libostree: Add initial GRUB2 supportwip/grub2

In this approach, we drop a /etc/grub.d/15_ostree file which is a
hybrid of shell/C that picks up bits from the GRUB2 library (e.g. the
block device script generation), and then calls into libostree's
GRUB2 code which knows about the BLS entries.

This is admittedly ugly.  There exists another approach for GRUB2 to
learn the BLS specification.  However, the spec has a few issues:

https://www.redhat.com/archives/anaconda-devel-list/2014-July/msg00002.html

This approach also gives a bit more control to the admin via the
naming of the 15_ostree symlink; they can easily disable it:

Or reorder the ostree entries ahead of 10_linux:

Also, this approach doesn't require patches for grub2, which is an
issue with the pressure to backport (rpm-)OSTree to EL7.

19 files changed, 657 insertions, 11 deletions

diff --git a/Makefile-boot.am b/Makefile-boot.am
index 49b3c037..0a54da83 100644
--- a/Makefile-boot.am
+++ b/Makefile-boot.am
@@ -39,6 +39,16 @@ systemdsystemunit_DATA = src/boot/ostree-prepare-root.service \
 	src/boot/ostree-remount.service
 endif
 
+pkglibexec_SCRIPTS += src/boot/grub2-15_ostree
+
+if BUILDOPT_GRUB2
+install-grub2-config-hook:
+	mkdir -p $(DESTDIR)$(grub2configdir)
+	ln -sf $(pkglibexecdir)/grub2-15_ostree $(DESTDIR)$(grub2configdir)/15_ostree
+grub2configdir = $(sysconfdir)/grub.d
+INSTALL_DATA_HOOKS += install-grub2-config-hook
+endif
+
 EXTRA_DIST += src/boot/dracut/module-setup.sh \
 	src/boot/dracut/ostree.conf \
 	src/boot/mkinitcpio/ostree \
diff --git a/Makefile-decls.am b/Makefile-decls.am
index a57466cf..a5c9d503 100644
--- a/Makefile-decls.am
+++ b/Makefile-decls.am
@@ -30,6 +30,7 @@ sbin_PROGRAMS =
 bin_SCRIPTS =
 lib_LTLIBRARIES =
 libexec_PROGRAMS =
+pkglibexec_SCRIPTS =
 noinst_LTLIBRARIES =
 noinst_PROGRAMS =
 privlibdir = $(pkglibdir)
diff --git a/Makefile-libostree.am b/Makefile-libostree.am
index fbe173dc..4d1f9019 100644
--- a/Makefile-libostree.am
+++ b/Makefile-libostree.am
@@ -35,6 +35,8 @@ libostreeinclude_HEADERS = $(libostree_public_headers)
 
 libostree_1_la_SOURCES = \
 	src/libostree/ostree-async-progress.c \
+	src/libostree/ostree-cmdprivate.h \
+	src/libostree/ostree-cmdprivate.c \
 	src/libostree/ostree-core-private.h \
 	src/libostree/ostree-core.c \
 	src/libostree/ostree-checksum-input-stream.c \
@@ -74,6 +76,8 @@ libostree_1_la_SOURCES = \
 	src/libostree/ostree-deployment.c \
 	src/libostree/ostree-bootloader.h \
 	src/libostree/ostree-bootloader.c \
+	src/libostree/ostree-bootloader-grub2.h \
+	src/libostree/ostree-bootloader-grub2.c \
 	src/libostree/ostree-bootloader-syslinux.h \
 	src/libostree/ostree-bootloader-syslinux.c \
 	src/libostree/ostree-bootloader-uboot.h \
diff --git a/Makefile-ostree.am b/Makefile-ostree.am
index 47b06f1e..86ee144e 100644
--- a/Makefile-ostree.am
+++ b/Makefile-ostree.am
@@ -66,6 +66,7 @@ ostree_SOURCES += \
 	src/ostree/ot-admin-builtins.h \
 	src/ostree/ot-admin-instutil-builtin-selinux-ensure-labeled.c \
 	src/ostree/ot-admin-instutil-builtin-set-kargs.c \
+	src/ostree/ot-admin-instutil-builtin-grub2-generate.c \
 	src/ostree/ot-admin-instutil-builtins.h \
 	src/ostree/ot-admin-functions.h \
 	src/ostree/ot-admin-functions.c \
diff --git a/configure.ac b/configure.ac
index b812c40f..ce2bf025 100644
--- a/configure.ac
+++ b/configure.ac
@@ -201,6 +201,12 @@ AS_IF([test "x$with_dracut" = "xyes" || test "x$with_mkinitcpio" = "xyes"], [
 ])
 AM_CONDITIONAL(BUILDOPT_SYSTEMD, test x$with_systemd = xyes)
 
+AC_ARG_WITH(grub2,
+            AS_HELP_STRING([--with-grub2],
+                           [Install grub2 hook (default: yes)]),,
+              [with_grub2=yes])
+AM_CONDITIONAL(BUILDOPT_GRUB2, test x$with_grub2 = xyes)
+
 dnl for tests
 AS_IF([test "x$found_introspection" = xyes], [
   AC_PATH_PROG(GJS, [gjs])
diff --git a/packaging/ostree.spec.in b/packaging/ostree.spec.in
index 808a2ef3..265f3db4 100644
--- a/packaging/ostree.spec.in
+++ b/packaging/ostree.spec.in
@@ -46,6 +46,14 @@ Requires: %{name} = %{version}-%{release}
 %description devel
 The %{name}-devel package includes the header files for the %{name} library.
 
+%package grub2
+Summary: GRUB2 integration for OSTree
+Group: Development/Libraries
+Requires: grub2
+
+%description grub2
+GRUB2 integration for OSTree
+
 %prep
 %setup -q -n ostree-%{version}
 
@@ -94,3 +102,7 @@ rm -rf $RPM_BUILD_ROOT
 %dir %{_datadir}/gtk-doc/html/ostree
 %{_datadir}/gtk-doc/html/ostree
 %{_datadir}/gir-1.0/OSTree-1.0.gir
+
+%files grub2
+%{_sysconfdir}/grub.d/*ostree
+%{_libexecdir}/ostree/grub2*
diff --git a/src/boot/grub2-15_ostree b/src/boot/grub2-15_ostree
new file mode 100644
index 00000000..dfff6e89
--- /dev/null
+++ b/src/boot/grub2-15_ostree
@@ -0,0 +1,47 @@
+#!/bin/sh
+# 
+# Copyright (C) 2014 Colin Walters <walters@verbum.org>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License as published
+# by the Free Software Foundation; either version 2 of the licence or (at
+# your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General
+# Public License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+# Boston, MA 02111-1307, USA.
+
+# Gracefully exit if ostree is not installed
+if ! which ostree >/dev/null 2>/dev/null; then
+    exit 0
+fi
+
+# Make sure we're in the right environment
+if ! test -n "${GRUB_DEVICE}"; then
+    echo "This script must be run as a child of grub2-mkconfig" 1>&2
+    exit 1
+fi
+
+set -e
+
+# Pick up stuff from grub's helper that we want to inject into our
+# generated bootloader configuration.  Yes, this is pretty awful, but
+# it's a lot better than reimplementing the config-generating bits of
+# OSTree in shell script.
+
+. /usr/share/grub/grub-mkconfig_lib
+
+DEVICE=${GRUB_DEVICE_BOOT:-${GRUB_DEVICE}}
+
+GRUB2_BOOT_DEVICE_ID="$(grub_get_device_id ${DEVICE})"
+export GRUB2_BOOT_DEVICE_ID
+GRUB2_PREPARE_ROOT_CACHE="$(prepare_grub_to_access_device ${DEVICE})"
+export GRUB2_PREPARE_ROOT_CACHE
+
+exec ostree admin instutil grub2-generate
diff --git a/src/libostree/ostree-bootloader-grub2.c b/src/libostree/ostree-bootloader-grub2.c
new file mode 100644
index 00000000..fc2ac81f
--- /dev/null
+++ b/src/libostree/ostree-bootloader-grub2.c
@@ -0,0 +1,279 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "ostree-sysroot-private.h"
+#include "ostree-bootloader-grub2.h"
+#include "otutil.h"
+#include <gio/gfiledescriptorbased.h>
+#include <gio/gunixoutputstream.h>
+#include "libgsystem.h"
+
+#include <string.h>
+
+struct _OstreeBootloaderGrub2
+{
+  GObject       parent_instance;
+
+  OstreeSysroot  *sysroot;
+  GFile          *config_path_bios;
+};
+
+typedef GObjectClass OstreeBootloaderGrub2Class;
+
+static void _ostree_bootloader_grub2_bootloader_iface_init (OstreeBootloaderInterface *iface);
+G_DEFINE_TYPE_WITH_CODE (OstreeBootloaderGrub2, _ostree_bootloader_grub2, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (OSTREE_TYPE_BOOTLOADER, _ostree_bootloader_grub2_bootloader_iface_init));
+
+static gboolean
+_ostree_bootloader_grub2_query (OstreeBootloader *bootloader)
+{
+  OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (bootloader);
+
+  return g_file_query_exists (self->config_path_bios, NULL);
+}
+
+static const char *
+_ostree_bootloader_grub2_get_name (OstreeBootloader *bootloader)
+{
+  return "grub2";
+}
+
+gboolean
+_ostree_bootloader_grub2_generate_config (OstreeBootloaderGrub2         *self,
+                                          int                            bootversion,
+                                          int                            target_fd,
+                                          GCancellable                  *cancellable,
+                                          GError                       **error)
+{
+  gboolean ret = FALSE;
+  gs_unref_object GOutputStream *out_stream = NULL;
+  gs_unref_object GDataOutputStream *dataout = NULL;
+  gs_unref_ptrarray GPtrArray *loader_configs = NULL;
+  guint i;
+  gs_free char *kernel_arg = NULL;
+  /* So... yeah.  Just going to hardcode these. */
+  static const char hardcoded_video[] = "load_video\n"
+    "set gfxpayload=keep\n";
+  static const char hardcoded_insmods[] = "insmod gzio\n";
+  const char *grub2_boot_device_id =
+    g_getenv ("GRUB2_BOOT_DEVICE_ID");
+  const char *grub2_prepare_root_cache =
+    g_getenv ("GRUB2_PREPARE_ROOT_CACHE");
+
+  /* We must have been called via the wrapper script */
+  g_assert (grub2_boot_device_id != NULL);
+  g_assert (grub2_prepare_root_cache != NULL);
+
+  out_stream = g_unix_output_stream_new (target_fd, FALSE);
+  dataout = g_data_output_stream_new (out_stream);
+
+  if (!_ostree_sysroot_read_boot_loader_configs (self->sysroot, bootversion,
+                                                 &loader_configs,
+                                                 cancellable, error))
+    goto out;
+
+  for (i = 0; i < loader_configs->len; i++)
+    {
+      OstreeBootconfigParser *config = loader_configs->pdata[i];
+      const char *title;
+      const char *options;
+      const char *kernel;
+      const char *initrd;
+      char *line = NULL;
+      char *quoted_title = NULL;
+      char *uuid = NULL;
+      char *quoted_uuid = NULL;
+
+      title = ostree_bootconfig_parser_get (config, "title");
+      if (!title)
+        title = "(Untitled)";
+
+      kernel = ostree_bootconfig_parser_get (config, "linux");
+
+      quoted_title = g_shell_quote (title);
+      uuid = g_strdup_printf ("ostree-%u-%s", (guint)i, grub2_boot_device_id);
+      quoted_uuid = g_shell_quote (uuid);
+      line = g_strdup_printf ("menuentry %s --class gnu-linux --class gnu --class os --unrestricted %s {\n", quoted_title, quoted_uuid);
+      g_free (quoted_title);
+      g_free (quoted_uuid);
+
+      if (!g_data_output_stream_put_string (dataout, line, cancellable, error))
+        goto out;
+
+      /* Hardcoded sections */
+      if (!g_data_output_stream_put_string (dataout, hardcoded_video, cancellable, error))
+        goto out;
+      if (!g_data_output_stream_put_string (dataout, hardcoded_insmods, cancellable, error))
+        goto out;
+      /* Bit extracted from the helper shell script library */
+      if (!g_data_output_stream_put_string (dataout, grub2_prepare_root_cache, cancellable, error))
+        goto out;
+      if (!g_data_output_stream_put_string (dataout, "\n", cancellable, error))
+        goto out;
+      
+      if (!kernel)
+        {
+          g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                       "No \"linux\" key in bootloader config");
+          goto out;
+        }
+      if (!g_data_output_stream_put_string (dataout, "linux16 ", cancellable, error))
+        goto out;
+      if (!g_data_output_stream_put_string (dataout, kernel, cancellable, error))
+        goto out;
+
+      options = ostree_bootconfig_parser_get (config, "options");
+      if (options)
+        {
+          if (!g_data_output_stream_put_string (dataout, " ", cancellable, error))
+            goto out;
+          if (!g_data_output_stream_put_string (dataout, options, cancellable, error))
+            goto out;
+        }
+      if (!g_data_output_stream_put_byte (dataout, '\n', cancellable, error))
+        goto out;
+
+      initrd = ostree_bootconfig_parser_get (config, "initrd");
+      if (initrd)
+        {
+          if (!g_data_output_stream_put_string (dataout, "initrd16 ", cancellable, error))
+            goto out;
+          if (!g_data_output_stream_put_string (dataout, initrd, cancellable, error))
+            goto out;
+          if (!g_data_output_stream_put_byte (dataout, '\n', cancellable, error))
+            goto out;
+        }
+
+      if (!g_data_output_stream_put_string (dataout, "}\n", cancellable, error))
+        goto out;
+    }
+
+  if (!g_data_output_stream_put_string (dataout, "EOF\n", cancellable, error))
+    goto out;
+
+  if (!g_output_stream_flush ((GOutputStream*)dataout, cancellable, error))
+    goto out;
+
+  ret = TRUE;
+ out:
+  return ret;
+}
+
+static gboolean
+_ostree_bootloader_grub2_write_config (OstreeBootloader      *bootloader,
+                                       int                    bootversion,
+                                       GCancellable          *cancellable,
+                                       GError               **error)
+{
+  OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (bootloader);
+  gboolean ret = FALSE;
+  gs_unref_object GFile *new_config_path = NULL;
+  gs_unref_object GSSubprocessContext *procctx = NULL;
+  gs_unref_object GSSubprocess *proc = NULL;
+  gs_strfreev char **child_env = g_get_environ ();
+  gs_free char *bootversion_str = g_strdup_printf ("%u", (guint)bootversion);
+
+  new_config_path = ot_gfile_resolve_path_printf (self->sysroot->path, "boot/loader.%d/grub.cfg",
+                                                  bootversion);
+
+  procctx = gs_subprocess_context_newv ("grub2-mkconfig", "-o",
+                                        gs_file_get_path_cached (new_config_path),
+                                        NULL);
+  child_env = g_environ_setenv (child_env, "_OSTREE_GRUB2_BOOTVERSION", bootversion_str, TRUE);
+  gs_subprocess_context_set_environment (procctx, child_env);
+  gs_subprocess_context_set_stdout_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_NULL);
+  if (g_getenv ("OSTREE_DEBUG_GRUB2"))
+    gs_subprocess_context_set_stderr_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_INHERIT);
+  else
+    gs_subprocess_context_set_stderr_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_NULL);
+
+  /* In the current Fedora grub2 package, this script doesn't even try
+     to be atomic; it just does:
+
+cat ${grub_cfg}.new > ${grub_cfg}
+rm -f ${grub_cfg}.new
+
+     Upstream is fixed though.
+  */
+  proc = gs_subprocess_new (procctx, cancellable, error);
+  if (!proc)
+    goto out;
+
+  if (!gs_subprocess_wait_sync_check (proc, cancellable, error))
+    goto out;
+
+  /* Now let's fdatasync() for the new file */
+  if (!gs_file_sync_data (new_config_path, cancellable, error))
+    goto out;
+  
+  ret = TRUE;
+ out:
+  return ret;
+}
+
+static gboolean
+_ostree_bootloader_grub2_is_atomic (OstreeBootloader      *bootloader) 
+{
+  return TRUE;
+}
+
+static void
+_ostree_bootloader_grub2_finalize (GObject *object)
+{
+  OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (object);
+
+  g_clear_object (&self->sysroot);
+  g_clear_object (&self->config_path_bios);
+
+  G_OBJECT_CLASS (_ostree_bootloader_grub2_parent_class)->finalize (object);
+}
+
+void
+_ostree_bootloader_grub2_init (OstreeBootloaderGrub2 *self)
+{
+}
+
+static void
+_ostree_bootloader_grub2_bootloader_iface_init (OstreeBootloaderInterface *iface)
+{
+  iface->query = _ostree_bootloader_grub2_query;
+  iface->get_name = _ostree_bootloader_grub2_get_name;
+  iface->write_config = _ostree_bootloader_grub2_write_config;
+  iface->is_atomic = _ostree_bootloader_grub2_is_atomic;
+}
+
+void
+_ostree_bootloader_grub2_class_init (OstreeBootloaderGrub2Class *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->finalize = _ostree_bootloader_grub2_finalize;
+}
+
+OstreeBootloaderGrub2 *
+_ostree_bootloader_grub2_new (OstreeSysroot *sysroot)
+{
+  OstreeBootloaderGrub2 *self = g_object_new (OSTREE_TYPE_BOOTLOADER_GRUB2, NULL);
+  self->sysroot = g_object_ref (sysroot);
+  self->config_path_bios = g_file_resolve_relative_path (self->sysroot->path, "boot/grub2/grub.cfg");
+  return self;
+}
diff --git a/src/libostree/ostree-bootloader-grub2.h b/src/libostree/ostree-bootloader-grub2.h
new file mode 100644
index 00000000..334ad49b
--- /dev/null
+++ b/src/libostree/ostree-bootloader-grub2.h
@@ -0,0 +1,40 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+#include "ostree-bootloader.h"
+
+G_BEGIN_DECLS
+
+#define OSTREE_TYPE_BOOTLOADER_GRUB2 (_ostree_bootloader_grub2_get_type ())
+#define OSTREE_BOOTLOADER_GRUB2(inst) (G_TYPE_CHECK_INSTANCE_CAST ((inst), OSTREE_TYPE_BOOTLOADER_GRUB2, OstreeBootloaderGrub2))
+#define OSTREE_IS_BOOTLOADER_GRUB2(inst) (G_TYPE_CHECK_INSTANCE_TYPE ((inst), OSTREE_TYPE_BOOTLOADER_GRUB2))
+
+typedef struct _OstreeBootloaderGrub2 OstreeBootloaderGrub2;
+
+GType _ostree_bootloader_grub2_get_type (void) G_GNUC_CONST;
+
+OstreeBootloaderGrub2 * _ostree_bootloader_grub2_new (OstreeSysroot *sysroot);
+
+gboolean _ostree_bootloader_grub2_generate_config (OstreeBootloaderGrub2 *self, int bootversion, int target_fd, GCancellable *cancellable, GError **error);
+
+G_END_DECLS
+
diff --git a/src/libostree/ostree-bootloader.c b/src/libostree/ostree-bootloader.c
index 5cb7c5ea..37219999 100644
--- a/src/libostree/ostree-bootloader.c
+++ b/src/libostree/ostree-bootloader.c
@@ -61,3 +61,14 @@ _ostree_bootloader_write_config (OstreeBootloader  *self,
   return OSTREE_BOOTLOADER_GET_IFACE (self)->write_config (self, bootversion, 
                                                        cancellable, error);
 }
+
+gboolean
+_ostree_bootloader_is_atomic (OstreeBootloader  *self)
+{
+  g_return_val_if_fail (OSTREE_IS_BOOTLOADER (self), FALSE);
+
+  if (OSTREE_BOOTLOADER_GET_IFACE (self)->is_atomic)
+    return OSTREE_BOOTLOADER_GET_IFACE (self)->is_atomic (self);
+  else
+    return TRUE;
+}
diff --git a/src/libostree/ostree-bootloader.h b/src/libostree/ostree-bootloader.h
index 0d07fdba..a84ce6ba 100644
--- a/src/libostree/ostree-bootloader.h
+++ b/src/libostree/ostree-bootloader.h
@@ -43,6 +43,7 @@ struct _OstreeBootloaderInterface
                                                    int            bootversion,
                                                    GCancellable  *cancellable,
                                                    GError       **error);
+  gboolean             (* is_atomic)              (OstreeBootloader  *self);
 };
 
 GType _ostree_bootloader_get_type (void) G_GNUC_CONST;
@@ -56,5 +57,7 @@ gboolean _ostree_bootloader_write_config (OstreeBootloader  *self,
                                           GCancellable  *cancellable,
                                           GError       **error);
 
+gboolean _ostree_bootloader_is_atomic (OstreeBootloader  *self);
+
 G_END_DECLS
 
diff --git a/src/libostree/ostree-cmdprivate.c b/src/libostree/ostree-cmdprivate.c
new file mode 100644
index 00000000..3d6a1941
--- /dev/null
+++ b/src/libostree/ostree-cmdprivate.c
@@ -0,0 +1,52 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "ostree-cmdprivate.h"
+#include "ostree-sysroot.h"
+#include "ostree-bootloader-grub2.h"
+
+#include "otutil.h"
+
+static gboolean 
+impl_ostree_generate_grub2_config (OstreeSysroot *sysroot, int bootversion, int target_fd, GCancellable *cancellable, GError **error)
+{
+  gs_unref_object OstreeBootloaderGrub2 *grub2 = _ostree_bootloader_grub2_new (sysroot);
+
+  return _ostree_bootloader_grub2_generate_config (grub2, bootversion, target_fd, cancellable, error);
+}
+
+/**
+ * ostree_cmdprivate: (skip)
+ *
+ * Do not call this function; it is used to share private API between
+ * the OSTree commandline and the library.
+ */
+OstreeCmdPrivateVTable *
+ostree_cmd__private__ (void)
+{
+  static OstreeCmdPrivateVTable table = {
+    impl_ostree_generate_grub2_config
+  };
+
+  return &table;
+}
+
diff --git a/src/libostree/ostree-cmdprivate.h b/src/libostree/ostree-cmdprivate.h
new file mode 100644
index 00000000..ac2972a6
--- /dev/null
+++ b/src/libostree/ostree-cmdprivate.h
@@ -0,0 +1,35 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#pragma once
+
+#include "ostree-types.h"
+
+G_BEGIN_DECLS
+
+typedef struct {
+  gboolean (* ostree_generate_grub2_config) (OstreeSysroot *sysroot, int bootversion, int target_fd, GCancellable *cancellable, GError **error);
+} OstreeCmdPrivateVTable;
+
+OstreeCmdPrivateVTable *
+ostree_cmd__private__ (void);
+
+G_END_DECLS
+
diff --git a/src/libostree/ostree-sysroot-deploy.c b/src/libostree/ostree-sysroot-deploy.c
index 905854f1..9934e0f8 100644
--- a/src/libostree/ostree-sysroot-deploy.c
+++ b/src/libostree/ostree-sysroot-deploy.c
@@ -1004,6 +1004,8 @@ get_kernel_from_tree (GFile         *deployroot,
                       GError       **error)
 {
   gboolean ret = FALSE;
+  gs_unref_object GFile *ostree_bootdir
+    = g_file_resolve_relative_path (deployroot, "usr/lib/ostree-boot");
   gs_unref_object GFile *bootdir = g_file_get_child (deployroot, "boot");
   gs_unref_object GFileEnumerator *dir_enum = NULL;
   gs_unref_object GFile *ret_kernel = NULL;
@@ -1011,11 +1013,22 @@ get_kernel_from_tree (GFile         *deployroot,
   gs_free char *kernel_checksum = NULL;
   gs_free char *initramfs_checksum = NULL;
 
-  dir_enum = g_file_enumerate_children (bootdir, OSTREE_GIO_FAST_QUERYINFO,
-                                        G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
-                                        NULL, error);
-  if (!dir_enum)
-    goto out;
+  if (g_file_query_exists (ostree_bootdir, NULL))
+    {
+      dir_enum = g_file_enumerate_children (ostree_bootdir, OSTREE_GIO_FAST_QUERYINFO,
+                                            G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
+                                            NULL, error);
+      if (!dir_enum)
+        goto out;
+    }
+  else
+    {
+      dir_enum = g_file_enumerate_children (bootdir, OSTREE_GIO_FAST_QUERYINFO,
+                                            G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
+                                            NULL, error);
+      if (!dir_enum)
+        goto out;
+    }
 
   while (TRUE)
     {
@@ -1510,6 +1523,7 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
   guint i;
   gboolean requires_new_bootversion = FALSE;
   gboolean found_booted_deployment = FALSE;
+  gboolean bootloader_is_atomic = FALSE;
 
   g_assert (self->loaded);
 
@@ -1578,6 +1592,8 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
           g_prefix_error (error, "Swapping current bootlinks: ");
           goto out;
         }
+      
+      bootloader_is_atomic = TRUE;
     }
   else
     {
@@ -1615,11 +1631,17 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
       g_debug ("Using bootloader: %s", bootloader ?
                g_type_name (G_TYPE_FROM_INSTANCE (bootloader)) : "(none)");
 
-      if (bootloader && !_ostree_bootloader_write_config (bootloader, new_bootversion,
-                                                          cancellable, error))
+      if (bootloader)
+        bootloader_is_atomic = _ostree_bootloader_is_atomic (bootloader);
+
+      if (bootloader)
         {
-          g_prefix_error (error, "Bootloader write config: ");
-          goto out;
+          if (!_ostree_bootloader_write_config (bootloader, new_bootversion,
+                                                cancellable, error))
+            {
+              g_prefix_error (error, "Bootloader write config: ");
+              goto out;
+            }
         }
 
       if (!full_system_sync (cancellable, error))
@@ -1627,7 +1649,7 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
           g_prefix_error (error, "Full sync: ");
           goto out;
         }
-
+      
       if (!swap_bootloader (self, self->bootversion, new_bootversion,
                             cancellable, error))
         {
@@ -1637,7 +1659,8 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
     }
 
   gs_log_structured_print_id_v (OSTREE_DEPLOYMENT_COMPLETE_ID,
-                                "Transaction complete; bootconfig swap: %s deployment count change: %i)",
+                                "%s; bootconfig swap: %s deployment count change: %i",
+                                (bootloader_is_atomic ? "Transaction complete" : "Bootloader updated"),
                                 requires_new_bootversion ? "yes" : "no",
                                 new_deployments->len - self->deployments->len);
 
diff --git a/src/libostree/ostree-sysroot.c b/src/libostree/ostree-sysroot.c
index c88c6d42..160fc078 100644
--- a/src/libostree/ostree-sysroot.c
+++ b/src/libostree/ostree-sysroot.c
@@ -26,6 +26,7 @@
 #include "ostree-sysroot-private.h"
 #include "ostree-bootloader-uboot.h"
 #include "ostree-bootloader-syslinux.h"
+#include "ostree-bootloader-grub2.h"
 
 static gboolean
 find_booted_deployment (OstreeSysroot       *self,
@@ -853,11 +854,16 @@ _ostree_sysroot_query_bootloader (OstreeSysroot *self)
 {
   OstreeBootloaderSyslinux *syslinux;
   OstreeBootloaderUboot    *uboot;
+  OstreeBootloaderGrub2    *grub2;
 
   syslinux = _ostree_bootloader_syslinux_new (self);
   if (_ostree_bootloader_query ((OstreeBootloader*)syslinux))
     return (OstreeBootloader*) (syslinux);
 
+  grub2 = _ostree_bootloader_grub2_new (self);
+  if (_ostree_bootloader_query ((OstreeBootloader*)grub2))
+    return (OstreeBootloader*) (grub2);
+
   uboot = _ostree_bootloader_uboot_new (self);
   if (_ostree_bootloader_query ((OstreeBootloader*)uboot))
     return (OstreeBootloader*) (uboot);
diff --git a/src/ostree/ot-admin-builtin-instutil.c b/src/ostree/ot-admin-builtin-instutil.c
index a0a29d28..7a17dd3b 100644
--- a/src/ostree/ot-admin-builtin-instutil.c
+++ b/src/ostree/ot-admin-builtin-instutil.c
@@ -40,6 +40,7 @@ static OstreeAdminInstUtilCommand admin_instutil_subcommands[] = {
   { "selinux-ensure-labeled", ot_admin_instutil_builtin_selinux_ensure_labeled },
 #endif
   { "set-kargs", ot_admin_instutil_builtin_set_kargs },
+  { "grub2-generate", ot_admin_instutil_builtin_grub2_generate },
   { NULL, NULL }
 };
 
diff --git a/src/ostree/ot-admin-instutil-builtin-grub2-generate.c b/src/ostree/ot-admin-instutil-builtin-grub2-generate.c
new file mode 100644
index 00000000..0b00cf97
--- /dev/null
+++ b/src/ostree/ot-admin-instutil-builtin-grub2-generate.c
@@ -0,0 +1,84 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include <string.h>
+#include <glib-unix.h>
+
+#include "ot-admin-instutil-builtins.h"
+#include "ostree-cmdprivate.h"
+
+#include "otutil.h"
+
+static GOptionEntry options[] = {
+  { NULL }
+};
+
+gboolean
+ot_admin_instutil_builtin_grub2_generate (int argc, char **argv, OstreeSysroot *sysroot, GCancellable *cancellable, GError **error)
+{
+  gboolean ret = FALSE;
+  guint bootversion;
+  gs_unref_object GFile *subpath = NULL;
+  gs_unref_object OstreeSePolicy *sepolicy = NULL;
+  gs_unref_ptrarray GPtrArray *deployments = NULL;
+  GOptionContext *context = NULL;
+  gs_unref_object GFile *deployment_path = NULL;
+
+  context = g_option_context_new ("BOOTVERSION - generate GRUB2 configuration from given BLS entries");
+
+  g_option_context_add_main_entries (context, options, NULL);
+
+  if (!g_option_context_parse (context, &argc, &argv, error))
+    goto out;
+
+  if (argc >= 2)
+    {
+      bootversion = (guint) g_ascii_strtoull (argv[1], NULL, 10);
+      if (!(bootversion == 0 || bootversion == 1))
+        {
+          g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                       "Invalid bootversion: %u", bootversion);
+      goto out;
+        }
+    }
+  else 
+    {
+      const char *bootversion_env = g_getenv ("_OSTREE_GRUB2_BOOTVERSION");
+      if (bootversion_env)
+        bootversion = g_ascii_strtoull (bootversion_env, NULL, 10);
+      else
+        bootversion = ostree_sysroot_get_bootversion (sysroot);
+      g_assert (bootversion == 0 || bootversion == 1);
+    }
+
+  if (!ostree_sysroot_load (sysroot, cancellable, error))
+    goto out;
+
+  if (!ostree_cmd__private__()->ostree_generate_grub2_config (sysroot, bootversion, 1, cancellable, error))
+    goto out;
+
+  ret = TRUE;
+ out:
+  if (context)
+    g_option_context_free (context);
+  return ret;
+}
diff --git a/src/ostree/ot-admin-instutil-builtins.h b/src/ostree/ot-admin-instutil-builtins.h
index b079ddea..5442eb52 100644
--- a/src/ostree/ot-admin-instutil-builtins.h
+++ b/src/ostree/ot-admin-instutil-builtins.h
@@ -26,6 +26,7 @@ G_BEGIN_DECLS
 
 gboolean ot_admin_instutil_builtin_selinux_ensure_labeled (int argc, char **argv, OstreeSysroot *sysroot, GCancellable *cancellable, GError **error);
 gboolean ot_admin_instutil_builtin_set_kargs (int argc, char **argv, OstreeSysroot *sysroot, GCancellable *cancellable, GError **error);
+gboolean ot_admin_instutil_builtin_grub2_generate (int argc, char **argv, OstreeSysroot *sysroot, GCancellable *cancellable, GError **error);
 
 G_END_DECLS
 
diff --git a/tests/test-admin-deploy-grub2.sh b/tests/test-admin-deploy-grub2.sh
new file mode 100755
index 00000000..d07a263a
--- /dev/null
+++ b/tests/test-admin-deploy-grub2.sh
@@ -0,0 +1,30 @@
+#!/bin/bash
+#
+# Copyright (C) 2011,2014 Colin Walters <walters@verbum.org>
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the
+# Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+# Boston, MA 02111-1307, USA.
+
+set -e
+
+. $(dirname $0)/libtest.sh
+
+echo "1..1"
+
+setup_os_repository "archive-z2" "grub2"
+
+echo "ok setup"
+
+. $(dirname $0)/admin-test.sh