diff --git a/skills/ci/rhdh-base-images/SKILL.md b/skills/ci/rhdh-base-images/SKILL.md
index d446ba0b..1deb5d92 100644
--- a/skills/ci/rhdh-base-images/SKILL.md
+++ b/skills/ci/rhdh-base-images/SKILL.md
@@ -72,6 +72,13 @@ until that path is migrated.
   that same latest released 4.y (for example `/rhocp/4.21/` → `/rhocp/4.22/`).
   Leave `ocp-tools` URLs unchanged. Do not rewrite when the life cycle fetch
   fails.
+- When the RPM Containerfile uses `dnf`/`microdnf install --installroot`
+  (operator empty rootfs), regenerate the lockfile with
+  `rpm-lockfile-prototype --bare` so the full closure (glibc, coreutils, bash)
+  is locked. Do not pass `-f`; that loads the UBI rpmdb and omits those
+  packages. Layered installs onto the base image still use `-f`. If the solve
+  fails (`nothing provides`, `conflicting requests`), restore
+  `rpms.lock.yaml` / `rpms.in.yaml` and do not push.
 - On RHDH, update Node headers when the builder image changes Node. Then, when
   those checkouts are in scope, pin plugin-catalog
   `build/containerfiles/builder.Containerfile` FROM to the same UBI Node
diff --git a/skills/ci/rhdh-base-images/references/repos.md b/skills/ci/rhdh-base-images/references/repos.md
index b530b51a..55ba87c6 100644
--- a/skills/ci/rhdh-base-images/references/repos.md
+++ b/skills/ci/rhdh-base-images/references/repos.md
@@ -22,7 +22,7 @@
 - Clone: `https://github.com/redhat-developer/rhdh-operator.git`
 - Branches: `main`, `release-1.9`, `release-1.10`, …
 - Base images: `.rhdh/docker/Dockerfile`, root `Dockerfile`
-- RPM lock: `.rhdh/docker/Dockerfile` + `rpms.in.yaml` → `rpms.lock.yaml`
+- RPM lock: root `Dockerfile` or `.rhdh/docker/Dockerfile` + `rpms.in.yaml` → `rpms.lock.yaml`. The `rpm-builder` stage uses `--installroot`; regenerate with `rpm-lockfile-prototype --bare` (not `-f`).
 - Workflow reference: `.github/workflows/update-rpm-lockfile.yaml`
 
 ## GitLab rhidp/rhdh-plugin-catalog
diff --git a/skills/ci/rhdh-base-images/scripts/base-images-and-rpms.sh b/skills/ci/rhdh-base-images/scripts/base-images-and-rpms.sh
index bfebaa2f..542f9456 100755
--- a/skills/ci/rhdh-base-images/scripts/base-images-and-rpms.sh
+++ b/skills/ci/rhdh-base-images/scripts/base-images-and-rpms.sh
@@ -540,21 +540,45 @@ bump_catalog_builder_rhocp() {
     bump_rhocp_version_in_file "${catalog_cf}" "${new_ver}"
 }
 
+# Empty --installroot (operator rpm-builder) needs --bare so glibc/coreutils
+# land in the lockfile. Layered installs onto the base image stay on -f.
+containerfile_uses_installroot() {
+    local file="$1"
+    [[ -f "${file}" ]] || return 1
+    grep -qE -- '--installroot' "${file}"
+}
+
+# $1: file to inspect for --installroot
+# $2: Containerfile path passed to -f (relative after cd into the repo)
+# stdout: arguments after the rpm-lockfile-prototype binary.
+rpm_lockfile_prototype_args() {
+    local inspect="$1"
+    local relative="$2"
+    if containerfile_uses_installroot "${inspect}"; then
+        printf '%s\n' "--bare rpms.in.yaml"
+    else
+        printf '%s\n' "-f ${relative} rpms.in.yaml"
+    fi
+}
+
 update_rpm_lockfile() {
     local repo_dir="$1"
     local kind="$2"
     local rpm_tool="$3"
     local branch="$4"
-    local containerfile rpm_err rpm_rc
+    local containerfile rpm_err rpm_rc proto_args
+    local -a proto_cmd=()
     containerfile=$(rpm_containerfile_for "${repo_dir}" "${kind}" "${branch}")
 
     [[ -f "${repo_dir}/${containerfile}" ]] || die "${repo_dir}: missing ${containerfile}"
     [[ -f "${repo_dir}/rpms.in.yaml" ]] || die "${repo_dir}: missing rpms.in.yaml"
 
-    log "RPM lockfile: $(basename "${repo_dir}") using ${containerfile}"
+    proto_args=$(rpm_lockfile_prototype_args "${repo_dir}/${containerfile}" "${containerfile}")
+
+    log "RPM lockfile: $(basename "${repo_dir}") using ${containerfile} (${proto_args})"
     if [[ ${DRY_RUN} -eq 1 ]]; then
         echo "  dry-run: bump OpenShift N-el9-beta URLs in ${repo_dir}/rpms.in.yaml when present"
-        echo "  dry-run: (cd ${repo_dir} && ${rpm_tool} -f ${containerfile} rpms.in.yaml)"
+        echo "  dry-run: (cd ${repo_dir} && ${rpm_tool} ${proto_args})"
         echo "  dry-run: commit and push rpms.in.yaml and rpms.lock.yaml to open base-images PR branch (or chore/automated-update-rpm-lockfile/${branch})"
         return 0
     fi
@@ -564,11 +588,15 @@ update_rpm_lockfile() {
     pushd "${repo_dir}" >/dev/null
     rpm_err=$(mktemp)
     rpm_rc=0
-    "${rpm_tool}" -f "${containerfile}" rpms.in.yaml 2>"${rpm_err}" || rpm_rc=$?
+    read -r -a proto_cmd <<< "${proto_args}"
+    "${rpm_tool}" "${proto_cmd[@]}" 2>"${rpm_err}" || rpm_rc=$?
     filter_rpm_lockfile_source_warnings <"${rpm_err}" >&2
     rm -f "${rpm_err}"
     if [[ ${rpm_rc} -ne 0 ]]; then
         warn "rpm-lockfile-prototype failed for ${repo_dir}; keeping existing rpms.lock.yaml"
+        git checkout -- rpms.lock.yaml rpms.in.yaml 2>/dev/null || true
+        popd >/dev/null
+        return 0
     fi
     commit_push_rpm_lockfile "${branch}"
     popd >/dev/null
diff --git a/skills/ci/rhdh-base-images/workflows/update-base-images.md b/skills/ci/rhdh-base-images/workflows/update-base-images.md
index 32a3421c..15ee8db8 100644
--- a/skills/ci/rhdh-base-images/workflows/update-base-images.md
+++ b/skills/ci/rhdh-base-images/workflows/update-base-images.md
@@ -152,7 +152,10 @@ Matches each repo's GitHub Action, then commits and pushes to the automation PR:
 # capped at the latest released 4.y (4.21-el9-beta 404s once 4.22-el9-beta
 # is the newest released stream still on the mirror). Do not follow
 # unreleased directories such as 4.23-el9-beta or 5.1-el9-beta.
+# Layered install onto the base image:
 rpm-lockfile-prototype -f CONTAINERFILE rpms.in.yaml
+# Empty --installroot (operator rpm-builder): do not pass -f
+rpm-lockfile-prototype --bare rpms.in.yaml
 git add rpms.in.yaml rpms.lock.yaml
 git commit -s -m "chore: update rpms.lock.yaml [skip-build]"
 git push origin <chore/automated-update-base-images-*>   # same PR as base images
@@ -203,6 +206,7 @@ Do not downgrade. If `go.mod` already pins a newer toolchain (for example `go1.2
 - Omitting `registry.redhat.io` login before base image updates.
 - Committing `rpms.lock.yaml` without checking the base image minor (e.g. UBI `9.8`) still matches `rpms.in.yaml` repo URLs.
 - Regenerating `rpms.lock.yaml` while `rpms.in.yaml` still points at a vanished OpenShift `N-el9-beta` directory (hermeto FetchError on `openshift-clients`).
+- Solving an `--installroot` Containerfile with `-f` (image rpmdb). openssl then lands without glibc/coreutils; hermetic `dnf install --installroot` fails with `nothing provides`. Use `--bare`.
 - Bumping `rpms.in.yaml` or catalog `builder.Containerfile` `/rhocp/4.N/` to an unreleased OpenShift stream (`4.23`, `5.1`). Those RPMs are signed with a key UBI 9 microdnf cannot verify. Stay on the latest released 4.y.
 - Treating `rpm-lockfile-prototype` `No sources found for` / "no matching sources" warnings as a failure or remaining risk. The source RPM is often unpublished; the lockfile is still valid.
 - Lowering `go.mod` `toolchain` (or `go`) to match an older UBI Go toolset image. Keep the newer pin.
diff --git a/tests/unit/test_base_images_and_rpms.py b/tests/unit/test_base_images_and_rpms.py
index 2603b890..9e5db452 100644
--- a/tests/unit/test_base_images_and_rpms.py
+++ b/tests/unit/test_base_images_and_rpms.py
@@ -473,6 +473,60 @@ def test_bump_rhocp_version_in_file_rewrites_rhocp_only(self, tmp_path: Path) ->
         assert "/rhocp/4.21/" not in text
         assert "/ocp-tools/4.22/os/" in text
 
+    def test_rpm_lockfile_prototype_args_bare_for_installroot(self, tmp_path: Path) -> None:
+        helpers = (
+            _extract_bash_function(MAIN_SCRIPT, "containerfile_uses_installroot")
+            + "\n"
+            + _extract_bash_function(MAIN_SCRIPT, "rpm_lockfile_prototype_args")
+        )
+        dockerfile = tmp_path / "Dockerfile"
+        dockerfile.write_text(
+            "RUN dnf install --installroot /mnt/rootfs openssl --releasever 10 -y\n",
+            encoding="utf-8",
+        )
+        result = subprocess.run(
+            [
+                "bash",
+                "-c",
+                f'{helpers}\nrpm_lockfile_prototype_args "$1" "$2"',
+                "bash",
+                str(dockerfile),
+                "Dockerfile",
+            ],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        assert result.returncode == 0, result.stderr
+        assert result.stdout.strip() == "--bare rpms.in.yaml"
+
+    def test_rpm_lockfile_prototype_args_layered_uses_containerfile(self, tmp_path: Path) -> None:
+        helpers = (
+            _extract_bash_function(MAIN_SCRIPT, "containerfile_uses_installroot")
+            + "\n"
+            + _extract_bash_function(MAIN_SCRIPT, "rpm_lockfile_prototype_args")
+        )
+        containerfile = tmp_path / "Containerfile"
+        containerfile.write_text(
+            "RUN microdnf install -y tar gzip jq\n",
+            encoding="utf-8",
+        )
+        result = subprocess.run(
+            [
+                "bash",
+                "-c",
+                f'{helpers}\nrpm_lockfile_prototype_args "$1" "$2"',
+                "bash",
+                str(containerfile),
+                "Containerfile",
+            ],
+            capture_output=True,
+            text=True,
+            check=False,
+        )
+        assert result.returncode == 0, result.stderr
+        assert result.stdout.strip() == "-f Containerfile rpms.in.yaml"
+
     def test_skill_covers_openshift_el9_beta_rpm_bump(self) -> None:
         skill = (SKILL_DIR / "SKILL.md").read_text(encoding="utf-8")
         assert "N-el9-beta" in skill
@@ -481,6 +535,10 @@ def test_skill_covers_openshift_el9_beta_rpm_bump(self) -> None:
         script = MAIN_SCRIPT.read_text(encoding="utf-8")
         assert "bump_openshift_rpm_repos" in script
         assert "bump_catalog_builder_rhocp" in script
+        assert "rpm_lockfile_prototype_args" in script
+        assert "--bare rpms.in.yaml" in script
+        assert "keeping existing rpms.lock.yaml" in script
+        assert "rpm-lockfile-prototype --bare" in skill
         unresolved = script.split(
             'warn "plugin-catalog: could not resolve a Node headers version', 1
         )[1][:500]