compose: Support 'boot_location' to facilitate GRUB2

Having content in /boot in OSTree was always ugly, because we ended up
mounting over it in the deployment location at boot.

This was even worse in the anaconda rpmostreepayload code, because of
the juggling of the mount point that needed to take place.

Trying to add a GRUB2 backend to OSTree is what finally forced this
change.  Now, we put kernels (in the tree) by default in *both* /boot
and /usr/lib/ostree-boot.

OSTree itself knows to look in both locations.  Anaconda is going to
just hard require trees with the new location though.

doc/treefile.md

@@ -14,6 +14,14 @@ Treefile
  * `selinux`: boolean, optional: Defaults to `true`.  If `false`, then
    no SELinux labeling will be performed on the server side.
 
+ * `boot_location`: string, optional: Historically, ostree put bootloader data
+    in /boot.  However, this has a few flaws; it gets shadowed at boot time,
+    and also makes dealing with Anaconda installation harder.  There are 3
+    possible values:
+    * "legacy": the default, data goes in /boot
+    * "both": Kernel data in /boot and /usr/lib/ostree-boot
+    * "new": Kernel data in /usr/lib/ostree-boot
+
  * `bootstrap_packages`: Array of strings, mandatory: The `glibc` and
    `nss-altfiles` packages (and ideally nothing else) must be in this
    set; rpm-ostree will modify the `/etc/nsswitch.conf` in the target

src/rpmostree-compose-builtin-tree.c

@@ -945,8 +945,34 @@ rpmostree_compose_builtin_tree (int             argc,
   if (g_strcmp0 (g_getenv ("RPM_OSTREE_BREAK"), "post-yum") == 0)
     goto out;
 
-  if (!rpmostree_postprocess (yumroot, cancellable, error))
-    goto out;
+  {
+    const char *boot_location_str = NULL;
+    RpmOstreePostprocessBootLocation boot_location =
+      RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH;
+
+    if (!object_get_optional_string_member (treefile, "boot_location",
+                                            &boot_location_str, error))
+      goto out;
+
+    if (boot_location_str != NULL)
+      {
+        if (strcmp (boot_location_str, "legacy") == 0)
+          boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_LEGACY;
+        else if (strcmp (boot_location_str, "both") == 0)
+          boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH;
+        else if (strcmp (boot_location_str, "new") == 0)
+          boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW;
+        else
+          {
+            g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                         "Invalid boot location '%s'", boot_location_str);
+            goto out;
+          }
+      }
+
+    if (!rpmostree_postprocess (yumroot, boot_location, cancellable, error))
+      goto out;
+  }
 
   if (json_object_has_member (treefile, "units"))
     units = json_object_get_array_member (treefile, "units");

src/rpmostree-postprocess.c

@@ -725,6 +725,7 @@ replace_nsswitch (GFile         *target_usretc,
 /* Prepare a root filesystem, taking mainly the contents of /usr from yumroot */
 static gboolean 
 create_rootfs_from_yumroot_content (GFile         *targetroot,
+                                    RpmOstreePostprocessBootLocation boot_location,
                                     GFile         *yumroot,
                                     GCancellable  *cancellable,
                                     GError       **error)
@@ -862,9 +863,44 @@ create_rootfs_from_yumroot_content (GFile         *targetroot,
   {
     gs_unref_object GFile *yumroot_boot =
       g_file_get_child (yumroot, "boot");
-
-    if (!move_to_dir (yumroot_boot, targetroot, cancellable, error))
+    gs_unref_object GFile *target_boot =
+      g_file_get_child (targetroot, "boot");
+    gs_unref_object GFile *target_usrlib =
+      g_file_resolve_relative_path (targetroot, "usr/lib");
+    gs_unref_object GFile *target_usrlib_ostree_boot =
+      g_file_resolve_relative_path (target_usrlib, "ostree-boot");
+
+    if (!gs_file_ensure_directory (target_usrlib, TRUE, cancellable, error))
       goto out;
+
+    switch (boot_location)
+      {
+      case RPMOSTREE_POSTPROCESS_BOOT_LOCATION_LEGACY:
+        {
+          g_print ("Using boot location: legacy\n");
+          if (!gs_file_rename (yumroot_boot, target_boot, cancellable, error))
+            goto out;
+        }
+        break;
+      case RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH:
+        {
+          g_print ("Using boot location: both\n");
+          if (!gs_file_rename (yumroot_boot, target_boot, cancellable, error))
+            goto out;
+          /* Hardlink the existing content, only a little ugly as
+           * we'll end up sha256'ing it twice, but oh well. */
+          if (!gs_shutil_cp_al_or_fallback (target_boot, target_usrlib_ostree_boot, cancellable, error))
+            goto out;
+        }
+        break;
+      case RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW:
+        {
+          g_print ("Using boot location: new\n");
+          if (!gs_file_rename (yumroot_boot, target_usrlib_ostree_boot, cancellable, error))
+            goto out;
+        }
+        break;
+      }
   }
 
   /* Also carry along toplevel compat links */
@@ -910,6 +946,7 @@ create_rootfs_from_yumroot_content (GFile         *targetroot,
 
 gboolean
 rpmostree_postprocess (GFile         *rootfs,
+                       RpmOstreePostprocessBootLocation boot_location,
                        GCancellable  *cancellable,
                        GError       **error)
 {
@@ -923,7 +960,7 @@ rpmostree_postprocess (GFile         *rootfs,
   if (!gs_shutil_rm_rf (rootfs_tmp, cancellable, error))
     goto out;
 
-  if (!create_rootfs_from_yumroot_content (rootfs_tmp, rootfs, cancellable, error))
+  if (!create_rootfs_from_yumroot_content (rootfs_tmp, boot_location, rootfs, cancellable, error))
     goto out;
 
   if (!gs_shutil_rm_rf (rootfs, cancellable, error))

src/rpmostree-postprocess.h

@@ -22,8 +22,15 @@
 
 #include <ostree.h>
 
+typedef enum {
+  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_LEGACY,
+  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_BOTH,
+  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW
+} RpmOstreePostprocessBootLocation;
+
 gboolean
 rpmostree_postprocess (GFile         *rootfs,
+                       RpmOstreePostprocessBootLocation boot_style,
                        GCancellable  *cancellable,
                        GError       **error);