[Libguestfs] [p2v PATCH 2/4] make-disk: restrict kernel update bug work-around

[Laszlo Ersek]

Commit 2764abefaa14 ("make-disk: Don't upgrade the kernel to avoid kernel
command line bug", 2022-03-24) replaced the "--update" option of
virt-builder with an open-coded DNF update command, excluding the kernel
packages from the update.

Albeit a justified workaround, it is a bit too broad: it breaks on all
guest OS images that don't have DNF, such as old RHEL, Debian and Ubuntu,
etc.  (In a subsequent patch, I'm going to refactor the Debian/Ubuntu
branch, and for testing that, I first need eliminate the open-coded DNF
command.)  Refine the workaround as follows:

- I've tested Fedora 33 and Fedora 37; they work without the workaround
  (they are not yet, and no longer, affected by the bug, respectively).

- I've tested Fedora 34 and 36, they are affected.  They need the
  workaround.

- Fedora 35 is also broken, per
  <https://bugzilla.redhat.com/show_bug.cgi?id=1945835#c24>.

- RHEL-9.0 and RHEL-9.1 *seem* to work fine without the workaround (that
  is, with commit 2764abefaa14 reverted).  However, that's deceptive: in
  my testing, the original "--update" option does not bring in any new
  kernel packages, so even if the bug is still there, it is not triggered.
  Because RHEL-9 is based on Fedora 34, which is affected, assume that
  RHEL-9 is affected too.

Signed-off-by: Laszlo Ersek <lersek at redhat.com>
---
 virt-p2v-make-disk.in | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/virt-p2v-make-disk.in b/virt-p2v-make-disk.in
index 865a92847f8b..44ff0b45ac7a 100644
--- a/virt-p2v-make-disk.in
+++ b/virt-p2v-make-disk.in
@@ -48,6 +48,7 @@ eval set -- "$TEMP"
 output=
 upload=
 verbose=
+declare -a update_option=(--update)
 declare -a passthru
 
 usage ()
@@ -184,6 +185,19 @@ EOF
           --upload $tmpdir/p2v.conf:/etc/dracut.conf.d/
           --run $tmpdir/post-install
         "
+        # Fedora 34 through 36, and presumably RHEL-9 (based on Fedora 34)
+        # suffer from a bug where a kernel image installation via libguestfs
+        # pollutes the just installed kernel's commandline in the boot loader
+        # config file.  Irrelevant and bogus parameters from the appliance
+        # kernel's /proc/cmdline are copied over.  This prevents the root
+        # filesystem from being mounted.  Refer to
+        # <https://bugzilla.redhat.com/show_bug.cgi?id=1945835#c24> and/or
+        # commit 2764abefaa14.
+        case "$osversion" in
+            fedora-34|fedora-35|fedora-36|rhel-9.*)
+                update_option=(--run-command 'dnf -y update --exclude=kernel\*')
+                ;;
+        esac
         ;;
     debian-*|ubuntu-*)
         depsfile="$datadir/dependencies.debian"
@@ -246,7 +260,7 @@ virt-builder "$osversion"                                       \
     $preinstall_args                                            \
     --hostname p2v.local                                        \
     --run-command 'hostname p2v.local'                          \
-    --run-command 'dnf -y update --exclude=kernel\*'            \
+    "${update_option[@]}"                                       \
     --install "$install"                                        \
     --root-password password:p2v                                \
     --upload "$datadir"/issue:/etc/issue                        \