFY_H
 /* Currently open inotify handle, or -1 if not opened. */
@@ -38,6 +39,18 @@ static int inotify_fd = -1;
 
 static char inotify_buf[64*1024*1024];	/* Event buffer, [0..posn-1] is valid */
 static size_t inotify_posn = 0;
+
+int
+optgroup_inotify_available (void)
+{
+  return 1;
+}
+#else /* !HAVE_SYS_INOTIFY_H */
+int
+optgroup_inotify_available (void)
+{
+  return 0;
+}
 #endif
 
 /* Because inotify_init does NEED_ROOT, NEED_INOTIFY implies NEED_ROOT. */
@@ -106,8 +119,7 @@ do_inotify_init (int max_events)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -132,8 +144,7 @@ do_inotify_close (void)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -161,8 +172,7 @@ do_inotify_add_watch (const char *path, int mask)
 
   return r;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -179,8 +189,7 @@ do_inotify_rm_watch (int wd)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -294,8 +303,7 @@ do_inotify_read (void)
   free (ret);
   return NULL;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (NULL);
 #endif
 }
 
@@ -371,7 +379,6 @@ do_inotify_files (void)
   unlink ("/tmp/inotify");
   return NULL;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (NULL);
 #endif
 }
diff --git a/daemon/lvm.c b/daemon/lvm.c
index 3920e95b..564517c5 100644
--- a/daemon/lvm.c
+++ b/daemon/lvm.c
@@ -26,6 +26,14 @@
 #include "daemon.h"
 #include "c-ctype.h"
 #include "actions.h"
+#include "optgroups.h"
+
+int
+optgroup_lvm2_available (void)
+{
+  int r = access ("/sbin/lvm", X_OK);
+  return r == 0;
+}
 
 /* LVM actions.  Keep an eye on liblvm, although at the time
  * of writing it hasn't progressed very far.
diff --git a/daemon/mknod.c b/daemon/mknod.c
index 6ff88efa..46a18392 100644
--- a/daemon/mknod.c
+++ b/daemon/mknod.c
@@ -29,6 +29,21 @@
 #include "../src/guestfs_protocol.h"
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+#ifdef HAVE_MKNOD
+int
+optgroup_mknod_available (void)
+{
+  return 1;
+}
+#else
+int
+optgroup_mknod_available (void)
+{
+  return 0;
+}
+#endif
 
 int
 do_mknod (int mode, int devmajor, int devminor, const char *path)
@@ -47,8 +62,7 @@ do_mknod (int mode, int devmajor, int devminor, const char *path)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
diff --git a/daemon/modprobe.c b/daemon/modprobe.c
index 7e3d1b70..ac62b349 100644
--- a/daemon/modprobe.c
+++ b/daemon/modprobe.c
@@ -23,6 +23,14 @@
 
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+int
+optgroup_linuxmodules_available (void)
+{
+  int r = access ("/sbin/modprobe", X_OK);
+  return r == 0;
+}
 
 int
 do_modprobe (const char *module)
diff --git a/daemon/ntfs.c b/daemon/ntfs.c
index 85deb654..b3530084 100644
--- a/daemon/ntfs.c
+++ b/daemon/ntfs.c
@@ -25,6 +25,14 @@
 
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+int
+optgroup_ntfs3g_available (void)
+{
+  int r = access ("/bin/ntfs-3g.probe", X_OK);
+  return r == 0;
+}
 
 int
 do_ntfs_3g_probe (int rw, const char *device)
diff --git a/daemon/scrub.c b/daemon/scrub.c
index 15c8b6c2..e37a1e11 100644
--- a/daemon/scrub.c
+++ b/daemon/scrub.c
@@ -26,6 +26,14 @@
 
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+int
+optgroup_scrub_available (void)
+{
+  int r = access ("/usr/bin/scrub", X_OK);
+  return r == 0;
+}
 
 int
 do_scrub_device (const char *device)
diff --git a/daemon/selinux.c b/daemon/selinux.c
index 3b4b9ba6..e49e657b 100644
--- a/daemon/selinux.c
+++ b/daemon/selinux.c
@@ -29,6 +29,21 @@
 #include "../src/guestfs_protocol.h"
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+#if defined(HAVE_LIBSELINUX)
+int
+optgroup_selinux_available (void)
+{
+  return 1;
+}
+#else /* !HAVE_LIBSELINUX */
+int
+optgroup_selinux_available (void)
+{
+  return 0;
+}
+#endif /* !HAVE_LIBSELINUX */
 
 /* setcon is only valid under the following circumstances:
  * - single threaded
@@ -45,8 +60,7 @@ do_setcon (const char *context)
 
   return 0;
 #else
-  reply_with_error ("%s is not available", __func__);
-  return -1;
+  NOT_AVAILABLE (-1);
 #endif
 }
 
@@ -71,7 +85,6 @@ do_getcon (void)
 
   return r;                     /* caller frees */
 #else
-  reply_with_error ("%s is not available", __func__);
-  return NULL;
+  NOT_AVAILABLE (NULL);
 #endif
 }
diff --git a/daemon/swap.c b/daemon/swap.c
index bcc5f1b1..2d3d9ff4 100644
--- a/daemon/swap.c
+++ b/daemon/swap.c
@@ -26,6 +26,25 @@
 #include "../src/guestfs_protocol.h"
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+/* Convenient place to test for the later version of e2fsprogs
+ * and util-linux which supports -U parameters to specify UUIDs.
+ * (Not supported in RHEL 5).
+ */
+int
+optgroup_linuxfsuuid_available (void)
+{
+  char *err;
+  int av;
+
+  /* Ignore return code - mkswap --help *will* fail. */
+  command (NULL, &err, "/sbin/mkswap", "--help", NULL);
+
+  av = strstr (err, "-U") != NULL;
+  free (err);
+  return av;
+}
 
 static int
 mkswap (const char *device, const char *flag, const char *value)
diff --git a/daemon/xattr.c b/daemon/xattr.c
index c218dea1..e58dc7ea 100644
--- a/daemon/xattr.c
+++ b/daemon/xattr.c
@@ -24,16 +24,23 @@
 #include "../src/guestfs_protocol.h"
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
 
 #if defined(HAVE_ATTR_XATTR_H) || defined(HAVE_SYS_XATTR_H)
 
-#ifdef HAVE_ATTR_XATTR_H
-#include <attr/xattr.h>
-#else
-#ifdef HAVE_SYS_XATTR_H
-#include <sys/xattr.h>
-#endif
-#endif
+# ifdef HAVE_ATTR_XATTR_H
+#  include <attr/xattr.h>
+# else
+#  ifdef HAVE_SYS_XATTR_H
+#   include <sys/xattr.h>
+#  endif
+# endif
+
+int
+optgroup_linuxxattrs_available (void)
+{
+  return 1;
+}
 
 static guestfs_int_xattr_list *getxattrs (const char *path, ssize_t (*listxattr) (const char *path, char *list, size_t size), ssize_t (*getxattr) (const char *path, const char *name, void *value, size_t size));
 static int _setxattr (const char *xattr, const char *val, int vallen, const char *path, int (*setxattr) (const char *path, const char *name, const void *value, size_t size, int flags));
@@ -442,54 +449,52 @@ do_lxattrlist (const char *path, char *const *names)
 }
 
 #else /* no xattr.h */
+int
+optgroup_linuxxattrs_available (void)
+{
+  return 0;
+}
 
 guestfs_int_xattr_list *
 do_getxattrs (const char *path)
 {
-  reply_with_error ("getxattrs: no support for xattrs");
-  return NULL;
+  NOT_AVAILABLE (NULL);
 }
 
 guestfs_int_xattr_list *
 do_lgetxattrs (const char *path)
 {
-  reply_with_error ("lgetxattrs: no support for xattrs");
-  return NULL;
+  NOT_AVAILABLE (NULL);
 }
 
 int
 do_setxattr (const char *xattr, const char *val, int vallen, const char *path)
 {
-  reply_with_error ("setxattr: no support for xattrs");
-  return -1;
+  NOT_AVAILABLE (-1);
 }
 
 int
 do_lsetxattr (const char *xattr, const char *val, int vallen, const char *path)
 {
-  reply_with_error ("lsetxattr: no support for xattrs");
-  return -1;
+  NOT_AVAILABLE (-1);
 }
 
 int
 do_removexattr (const char *xattr, const char *path)
 {
-  reply_with_error ("removexattr: no support for xattrs");
-  return -1;
+  NOT_AVAILABLE (-1);
 }
 
 int
 do_lremovexattr (const char *xattr, const char *path)
 {
-  reply_with_error ("lremovexattr: no support for xattrs");
-  return -1;
+  NOT_AVAILABLE (-1);
 }
 
 guestfs_int_xattr_list *
 do_lxattrlist (const char *path, char *const *names)
 {
-  reply_with_error ("lxattrlist: no support for xattrs");
-  return NULL;
+  NOT_AVAILABLE (NULL);
 }
 
 #endif /* no xattr.h */
diff --git a/daemon/zerofree.c b/daemon/zerofree.c
index ffb9b70b..05a547bd 100644
--- a/daemon/zerofree.c
+++ b/daemon/zerofree.c
@@ -26,6 +26,14 @@
 
 #include "daemon.h"
 #include "actions.h"
+#include "optgroups.h"
+
+int
+optgroup_zerofree_available (void)
+{
+  int r = access ("/usr/sbin/zerofree", X_OK);
+  return r == 0;
+}
 
 int
 do_zerofree (const char *device)
diff --git a/guestfs.pod b/guestfs.pod
index 0e7079c2..4a477330 100644
--- a/guestfs.pod
+++ b/guestfs.pod
@@ -623,6 +623,13 @@ developer to program in confidence against libguestfs.
 
 @STRUCTS@
 
+=head1 AVAILABILITY
+
+Using L</guestfs_available> you can test availability of
+the following groups of functions:
+
+@AVAILABILITY@
+
 =head1 STATE MACHINE AND LOW-LEVEL EVENT API
 
 Internally, libguestfs is implemented by running a virtual machine
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 2c7998d7..7707811f 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -37,6 +37,7 @@ daemon/modprobe.c
 daemon/mount.c
 daemon/names.c
 daemon/ntfs.c
+daemon/optgroups.c
 daemon/parted.c
 daemon/pingdaemon.c
 daemon/proto.c
diff --git a/src/generator.ml b/src/generator.ml
index cceb1915..08817c12 100755
--- a/src/generator.ml
+++ b/src/generator.ml
@@ -175,6 +175,7 @@ type flags =
   | NotInFish		  (* do not export via guestfish *)
   | NotInDocs		  (* do not add this function to documentation *)
   | DeprecatedBy of string (* function is deprecated, use .. instead *)
+  | Optional of string	  (* function is part of an optional group *)
 
 (* You can supply zero or as many tests as you want per API call.
  *
@@ -979,7 +980,7 @@ The full partition device names are returned, eg. C</dev/sda1>
 This does not return logical volumes.  For that you will need to
 call C<guestfs_lvs>.");
 
-  ("pvs", (RStringList "physvols", []), 9, [],
+  ("pvs", (RStringList "physvols", []), 9, [Optional "lvm2"],
    [InitBasicFSonLVM, Always, TestOutputListOfDevices (
       [["pvs"]], ["/dev/sda1"]);
     InitEmpty, Always, TestOutputListOfDevices (
@@ -998,7 +999,7 @@ PVs (eg. C</dev/sda2>).
 
 See also C<guestfs_pvs_full>.");
 
-  ("vgs", (RStringList "volgroups", []), 10, [],
+  ("vgs", (RStringList "volgroups", []), 10, [Optional "lvm2"],
    [InitBasicFSonLVM, Always, TestOutputList (
       [["vgs"]], ["VG"]);
     InitEmpty, Always, TestOutputList (
@@ -1019,7 +1020,7 @@ detected (eg. C<VolGroup00>).
 
 See also C<guestfs_vgs_full>.");
 
-  ("lvs", (RStringList "logvols", []), 11, [],
+  ("lvs", (RStringList "logvols", []), 11, [Optional "lvm2"],
    [InitBasicFSonLVM, Always, TestOutputList (
       [["lvs"]], ["/dev/VG/LV"]);
     InitEmpty, Always, TestOutputList (
@@ -1043,21 +1044,21 @@ This returns a list of the logical volume device names
 
 See also C<guestfs_lvs_full>.");
 
-  ("pvs_full", (RStructList ("physvols", "lvm_pv"), []), 12, [],
+  ("pvs_full", (RStructList ("physvols", "lvm_pv"), []), 12, [Optional "lvm2"],
    [], (* XXX how to test? *)
    "list the LVM physical volumes (PVs)",
    "\
 List all the physical volumes detected.  This is the equivalent
 of the L<pvs(8)> command.  The \"full\" version includes all fields.");
 
-  ("vgs_full", (RStructList ("volgroups", "lvm_vg"), []), 13, [],
+  ("vgs_full", (RStructList ("volgroups", "lvm_vg"), []), 13, [Optional "lvm2"],
    [], (* XXX how to test? *)
    "list the LVM volume groups (VGs)",
    "\
 List all the volumes groups detected.  This is the equivalent
 of the L<vgs(8)> command.  The \"full\" version includes all fields.");
 
-  ("lvs_full", (RStructList ("logvols", "lvm_lv"), []), 14, [],
+  ("lvs_full", (RStructList ("logvols", "lvm_lv"), []), 14, [Optional "lvm2"],
    [], (* XXX how to test? *)
    "list the LVM logical volumes (LVs)",
    "\
@@ -1081,7 +1082,7 @@ Note that this function cannot correctly handle binary files
 as end of line).  For those you need to use the C<guestfs_read_file>
 function which has a more complex interface.");
 
-  ("aug_init", (RErr, [Pathname "root"; Int "flags"]), 16, [],
+  ("aug_init", (RErr, [Pathname "root"; Int "flags"]), 16, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "create a new Augeas handle",
    "\
@@ -1132,7 +1133,7 @@ To close the handle, you can call C<guestfs_aug_close>.
 
 To find out more about Augeas, see L<http://augeas.net/>.");
 
-  ("aug_close", (RErr, []), 26, [],
+  ("aug_close", (RErr, []), 26, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "close the current Augeas handle",
    "\
@@ -1141,7 +1142,7 @@ used by it.  After calling this, you have to call
 C<guestfs_aug_init> again before you can use any other
 Augeas functions.");
 
-  ("aug_defvar", (RInt "nrnodes", [String "name"; OptString "expr"]), 17, [],
+  ("aug_defvar", (RInt "nrnodes", [String "name"; OptString "expr"]), 17, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "define an Augeas variable",
    "\
@@ -1152,7 +1153,7 @@ undefined.
 On success this returns the number of nodes in C<expr>, or
 C<0> if C<expr> evaluates to something which is not a nodeset.");
 
-  ("aug_defnode", (RStruct ("nrnodescreated", "int_bool"), [String "name"; String "expr"; String "val"]), 18, [],
+  ("aug_defnode", (RStruct ("nrnodescreated", "int_bool"), [String "name"; String "expr"; String "val"]), 18, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "define an Augeas node",
    "\
@@ -1167,20 +1168,20 @@ On success this returns a pair containing the
 number of nodes in the nodeset, and a boolean flag
 if a node was created.");
 
-  ("aug_get", (RString "val", [String "augpath"]), 19, [],
+  ("aug_get", (RString "val", [String "augpath"]), 19, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "look up the value of an Augeas path",
    "\
 Look up the value associated with C<path>.  If C<path>
 matches exactly one node, the C<value> is returned.");
 
-  ("aug_set", (RErr, [String "augpath"; String "val"]), 20, [],
+  ("aug_set", (RErr, [String "augpath"; String "val"]), 20, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "set Augeas path to value",
    "\
 Set the value associated with C<path> to C<value>.");
 
-  ("aug_insert", (RErr, [String "augpath"; String "label"; Bool "before"]), 21, [],
+  ("aug_insert", (RErr, [String "augpath"; String "label"; Bool "before"]), 21, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "insert a sibling Augeas node",
    "\
@@ -1192,7 +1193,7 @@ C<path> must match exactly one existing node in the tree, and
 C<label> must be a label, ie. not contain C</>, C<*> or end
 with a bracketed index C<[N]>.");
 
-  ("aug_rm", (RInt "nrnodes", [String "augpath"]), 22, [],
+  ("aug_rm", (RInt "nrnodes", [String "augpath"]), 22, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "remove an Augeas path",
    "\
@@ -1200,14 +1201,14 @@ Remove C<path> and all of its children.
 
 On success this returns the number of entries which were removed.");
 
-  ("aug_mv", (RErr, [String "src"; String "dest"]), 23, [],
+  ("aug_mv", (RErr, [String "src"; String "dest"]), 23, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "move Augeas node",
    "\
 Move the node C<src> to C<dest>.  C<src> must match exactly
 one node.  C<dest> is overwritten if it exists.");
 
-  ("aug_match", (RStringList "matches", [String "augpath"]), 24, [],
+  ("aug_match", (RStringList "matches", [String "augpath"]), 24, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "return Augeas nodes which match augpath",
    "\
@@ -1215,7 +1216,7 @@ Returns a list of paths which match the path expression C<path>.
 The returned paths are sufficiently qualified so that they match
 exactly one node in the current tree.");
 
-  ("aug_save", (RErr, []), 25, [],
+  ("aug_save", (RErr, []), 25, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "write all pending Augeas changes to disk",
    "\
@@ -1224,7 +1225,7 @@ This writes all pending changes to disk.
 The flags which were passed to C<guestfs_aug_init> affect exactly
 how files are saved.");
 
-  ("aug_load", (RErr, []), 27, [],
+  ("aug_load", (RErr, []), 27, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "load files into the tree",
    "\
@@ -1233,7 +1234,7 @@ Load files into the tree.
 See C<aug_load> in the Augeas documentation for the full gory
 details.");
 
-  ("aug_ls", (RStringList "matches", [String "augpath"]), 28, [],
+  ("aug_ls", (RStringList "matches", [String "augpath"]), 28, [Optional "augeas"],
    [], (* XXX Augeas code needs tests. *)
    "list Augeas nodes under augpath",
    "\
@@ -1366,7 +1367,7 @@ other objects like files.
 
 See also C<guestfs_stat>.");
 
-  ("pvcreate", (RErr, [Device "device"]), 39, [],
+  ("pvcreate", (RErr, [Device "device"]), 39, [Optional "lvm2"],
    [InitEmpty, Always, TestOutputListOfDevices (
       [["sfdiskM"; "/dev/sda"; ",100 ,200 ,"];
        ["pvcreate"; "/dev/sda1"];
@@ -1379,7 +1380,7 @@ This creates an LVM physical volume on the named C<device>,
 where C<device> should usually be a partition name such
 as C</dev/sda1>.");
 
-  ("vgcreate", (RErr, [String "volgroup"; DeviceList "physvols"]), 40, [],
+  ("vgcreate", (RErr, [String "volgroup"; DeviceList "physvols"]), 40, [Optional "lvm2"],
    [InitEmpty, Always, TestOutputList (
       [["sfdiskM"; "/dev/sda"; ",100 ,200 ,"];
        ["pvcreate"; "/dev/sda1"];
@@ -1393,7 +1394,7 @@ as C</dev/sda1>.");
 This creates an LVM volume group called C<volgroup>
 from the non-empty list of physical volumes C<physvols>.");
 
-  ("lvcreate", (RErr, [String "logvol"; String "volgroup"; Int "mbytes"]), 41, [],
+  ("lvcreate", (RErr, [String "logvol"; String "volgroup"; Int "mbytes"]), 41, [Optional "lvm2"],
    [InitEmpty, Always, TestOutputList (
       [["sfdiskM"; "/dev/sda"; ",100 ,200 ,"];
        ["pvcreate"; "/dev/sda1"];
@@ -1544,7 +1545,7 @@ This unmounts all mounted filesystems.
 
 Some internal mounts are not unmounted by this call.");
 
-  ("lvm_remove_all", (RErr, []), 48, [DangerWillRobinson],
+  ("lvm_remove_all", (RErr, []), 48, [DangerWillRobinson; Optional "lvm2"],
    [],
    "remove all LVM LVs, VGs and PVs",
    "\
@@ -2035,7 +2036,7 @@ There is no comprehensive help for this command.  You have
 to look at the file C<daemon/debug.c> in the libguestfs source
 to find out what you can do.");
 
-  ("lvremove", (RErr, [Device "device"]), 77, [],
+  ("lvremove", (RErr, [Device "device"]), 77, [Optional "lvm2"],
    [InitEmpty, Always, TestOutputList (
       [["part_disk"; "/dev/sda"; "mbr"];
        ["pvcreate"; "/dev/sda1"];
@@ -2068,7 +2069,7 @@ the path to the LV, such as C</dev/VG/LV>.
 You can also remove all LVs in a volume group by specifying
 the VG name, C</dev/VG>.");
 
-  ("vgremove", (RErr, [String "vgname"]), 78, [],
+  ("vgremove", (RErr, [String "vgname"]), 78, [Optional "lvm2"],
    [InitEmpty, Always, TestOutputList (
       [["part_disk"; "/dev/sda"; "mbr"];
        ["pvcreate"; "/dev/sda1"];
@@ -2092,7 +2093,7 @@ Remove an LVM volume group C<vgname>, (for example C<VG>).
 This also forcibly removes all logical volumes in the volume
 group (if any).");
 
-  ("pvremove", (RErr, [Device "device"]), 79, [],
+  ("pvremove", (RErr, [Device "device"]), 79, [Optional "lvm2"],
    [InitEmpty, Always, TestOutputListOfDevices (
       [["part_disk"; "/dev/sda"; "mbr"];
        ["pvcreate"; "/dev/sda1"];
@@ -2387,7 +2388,7 @@ The returned strings are transcoded to UTF-8.");
 This runs C<hexdump -C> on the given C<path>.  The result is
 the human-readable, canonical hex dump of the file.");
 
-  ("zerofree", (RErr, [Device "device"]), 97, [],
+  ("zerofree", (RErr, [Device "device"]), 97, [Optional "zerofree"],
    [InitNone, Always, TestOutput (
       [["part_disk"; "/dev/sda"; "mbr"];
        ["mkfs"; "ext3"; "/dev/sda1"];
@@ -2410,7 +2411,7 @@ mounted.
 It is possible that using this program can damage the filesystem
 or data on the filesystem.");
 
-  ("pvresize", (RErr, [Device "device"]), 98, [],
+  ("pvresize", (RErr, [Device "device"]), 98, [Optional "lvm2"],
    [],
    "resize an LVM physical volume",
    "\
@@ -2462,7 +2463,7 @@ kernel's idea of the geometry (see C<guestfs_sfdisk_kernel_geometry>).
 The result is in human-readable format, and not designed to
 be parsed.");
 
-  ("vg_activate_all", (RErr, [Bool "activate"]), 103, [],
+  ("vg_activate_all", (RErr, [Bool "activate"]), 103, [Optional "lvm2"],
    [],
    "activate or deactivate all volume groups",
    "\
@@ -2474,7 +2475,7 @@ then those devices disappear.
 
 This command is the same as running C<vgchange -a y|n>");
 
-  ("vg_activate", (RErr, [Bool "activate"; StringList "volgroups"]), 104, [],
+  ("vg_activate", (RErr, [Bool "activate"; StringList "volgroups"]), 104, [Optional "lvm2"],
    [],
    "activate or deactivate some volume groups",
    "\
@@ -2489,7 +2490,7 @@ This command is the same as running C<vgchange -a y|n volgroups...>
 Note that if C<volgroups> is an empty list then B<all> volume groups
 are activated or deactivated.");
 
-  ("lvresize", (RErr, [Device "device"; Int "mbytes"]), 105, [],
+  ("lvresize", (RErr, [Device "device"; Int "mbytes"]), 105, [Optional "lvm2"],
    [InitNone, Always, TestOutput (
       [["part_disk"; "/dev/sda"; "mbr"];
        ["pvcreate"; "/dev/sda1"];
@@ -2582,7 +2583,7 @@ This command is only needed because of C<guestfs_resize2fs>
    "\
 Sleep for C<secs> seconds.");
 
-  ("ntfs_3g_probe", (RInt "status", [Bool "rw"; Device "device"]), 110, [],
+  ("ntfs_3g_probe", (RInt "status", [Bool "rw"; Device "device"]), 110, [Optional "ntfs3g"],
    [InitNone, Always, TestOutputInt (
       [["part_disk"; "/dev/sda"; "mbr"];
        ["mkfs"; "ntfs"; "/dev/sda1"];
@@ -2664,7 +2665,7 @@ It is just a wrapper around the C L<glob(3)> function
 with flags C<GLOB_MARK|GLOB_BRACE>.
 See that manual page for more details.");
 
-  ("scrub_device", (RErr, [Device "device"]), 114, [DangerWillRobinson],
+  ("scrub_device", (RErr, [Device "device"]), 114, [DangerWillRobinson; Optional "scrub"],
    [InitNone, Always, TestRun (	(* use /dev/sdc because it's smaller *)
       [["scrub_device"; "/dev/sdc"]])],
    "scrub (securely wipe) a device",
@@ -2675,7 +2676,7 @@ more difficult.
 It is an interface to the L<scrub(1)> program.  See that
 manual page for more details.");
 
-  ("scrub_file", (RErr, [Pathname "file"]), 115, [],
+  ("scrub_file", (RErr, [Pathname "file"]), 115, [Optional "scrub"],
    [InitBasicFS, Always, TestRun (
       [["write_file"; "/file"; "content"; "0"];
        ["scrub_file"; "/file"]])],
@@ -2689,7 +2690,7 @@ The file is I<removed> after scrubbing.
 It is an interface to the L<scrub(1)> program.  See that
 manual page for more details.");
 
-  ("scrub_freespace", (RErr, [Pathname "dir"]), 116, [],
+  ("scrub_freespace", (RErr, [Pathname "dir"]), 116, [Optional "scrub"],
    [], (* XXX needs testing *)
    "scrub (securely wipe) free space",
    "\
@@ -2884,7 +2885,7 @@ Note that you cannot attach a swap label to a block device
 (eg. C</dev/sda>), just to a partition.  This appears to be
 a limitation of the kernel or swap tools.");
 
-  ("mkswap_U", (RErr, [String "uuid"; Device "device"]), 132, [],
+  ("mkswap_U", (RErr, [String "uuid"; Device "device"]), 132, [Optional "linuxfsuuid"],
    (let uuid = uuidgen () in
     [InitEmpty, Always, TestRun (
        [["part_disk"; "/dev/sda"; "mbr"];
@@ -2893,7 +2894,7 @@ a limitation of the kernel or swap tools.");
    "\
 Create a swap partition on C<device> with UUID C<uuid>.");
 
-  ("mknod", (RErr, [Int "mode"; Int "devmajor"; Int "devminor"; Pathname "path"]), 133, [],
+  ("mknod", (RErr, [Int "mode"; Int "devmajor"; Int "devminor"; Pathname "path"]), 133, [Optional "mknod"],
    [InitBasicFS, Always, TestOutputStruct (
       [["mknod"; "0o10777"; "0"; "0"; "/node"];
        (* NB: default umask 022 means 0777 -> 0755 in these tests *)
@@ -2911,7 +2912,7 @@ constants.  C<devmajor> and C<devminor> are the
 device major and minor numbers, only used when creating block
 and character special devices.");
 
-  ("mkfifo", (RErr, [Int "mode"; Pathname "path"]), 134, [],
+  ("mkfifo", (RErr, [Int "mode"; Pathname "path"]), 134, [Optional "mknod"],
    [InitBasicFS, Always, TestOutputStruct (
       [["mkfifo"; "0o777"; "/node"];
        ["stat"; "/node"]], [CompareWithInt ("mode", 0o10755)])],
@@ -2921,7 +2922,7 @@ This call creates a FIFO (named pipe) called C<path> with
 mode C<mode>.  It is just a convenient wrapper around
 C<guestfs_mknod>.");
 
-  ("mknod_b", (RErr, [Int "mode"; Int "devmajor"; Int "devminor"; Pathname "path"]), 135, [],
+  ("mknod_b", (RErr, [Int "mode"; Int "devmajor"; Int "devminor"; Pathname "path"]), 135, [Optional "mknod"],
    [InitBasicFS, Always, TestOutputStruct (
       [["mknod_b"; "0o777"; "99"; "66"; "/node"];
        ["stat"; "/node"]], [CompareWithInt ("mode", 0o60755)])],
@@ -2931,7 +2932,7 @@ This call creates a block device node called C<path> with
 mode C<mode> and device major/minor C<devmajor> and C<devminor>.
 It is just a convenient wrapper around C<guestfs_mknod>.");
 
-  ("mknod_c", (RErr, [Int "mode"; Int "devmajor"; Int "devminor"; Pathname "path"]), 136, [],
+  ("mknod_c", (RErr, [Int "mode"; Int "devmajor"; Int "devminor"; Pathname "path"]), 136, [Optional "mknod"],
    [InitBasicFS, Always, TestOutputStruct (
       [["mknod_c"; "0o777"; "99"; "66"; "/node"];
        ["stat"; "/node"]], [CompareWithInt ("mode", 0o20755)])],
@@ -3046,7 +3047,7 @@ C<method> must be one of C<gzip>, C<compress> or C<bzip2>.
 Since 1.0.63, use C<guestfs_file> instead which can now
 process compressed files.");
 
-  ("getxattrs", (RStructList ("xattrs", "xattr"), [Pathname "path"]), 141, [],
+  ("getxattrs", (RStructList ("xattrs", "xattr"), [Pathname "path"]), 141, [Optional "linuxxattrs"],
    [],
    "list extended attributes of a file or directory",
    "\
@@ -3058,7 +3059,7 @@ L<listxattr(2)> and L<getxattr(2)> calls.
 
 See also: C<guestfs_lgetxattrs>, L<attr(5)>.");
 
-  ("lgetxattrs", (RStructList ("xattrs", "xattr"), [Pathname "path"]), 142, [],
+  ("lgetxattrs", (RStructList ("xattrs", "xattr"), [Pathname "path"]), 142, [Optional "linuxxattrs"],
    [],
    "list extended attributes of a file or directory",
    "\
@@ -3068,7 +3069,7 @@ of the link itself.");
 
   ("setxattr", (RErr, [String "xattr";
                        String "val"; Int "vallen"; (* will be BufferIn *)
-                       Pathname "path"]), 143, [],
+                       Pathname "path"]), 143, [Optional "linuxxattrs"],
    [],
    "set extended attribute of a file or directory",
    "\
@@ -3080,7 +3081,7 @@ See also: C<guestfs_lsetxattr>, L<attr(5)>.");
 
   ("lsetxattr", (RErr, [String "xattr";
                         String "val"; Int "vallen"; (* will be BufferIn *)
-                        Pathname "path"]), 144, [],
+                        Pathname "path"]), 144, [Optional "linuxxattrs"],
    [],
    "set extended attribute of a file or directory",
    "\
@@ -3088,7 +3089,7 @@ This is the same as C<guestfs_setxattr>, but if C<path>
 is a symbolic link, then it sets an extended attribute
 of the link itself.");
 
-  ("removexattr", (RErr, [String "xattr"; Pathname "path"]), 145, [],
+  ("removexattr", (RErr, [String "xattr"; Pathname "path"]), 145, [Optional "linuxxattrs"],
    [],
    "remove extended attribute of a file or directory",
    "\
@@ -3097,7 +3098,7 @@ of the file C<path>.
 
 See also: C<guestfs_lremovexattr>, L<attr(5)>.");
 
-  ("lremovexattr", (RErr, [String "xattr"; Pathname "path"]), 146, [],
+  ("lremovexattr", (RErr, [String "xattr"; Pathname "path"]), 146, [Optional "linuxxattrs"],
    [],
    "remove extended attribute of a file or directory",
    "\
@@ -3397,7 +3398,7 @@ See C<guestfs_swapon_device> for other notes.");
 This command disables the libguestfs appliance swap on
 labeled swap partition.");
 
-  ("swapon_uuid", (RErr, [String "uuid"]), 176, [],
+  ("swapon_uuid", (RErr, [String "uuid"]), 176, [Optional "linuxfsuuid"],
    (let uuid = uuidgen () in
     [InitEmpty, Always, TestRun (
        [["mkswap_U"; uuid; "/dev/sdb"];
@@ -3408,7 +3409,7 @@ labeled swap partition.");
 This command enables swap to a swap partition with the given UUID.
 See C<guestfs_swapon_device> for other notes.");
 
-  ("swapoff_uuid", (RErr, [String "uuid"]), 177, [],
+  ("swapoff_uuid", (RErr, [String "uuid"]), 177, [Optional "linuxfsuuid"],
    [], (* XXX tested by swapon_uuid *)
    "disable swap on swap partition by UUID",
    "\
@@ -3426,7 +3427,7 @@ Create a swap file.
 This command just writes a swap file signature to an existing
 file.  To create the file itself, use something like C<guestfs_fallocate>.");
 
-  ("inotify_init", (RErr, [Int "maxevents"]), 179, [],
+  ("inotify_init", (RErr, [Int "maxevents"]), 179, [Optional "inotify"],
    [InitISOFS, Always, TestRun (
       [["inotify_init"; "0"]])],
    "create an inotify handle",
@@ -3467,7 +3468,7 @@ as exposed by the Linux kernel, which is roughly what we expose
 via libguestfs.  Note that there is one global inotify handle
 per libguestfs instance.");
 
-  ("inotify_add_watch", (RInt64 "wd", [Pathname "path"; Int "mask"]), 180, [],
+  ("inotify_add_watch", (RInt64 "wd", [Pathname "path"; Int "mask"]), 180, [Optional "inotify"],
    [InitBasicFS, Always, TestOutputList (
       [["inotify_init"; "0"];
        ["inotify_add_watch"; "/"; "1073741823"];
@@ -3486,14 +3487,14 @@ Note for non-C or non-Linux callers: the inotify events are
 defined by the Linux kernel ABI and are listed in
 C</usr/include/sys/inotify.h>.");
 
-  ("inotify_rm_watch", (RErr, [Int(*XXX64*) "wd"]), 181, [],
+  ("inotify_rm_watch", (RErr, [Int(*XXX64*) "wd"]), 181, [Optional "inotify"],
    [],
    "remove an inotify watch",
    "\
 Remove a previously defined inotify watch.
 See C<guestfs_inotify_add_watch>.");
 
-  ("inotify_read", (RStructList ("events", "inotify_event"), []), 182, [],
+  ("inotify_read", (RStructList ("events", "inotify_event"), []), 182, [Optional "inotify"],
    [],
    "return list of inotify events",
    "\
@@ -3508,7 +3509,7 @@ returns an empty list.  The reason is that the call will
 read events up to the maximum appliance-to-host message
 size and leave remaining events in the queue.");
 
-  ("inotify_files", (RStringList "paths", []), 183, [],
+  ("inotify_files", (RStringList "paths", []), 183, [Optional "inotify"],
    [],
    "return list of watched files that had events",
    "\
@@ -3516,7 +3517,7 @@ This function is a helpful wrapper around C<guestfs_inotify_read>
 which just returns a list of pathnames of objects that were
 touched.  The returned pathnames are sorted and deduplicated.");
 
-  ("inotify_close", (RErr, []), 184, [],
+  ("inotify_close", (RErr, []), 184, [Optional "inotify"],
    [],
    "close the inotify handle",
    "\
@@ -3524,7 +3525,7 @@ This closes the inotify handle which was previously
 opened by inotify_init.  It removes all watches, throws
 away any pending events, and deallocates all resources.");
 
-  ("setcon", (RErr, [String "context"]), 185, [],
+  ("setcon", (RErr, [String "context"]), 185, [Optional "selinux"],
    [],
    "set SELinux security context",
    "\
@@ -3533,7 +3534,7 @@ to the string C<context>.
 
 See the documentation about SELINUX in L<guestfs(3)>.");
 
-  ("getcon", (RString "context", []), 186, [],
+  ("getcon", (RString "context", []), 186, [Optional "selinux"],
    [],
    "get SELinux security context",
    "\
@@ -3583,7 +3584,7 @@ to the command:
    "\
 This creates an ext2 external journal on C<device> with label C<label>.");
 
-  ("mke2journal_U", (RErr, [Int "blocksize"; String "uuid"; Device "device"]), 190, [],
+  ("mke2journal_U", (RErr, [Int "blocksize"; String "uuid"; Device "device"]), 190, [Optional "linuxfsuuid"],
    (let uuid = uuidgen () in
     [InitEmpty, Always, TestOutput (
        [["sfdiskM"; "/dev/sda"; ",100 ,"];
@@ -3617,7 +3618,7 @@ an external journal on the journal labeled C<label>.
 
 See also C<guestfs_mke2journal_L>.");
 
-  ("mke2fs_JU", (RErr, [String "fstype"; Int "blocksize"; Device "device"; String "uuid"]), 193, [],
+  ("mke2fs_JU", (RErr, [String "fstype"; Int "blocksize"; Device "device"; String "uuid"]), 193, [Optional "linuxfsuuid"],
    [],
    "make ext2/3/4 filesystem with external journal",
    "\
@@ -3626,7 +3627,7 @@ an external journal on the journal with UUID C<uuid>.
 
 See also C<guestfs_mke2journal_U>.");
 
-  ("modprobe", (RErr, [String "modulename"]), 194, [],
+  ("modprobe", (RErr, [String "modulename"]), 194, [Optional "linuxmodules"],
    [InitNone, Always, TestRun [["modprobe"; "fat"]]],
    "load a kernel module",
    "\
@@ -3838,7 +3839,7 @@ might cause the protocol message size to be exceeded, causing
 this call to fail.  The caller must split up such requests
 into smaller groups of names.");
 
-  ("lxattrlist", (RStructList ("xattrs", "xattr"), [Pathname "path"; StringList "names"]), 205, [],
+  ("lxattrlist", (RStructList ("xattrs", "xattr"), [Pathname "path"; StringList "names"]), 205, [Optional "linuxxattrs"],
    [], (* XXX *)
    "lgetxattr on multiple files",
    "\
@@ -4115,8 +4116,8 @@ The precise libguestfs function groups that may be checked by this
 command are listed in L<guestfs(3)/AVAILABILITY>.
 
 The argument C<groups> is a list of API group names, eg:
-C<[\"inotify\", \"part\"]> would check for the availability of
-the C<guestfs_inotify_*> functions and C<guestfs_part_*>
+C<[\"inotify\", \"augeas\"]> would check for the availability of
+the C<guestfs_inotify_*> functions and C<guestfs_aug_*>
 (partition editing) functions.
 
 The command returns no error if I<all> requested groups are available.
@@ -4596,6 +4597,26 @@ with correct use of these functions." alt in
   with
     Not_found -> None
 
+(* Create list of optional groups. *)
+let optgroups =
+  let h = Hashtbl.create 13 in
+  List.iter (
+    fun (name, _, _, flags, _, _, _) ->
+      List.iter (
+        function
+        | Optional group ->
+            let names = try Hashtbl.find h group with Not_found -> [] in
+            Hashtbl.replace h group (name :: names)
+        | _ -> ()
+      ) flags
+  ) daemon_functions;
+  let groups = Hashtbl.fold (fun k _ ks -> k :: ks) h [] in
+  let groups =
+    List.map (
+      fun group -> group, List.sort compare (Hashtbl.find h group)
+    ) groups in
+  List.sort (fun x y -> compare (fst x) (fst y)) groups
+
 (* Check function names etc. for consistency. *)
 let check_functions () =
   let contains_uppercase str =
@@ -4919,6 +4940,21 @@ and generate_structs_pod () =
       pr "\n"
   ) structs
 
+and generate_availability_pod () =
+  (* Availability documentation. *)
+  pr "=over 4\n";
+  pr "\n";
+  List.iter (
+    fun (group, functions) ->
+      pr "=item B<%s>\n" group;
+      pr "\n";
+      pr "The following functions:\n";
+      List.iter (pr "L</guestfs_%s>\n") functions;
+      pr "\n"
+  ) optgroups;
+  pr "=back\n";
+  pr "\n"
+
 (* Generate the protocol (XDR) file, 'guestfs_protocol.x' and
  * indirectly 'guestfs_protocol.h' and 'guestfs_protocol.c'.
  *
@@ -5934,6 +5970,34 @@ and generate_daemon_names () =
   ) daemon_functions;
   pr "};\n";
 
+(* Generate the optional groups for the daemon to implement
+ * guestfs_available.
+ *)
+and generate_daemon_optgroups_c () =
+  generate_header CStyle GPLv2;
+
+  pr "#include <config.h>\n";
+  pr "\n";
+  pr "#include \"daemon.h\"\n";
+  pr "#include \"optgroups.h\"\n";
+  pr "\n";
+
+  pr "struct optgroup optgroups[] = {\n";
+  List.iter (
+    fun (group, _) ->
+      pr "  { \"%s\", optgroup_%s_available },\n" group group
+  ) optgroups;
+  pr "  { NULL, NULL }\n";
+  pr "};\n"
+
+and generate_daemon_optgroups_h () =
+  generate_header CStyle GPLv2;
+
+  List.iter (
+    fun (group, _) ->
+      pr "extern int optgroup_%s_available (void);\n" group
+  ) optgroups
+
 (* Generate the tests. *)
 and generate_tests () =
   generate_header CStyle GPLv2;
@@ -10302,6 +10366,14 @@ Run it from the top source directory using the command
   generate_daemon_names ();
   close ();
 
+  let close = output_to "daemon/optgroups.c" in
+  generate_daemon_optgroups_c ();
+  close ();
+
+  let close = output_to "daemon/optgroups.h" in
+  generate_daemon_optgroups_h ();
+  close ();
+
   let close = output_to "capitests/tests.c" in
   generate_tests ();
   close ();
@@ -10326,6 +10398,10 @@ Run it from the top source directory using the command
   generate_actions_pod ();
   close ();
 
+  let close = output_to "guestfs-availability.pod" in
+  generate_availability_pod ();
+  close ();
+
   let close = output_to "guestfish-actions.pod" in
   generate_fish_actions_pod ();
   close ();