compose: Add boot-location: modules

And this (for now at least) completes the epic journey of the
"where's the kernel"?  With this it's found solely in
`/usr/lib/modules/$kver`.

There are a few reasons to do this; most prominent is that
it avoids duplicating the content as the locations may have
different SELinux labels.

Closes: #1773
Approved by: jlebon

docs/manual/treefile.md

@@ -26,9 +26,15 @@ It supports the following parameters:
  * `selinux`: boolean, optional: Defaults to `true`.  If `false`, then
    no SELinux labeling will be performed on the server side.
 
- * `boot-location` (or `boot_location`): string, optional: If specified, this value
-    must be "new".  Historically rpm-ostree supported multiple kernel locations;
-    this is no longer the case.
+ * `boot-location` (or `boot_location`): string, optional:
+    There are 2 possible values:
+    * "new": A misnomer, this value is no longer "new".  Kernel data
+      goes in `/usr/lib/ostree-boot` in addition to `/usr/lib/modules`.
+      This is the default; use it if you have a need to care about
+      upgrading from very old versions of libostree.
+    * "modules": Kernel data goes just in `/usr/lib/modules`.  Use
+      this for new systems, and systems that don't need to be upgraded
+      from very old libostree versions.
 
  * `etc-group-members`: Array of strings, optional: Unix groups in this
    list will be stored in `/etc/group` instead of `/usr/lib/group`.  Use

rust/src/treefile.rs

@@ -520,6 +520,8 @@ fn whitespace_split_packages(pkgs: &[String]) -> Vec<String> {
 enum BootLocation {
     #[serde(rename = "new")]
     New,
+    #[serde(rename = "modules")]
+    Modules,
 }
 
 impl Default for BootLocation {

src/libpriv/rpmostree-postprocess.c

@@ -50,7 +50,8 @@
 #include "rpmostree-rust.h"
 
 typedef enum {
-  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW
+  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW,
+  RPMOSTREE_POSTPROCESS_BOOT_LOCATION_MODULES,
 } RpmOstreePostprocessBootLocation;
 
 /* The "unified_core_mode" flag controls whether or not we use rofiles-fuse,
@@ -363,7 +364,11 @@ process_kernel_and_initramfs (int            rootfs_dfd,
     return FALSE;
   if (boot_location_str != NULL)
     {
-      if (!g_str_equal (boot_location_str, "new"))
+      if (g_str_equal (boot_location_str, "new"))
+        boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_NEW;
+      else if (g_str_equal (boot_location_str, "modules"))
+        boot_location = RPMOSTREE_POSTPROCESS_BOOT_LOCATION_MODULES;
+      else
         return glnx_throw (error, "Invalid boot location '%s'", boot_location_str);
     }
 
@@ -439,9 +444,12 @@ process_kernel_and_initramfs (int            rootfs_dfd,
   /* We always tell rpmostree_finalize_kernel() to skip /boot, since we'll do a
    * full hardlink pass if needed after that for the kernel + bootloader data.
    */
+  RpmOstreeFinalizeKernelDestination fin_dest =
+    (boot_location == RPMOSTREE_POSTPROCESS_BOOT_LOCATION_MODULES) ?
+    RPMOSTREE_FINALIZE_KERNEL_USRLIB_MODULES :
+    RPMOSTREE_FINALIZE_KERNEL_USRLIB_OSTREEBOOT;
   if (!rpmostree_finalize_kernel (rootfs_dfd, bootdir, kver, kernel_path,
-                                  &initramfs_tmpf,
-                                  RPMOSTREE_FINALIZE_KERNEL_USRLIB_OSTREEBOOT,
+                                  &initramfs_tmpf, fin_dest,
                                   cancellable, error))
     return FALSE;
 

tests/compose-tests/test-boot-location-modules.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+set -xeuo pipefail
+
+dn=$(cd $(dirname $0) && pwd)
+. ${dn}/libcomposetest.sh
+
+prepare_compose_test "bootlocation-modules"
+pysetjsonmember "boot_location" '"modules"'
+runcompose
+echo "ok compose"
+
+# Nothing in /boot (but it should exist)
+ostree --repo=${repobuild} ls -R ${treeref} /boot > bootls.txt
+cat >bootls-expected.txt <<EOF
+d00755 0 0      0 /boot
+EOF
+diff -u bootls{-expected,}.txt
+# Verify /usr/lib/ostree-boot
+ostree --repo=${repobuild} ls -R ${treeref} /usr/lib/ostree-boot > bootls.txt
+assert_not_file_has_content bootls.txt vmlinuz-
+assert_not_file_has_content bootls.txt initramfs-
+# And use the kver to find the kernel in /usr/lib/modules
+ostree --repo=${repobuild} ls -R ${treeref} /usr/lib/modules > modules-lsr.txt
+assert_file_has_content modules-lsr.txt '/vmlinuz$'
+assert_file_has_content modules-lsr.txt '/initramfs.img$'
+echo "ok boot location modules"