diff --git a/Makefile.am b/Makefile.am
index 4e476ea92..50bfb322f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -52,6 +52,7 @@ SUBDIRS += tests/9p
 SUBDIRS += tests/rsync
 SUBDIRS += tests/bigdirs
 SUBDIRS += tests/disk-labels
+SUBDIRS += tests/hotplug
 SUBDIRS += tests/regressions
 endif
 
diff --git a/configure.ac b/configure.ac
index 0422bcb40..b4720bce3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1379,6 +1379,7 @@ AC_CONFIG_FILES([Makefile
                  tests/disk-labels/Makefile
                  tests/extra/Makefile
                  tests/guests/Makefile
+                 tests/hotplug/Makefile
                  tests/luks/Makefile
                  tests/lvm/Makefile
                  tests/md/Makefile
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index 2a25c695f..9ffff152b 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -125,6 +125,7 @@ guestfsd_SOURCES = \
 	guestfsd.c \
 	headtail.c \
 	hexdump.c \
+	hotplug.c \
 	hivex.c \
 	htonl.c \
 	initrd.c \
diff --git a/daemon/hotplug.c b/daemon/hotplug.c
new file mode 100644
index 000000000..aae638e7a
--- /dev/null
+++ b/daemon/hotplug.c
@@ -0,0 +1,67 @@
+/* libguestfs - the guestfsd daemon
+ * Copyright (C) 2012 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <time.h>
+
+#include "guestfs_protocol.h"
+#include "daemon.h"
+#include "actions.h"
+
+#define HOT_ADD_TIMEOUT 30 /* seconds */
+
+/* Wait for /dev/disk/guestfs/<label> to appear.  Timeout (and error)
+ * if it doesn't appear after a reasonable length of time.
+ */
+int
+do_internal_hot_add_drive (const char *label)
+{
+  time_t start_t, now_t;
+  size_t len = strlen (label);
+  char path[len+64];
+  int r;
+
+  snprintf (path, len+64, "/dev/disk/guestfs/%s", label);
+
+  time (&start_t);
+
+  while (time (&now_t) - start_t <= HOT_ADD_TIMEOUT) {
+    udev_settle ();
+
+    r = access (path, F_OK);
+    if (r == -1 && errno != ENOENT) {
+      reply_with_perror ("%s", path);
+      return -1;
+    }
+    if (r == 0)
+      return 0;
+
+    sleep (1);
+  }
+
+  reply_with_error ("hot-add drive: '%s' did not appear after %d seconds: "
+                    "this could mean that virtio-scsi (in qemu or kernel) "
+                    "or udev is not working",
+                    path, HOT_ADD_TIMEOUT);
+  return -1;
+}
diff --git a/fish/alloc.c b/fish/alloc.c
index f6e5b8ff7..7454fb737 100644
--- a/fish/alloc.c
+++ b/fish/alloc.c
@@ -72,11 +72,6 @@ alloc_disk (const char *filename, const char *size_str, int add, int sparse)
   if (parse_size (size_str, &size) == -1)
     return -1;
 
-  if (!guestfs_is_config (g)) {
-    fprintf (stderr, _("can't allocate or add disks after launching\n"));
-    return -1;
-  }
-
   fd = open (filename, O_WRONLY|O_CREAT|O_NOCTTY|O_TRUNC|O_CLOEXEC, 0666);
   if (fd == -1) {
     perror (filename);
diff --git a/generator/actions.ml b/generator/actions.ml
index 25d28098f..39c71ab8b 100644
--- a/generator/actions.ml
+++ b/generator/actions.ml
@@ -1186,14 +1186,22 @@ not all belong to a single logical operating system
     name = "add_drive";
     style = RErr, [String "filename"], [OBool "readonly"; OString "format"; OString "iface"; OString "name"; OString "label"];
     once_had_no_optargs = true;
-    fish_alias = ["add"]; config_only = true;
+    fish_alias = ["add"];
     shortdesc = "add an image to examine or modify";
     longdesc = "\
 This function adds a disk image called C<filename> to the handle.
 C<filename> may be a regular host file or a host device.
 
-The first time you call this function, the disk appears as
-C</dev/sda>, the second time as C</dev/sdb>, and so on.
+When this function is called before C<guestfs_launch> (the
+usual case) then the first time you call this function,
+the disk appears in the API as C</dev/sda>, the second time
+as C</dev/sdb>, and so on.
+
+In libguestfs E<ge> 1.20 you can also call this function
+after launch (with some restrictions).  This is called
+\"hotplugging\".  When hotplugging, you must specify a
+C<label> so that the new disk gets a predictable name.
+For more information see L<guestfs(3)/HOTPLUGGING>.
 
 You don't necessarily need to be root when using libguestfs.  However
 you obviously do need sufficient permissions to access the filename
@@ -9951,6 +9959,16 @@ This returns a hashtable, where keys are the disk labels
 are the full raw block device and partition names
 (eg. C</dev/sda> and C</dev/sda1>)." };
 
+  { defaults with
+    name = "internal_hot_add_drive";
+    style = RErr, [String "label"], [];
+    proc_nr = Some 370;
+    in_fish = false; in_docs = false;
+    tests = [];
+    shortdesc = "internal hotplugging operation";
+    longdesc = "\
+This function is used internally when hotplugging drives." };
+
 ]
 
 (* Non-API meta-commands available only in guestfish.
diff --git a/po/POTFILES b/po/POTFILES
index 548156c47..22cd1486e 100644
--- a/po/POTFILES
+++ b/po/POTFILES
@@ -42,6 +42,7 @@ daemon/guestfsd.c
 daemon/headtail.c
 daemon/hexdump.c
 daemon/hivex.c
+daemon/hotplug.c
 daemon/htonl.c
 daemon/initrd.c
 daemon/inotify.c
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index 446dfcc54..5b0cffbc0 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-369
+370
diff --git a/src/guestfs-internal.h b/src/guestfs-internal.h
index ed9ada48c..db9818c3b 100644
--- a/src/guestfs-internal.h
+++ b/src/guestfs-internal.h
@@ -166,6 +166,9 @@ struct attach_ops {
 
   int (*get_pid) (guestfs_h *g);         /* get-pid API. */
   int (*max_disks) (guestfs_h *g);       /* max-disks API. */
+
+  /* Hotplugging drives. */
+  int (*hot_add_drive) (guestfs_h *g, struct drive *drv, size_t drv_index);
 };
 extern struct attach_ops attach_ops_appliance;
 extern struct attach_ops attach_ops_libvirt;
diff --git a/src/guestfs.pod b/src/guestfs.pod
index 48d810b0b..624e743e1 100644
--- a/src/guestfs.pod
+++ b/src/guestfs.pod
@@ -143,8 +143,11 @@ one you added), etc.
 
 Once L</guestfs_launch> has been called you cannot add any more images.
 You can call L</guestfs_list_devices> to get a list of the device
-names, in the order that you added them.  See also L</BLOCK DEVICE
-NAMING> below.
+names, in the order that you added them.
+See also L</BLOCK DEVICE NAMING> below.
+
+There are slightly different rules when hotplugging disks (in
+libguestfs E<ge> 1.20).  See L</HOTPLUGGING> below.
 
 =head2 MOUNTING
 
@@ -601,6 +604,35 @@ Libguestfs on top of FUSE performs quite poorly.  For best performance
 do not use it.  Use ordinary libguestfs filesystem calls, upload,
 download etc. instead.
 
+=head2 HOTPLUGGING
+
+In libguestfs E<ge> 1.20, you may add drives after calling
+L</guestfs_launch>.  There are some restrictions, see below.
+This is called I<hotplugging>.
+
+Only a subset of the attach-method backends support hotplugging
+(currently only the libvirt attach-method has support).  It also
+requires that you use libvirt E<ge> 0.10.3 and qemu E<ge> 1.2.
+
+To hot-add a disk, simply call L</guestfs_add_drive_opts> after
+L</guestfs_launch>.  It is mandatory to specify the C<label> parameter
+so that the newly added disk has a predictable name.  For example:
+
+ if (guestfs_launch (g) == -1)
+   error ("launch failed");
+ 
+ if (guestfs_add_drive_opts (g, filename,
+                             GUESTFS_ADD_DRIVE_OPTS_LABEL, "newdisk",
+                             -1) == -1)
+   error ("hot-add of disk failed");
+ 
+ if (guestfs_part_disk ("/dev/disk/guestfs/newdisk", "mbr") == -1)
+   error ("partitioning of hot-added disk failed");
+
+Backends that support hotplugging do not require that you add
+E<ge> 1 disk before calling launch.  When hotplugging is supported
+you don't need to add any disks.
+
 =head2 INSPECTION
 
 Libguestfs has APIs for inspecting an unknown disk image to find out
@@ -2639,7 +2671,7 @@ The guest may be killed by L</guestfs_kill_subprocess>, or may die
 asynchronously at any time (eg. due to some internal error), and that
 causes the state to transition back to CONFIG.
 
-Configuration commands for qemu such as L</guestfs_add_drive> can only
+Configuration commands for qemu such as L</guestfs_set_path> can only
 be issued when in the CONFIG state.
 
 The API offers one call that goes from CONFIG through LAUNCHING to
diff --git a/src/launch-libvirt.c b/src/launch-libvirt.c
index aa1c39f23..3eab56766 100644
--- a/src/launch-libvirt.c
+++ b/src/launch-libvirt.c
@@ -135,14 +135,6 @@ launch_libvirt (guestfs_h *g, const char *libvirt_uri)
   struct drive *drv;
   size_t i;
 
-  /* At present you must add drives before starting the appliance.  In
-   * future when we enable hotplugging you won't need to do this.
-   */
-  if (!g->nr_drives) {
-    error (g, _("you must call guestfs_add_drive before guestfs_launch"));
-    return -1;
-  }
-
   /* XXX: It should be possible to make this work. */
   if (g->direct) {
     error (g, _("direct mode flag is not supported yet for libvirt attach method"));
@@ -1376,6 +1368,89 @@ max_disks_libvirt (guestfs_h *g)
   return 255;
 }
 
+static xmlChar *construct_libvirt_xml_hot_add_disk (guestfs_h *g, struct drive *drv, size_t drv_index);
+
+/* Hot-add a drive.  Note the appliance is up when this is called. */
+static int
+hot_add_drive_libvirt (guestfs_h *g, struct drive *drv, size_t drv_index)
+{
+  virConnectPtr conn = g->virt.connv;
+  virDomainPtr dom = g->virt.domv;
+  xmlChar *xml = NULL;
+
+  if (!conn || !dom) {
+    /* This is essentially an internal error if it happens. */
+    error (g, "%s: conn == NULL or dom == NULL", __func__);
+    return -1;
+  }
+
+  /* Create overlay for read-only drive.  This works around lack of
+   * support for <transient/> disks in libvirt.
+   */
+  if (make_qcow2_overlay_for_drive (g, drv) == -1)
+    return -1;
+
+  /* Create the XML for the new disk. */
+  xml = construct_libvirt_xml_hot_add_disk (g, drv, drv_index);
+  if (xml == NULL)
+    return -1;
+
+  /* Attach it. */
+  if (virDomainAttachDeviceFlags (dom, (char *) xml,
+                                  VIR_DOMAIN_DEVICE_MODIFY_LIVE) == -1) {
+    libvirt_error (g, _("could not attach disk to libvirt domain"));
+    goto error;
+  }
+
+  free (xml);
+  return 0;
+
+ error:
+  free (xml);
+  return -1;
+}
+
+static xmlChar *
+construct_libvirt_xml_hot_add_disk (guestfs_h *g, struct drive *drv,
+                                    size_t drv_index)
+{
+  xmlChar *ret = NULL;
+  xmlBufferPtr xb = NULL;
+  xmlOutputBufferPtr ob;
+  xmlTextWriterPtr xo = NULL;
+
+  XMLERROR (NULL, xb = xmlBufferCreate ());
+  XMLERROR (NULL, ob = xmlOutputBufferCreateBuffer (xb, NULL));
+  XMLERROR (NULL, xo = xmlNewTextWriter (ob));
+
+  XMLERROR (-1, xmlTextWriterSetIndent (xo, 1));
+  XMLERROR (-1, xmlTextWriterSetIndentString (xo, BAD_CAST "  "));
+  XMLERROR (-1, xmlTextWriterStartDocument (xo, NULL, NULL, NULL));
+
+  if (construct_libvirt_xml_disk (g, xo, drv, drv_index) == -1)
+    goto err;
+
+  XMLERROR (-1, xmlTextWriterEndDocument (xo));
+  XMLERROR (NULL, ret = xmlBufferDetach (xb)); /* caller frees ret */
+
+  debug (g, "hot-add disk XML:\n%s", ret);
+
+ err:
+  if (xo)
+    xmlFreeTextWriter (xo); /* frees 'ob' too */
+  if (xb)
+    xmlBufferFree (xb);
+
+  return ret;
+}
+
+struct attach_ops attach_ops_libvirt = {
+  .launch = launch_libvirt,
+  .shutdown = shutdown_libvirt,
+  .max_disks = max_disks_libvirt,
+  .hot_add_drive = hot_add_drive_libvirt,
+};
+
 #else /* no libvirt or libxml2 at compile time */
 
 #define NOT_IMPL(r)                                                     \
@@ -1403,10 +1478,16 @@ max_disks_libvirt (guestfs_h *g)
   NOT_IMPL (-1);
 }
 
-#endif /* no libvirt or libxml2 at compile time */
+static int
+hot_add_drive_libvirt (guestfs_h *g, struct drive *drv, size_t drv_index)
+{
+  NOT_IMPL (-1);
+}
 
 struct attach_ops attach_ops_libvirt = {
   .launch = launch_libvirt,
   .shutdown = shutdown_libvirt,
   .max_disks = max_disks_libvirt,
 };
+
+#endif /* no libvirt or libxml2 at compile time */
diff --git a/src/launch.c b/src/launch.c
index 1b6cf4bdb..a4e10fefc 100644
--- a/src/launch.c
+++ b/src/launch.c
@@ -29,6 +29,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <errno.h>
+#include <assert.h>
 
 #include "c-ctype.h"
 
@@ -57,14 +58,29 @@ guestfs___rollback_drives (guestfs_h *g, size_t old_i)
   g->nr_drives = old_i;
 }
 
+/* Add struct drive to the g->drives vector at the given index. */
+static void
+add_drive_to_handle_at (guestfs_h *g, struct drive *d, size_t drv_index)
+{
+  if (drv_index >= g->nr_drives) {
+    g->drives = safe_realloc (g, g->drives,
+                              sizeof (struct drive *) * (drv_index + 1));
+    while (g->nr_drives <= drv_index) {
+      g->drives[g->nr_drives] = NULL;
+      g->nr_drives++;
+    }
+  }
+
+  assert (g->drives[drv_index] == NULL);
+
+  g->drives[drv_index] = d;
+}
+
 /* Add struct drive to the end of the g->drives vector in the handle. */
 static void
 add_drive_to_handle (guestfs_h *g, struct drive *d)
 {
-  g->nr_drives++;
-  g->drives = safe_realloc (g, g->drives,
-                            sizeof (struct drive *) * g->nr_drives);
-  g->drives[g->nr_drives-1] = d;
+  add_drive_to_handle_at (g, d, g->nr_drives);
 }
 
 static struct drive *
@@ -207,6 +223,48 @@ valid_disk_label (const char *str)
   return 1;
 }
 
+/* The low-level function that adds a drive. */
+static int
+add_drive (guestfs_h *g, struct drive *drv)
+{
+  size_t i, drv_index;
+
+  if (g->state == CONFIG) {
+    /* Not hotplugging, so just add it to the handle. */
+    add_drive_to_handle (g, drv);
+    return 0;
+  }
+
+  /* ... else, hotplugging case. */
+  if (!g->attach_ops || !g->attach_ops->hot_add_drive) {
+    error (g, _("the current attach-method does not support hotplugging drives"));
+    return -1;
+  }
+
+  if (!drv->disk_label) {
+    error (g, _("'label' is required when hotplugging drives"));
+    return -1;
+  }
+
+  /* Get the first free index, or add it at the end. */
+  drv_index = g->nr_drives;
+  for (i = 0; i < g->nr_drives; ++i)
+    if (g->drives[i] == NULL)
+      drv_index = i;
+
+  /* Hot-add the drive. */
+  if (g->attach_ops->hot_add_drive (g, drv, drv_index) == -1)
+    return -1;
+
+  add_drive_to_handle_at (g, drv, drv_index);
+
+  /* Call into the appliance to wait for the new drive to appear. */
+  if (guestfs_internal_hot_add_drive (g, drv->disk_label) == -1)
+    return -1;
+
+  return 0;
+}
+
 /* Traditionally you have been able to use /dev/null as a filename, as
  * many times as you like.  Ancient KVM (RHEL 5) cannot handle adding
  * /dev/null readonly.  qemu 1.2 + virtio-scsi segfaults when you use
@@ -220,7 +278,7 @@ add_null_drive (guestfs_h *g, int readonly, const char *format,
                 const char *iface, const char *name, const char *disk_label)
 {
   char *tmpfile = NULL;
-  int fd = -1;
+  int fd = -1, r;
   struct drive *drv;
 
   if (format && STRNEQ (format, "raw")) {
@@ -252,8 +310,12 @@ add_null_drive (guestfs_h *g, int readonly, const char *format,
   }
 
   drv = create_drive_struct (g, tmpfile, readonly, format, iface, name, disk_label, 0);
-  add_drive_to_handle (g, drv);
+  r = add_drive (g, drv);
   free (tmpfile);
+  if (r == -1) {
+    free_drive_struct (drv);
+    return -1;
+  }
 
   return 0;
 
@@ -328,7 +390,11 @@ guestfs__add_drive_opts (guestfs_h *g, const char *filename,
 
   drv = create_drive_struct (g, filename, readonly, format, iface, name, disk_label,
                              use_cache_none);
-  add_drive_to_handle (g, drv);
+  if (add_drive (g, drv) == -1) {
+    free_drive_struct (drv);
+    return -1;
+  }
+
   return 0;
 }
 
diff --git a/tests/hotplug/Makefile.am b/tests/hotplug/Makefile.am
new file mode 100644
index 000000000..6644930ab
--- /dev/null
+++ b/tests/hotplug/Makefile.am
@@ -0,0 +1,26 @@
+# libguestfs
+# Copyright (C) 2012 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+include $(top_srcdir)/subdir-rules.mk
+
+TESTS = \
+	test-hot-add.pl
+
+TESTS_ENVIRONMENT = $(top_builddir)/run --test
+
+EXTRA_DIST = \
+	$(TESTS)
diff --git a/tests/hotplug/test-hot-add.pl b/tests/hotplug/test-hot-add.pl
new file mode 100755
index 000000000..b1322e889
--- /dev/null
+++ b/tests/hotplug/test-hot-add.pl
@@ -0,0 +1,66 @@
+#!/usr/bin/perl
+# Copyright (C) 2012 Red Hat Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+# Test hot-adding disks.
+
+use strict;
+use warnings;
+
+use Sys::Guestfs;
+
+my $g = Sys::Guestfs->new ();
+
+# Skip the test if the default attach-method isn't libvirt, since only
+# the libvirt backend supports hotplugging.
+my $attach_method = $g->get_attach_method ();
+unless ($attach_method eq "libvirt" || $attach_method =~ /^libvirt:/) {
+    print "$0: test skipped because attach-method ($attach_method) is not libvirt\n";
+    exit 77
+}
+
+# We don't need to add disks before launch.
+$g->launch ();
+
+# Create some temporary disks.
+open FILE, ">test1.img" or die "test1.img: $!";
+truncate FILE, 512 * 1024 * 1024 or die "test1.img: truncate: $!";
+close FILE;
+
+open FILE, ">test2.img" or die "test2.img: $!";
+truncate FILE, 512 * 1024 * 1024 or die "test2.img: truncate: $!";
+close FILE;
+
+die unless system ("qemu-img create -f qcow2 test3.img 1G") == 0;
+
+# Hot-add them.  Labels are required.
+$g->add_drive ("test1.img", label => "a"); # autodetect format
+$g->add_drive ("test2.img", label => "b", format => "raw", readonly => 1);
+$g->add_drive ("test3.img", label => "c", format => "qcow2");
+
+# Check we can use the disks immediately.
+$g->part_disk ("/dev/disk/guestfs/a", "mbr");
+$g->mkfs ("ext2", "/dev/disk/guestfs/c");
+$g->mkfs ("ext2", "/dev/disk/guestfs/a1");
+
+$g->shutdown ();
+$g->close ();
+
+unlink "test1.img";
+unlink "test2.img";
+unlink "test3.img";
+
+exit 0