[OE-core] [PATCH 1/2] rootfs.py: remove update-alternatives correctly

[Mikko Ylinen]

With "read-only-rootfs" in IMAGE_FEATURES, packages in ROOTFS_RO_UNNEEDED
are removed when building the rootfs. The list of packages to remove is
passed to the package manager and the list is sorted so that
update-alternatives provider is the last entry. This is with the
assumption that the last entry on the list/command line is removed last.

However, it turns out rpm does not care about "last on the command
line" and update-alternatives provider is removed before other the
packages get to run their %preun scripts for update-alternatives.

This leaves broken alternative symlinks in rootfs.

The fix is to first remove all but update-alternatives provider and
after that update-alternatives provider in its own remove() call.

Signed-off-by: Mikko Ylinen <mikko.ylinen at linux.intel.com>
---
 meta/lib/oe/rootfs.py | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/meta/lib/oe/rootfs.py b/meta/lib/oe/rootfs.py
index 9d4727e..5f62015 100644
--- a/meta/lib/oe/rootfs.py
+++ b/meta/lib/oe/rootfs.py
@@ -261,15 +261,22 @@ class Rootfs(object, metaclass=ABCMeta):
             # Remove components that we don't need if it's a read-only rootfs
             unneeded_pkgs = self.d.getVar("ROOTFS_RO_UNNEEDED").split()
             pkgs_installed = image_list_installed_packages(self.d)
-            # Make sure update-alternatives is last on the command line, so
-            # that it is removed last. This makes sure that its database is
-            # available while uninstalling packages, allowing alternative
-            # symlinks of packages to be uninstalled to be managed correctly.
+            # Make sure update-alternatives is removed last. This is
+            # because its database has to available while uninstalling
+            # other packages, allowing alternative symlinks of packages
+            # to be uninstalled or to be managed correctly otherwise.
             provider = self.d.getVar("VIRTUAL-RUNTIME_update-alternatives")
             pkgs_to_remove = sorted([pkg for pkg in pkgs_installed if pkg in unneeded_pkgs], key=lambda x: x == provider)
 
+            # update-alternatives provider is removed in its own remove()
+            # call because all package managers do not guarantee the packages
+            # are removed in the order they given in the list (which is
+            # passed to the command line). The sorting done earlier is
+            # utilized to implement the 2-stage removal.
+            if len(pkgs_to_remove) > 1:
+                self.pm.remove(pkgs_to_remove[:-1], False)
             if len(pkgs_to_remove) > 0:
-                self.pm.remove(pkgs_to_remove, False)
+                self.pm.remove([pkgs_to_remove[-1]], False)
 
         if delayed_postinsts:
             self._save_postinsts()
-- 
2.1.4