diff --git a/.github/workflows/_checks.yml b/.github/workflows/_checks.yml
index 0828919..ea27d07 100644
--- a/.github/workflows/_checks.yml
+++ b/.github/workflows/_checks.yml
@@ -71,6 +71,7 @@ jobs:
       - run: uv python pin 3.12
       - run: just install
       - run: podman --version
+      - run: sh probe_round3.sh
       - run: just test-integration
 
   conformance:
diff --git a/probe_round3.sh b/probe_round3.sh
new file mode 100755
index 0000000..9ee2bec
--- /dev/null
+++ b/probe_round3.sh
@@ -0,0 +1,40 @@
+#!/bin/sh
+# Throwaway probe, round 2. Deleted before merge.
+set -u
+IMG=busybox:1.36
+podman pull -q "$IMG" >/dev/null 2>&1
+
+echo "=== A2. nocopy: WHICH entries land in the volume ==="
+for opt in "" ":nocopy"; do
+  vol="v2$(echo "$opt" | tr -d ':')"
+  podman volume rm -f "$vol" >/dev/null 2>&1; podman volume create "$vol" >/dev/null
+  podman run --rm -v "${vol}:/etc${opt}" "$IMG" true >/dev/null 2>&1
+  printf 'mounted at /etc%-8s -> volume contains: %s\n' "$opt" \
+    "$(podman run --rm -v "${vol}:/mnt" "$IMG" sh -c 'ls -1A /mnt | tr "\n" " "')"
+done
+
+echo
+echo "=== A2. candidate target dirs with content (not needed by the shell) ==="
+podman run --rm "$IMG" sh -c 'for d in /usr/sbin /var/spool/mail /home /root /var/www; do printf "%-18s %s\n" "$d" "$(ls -1A $d 2>/dev/null | wc -l)"; done'
+
+echo
+echo "=== A2. copy-up at /usr/sbin, away from podman's own /etc files ==="
+for opt in "" ":nocopy"; do
+  vol="v3$(echo "$opt" | tr -d ':')"
+  podman volume rm -f "$vol" >/dev/null 2>&1; podman volume create "$vol" >/dev/null
+  seen=$(podman run --rm -v "${vol}:/usr/sbin${opt}" "$IMG" sh -c 'ls -1A /usr/sbin | wc -l' 2>&1)
+  after=$(podman run --rm -v "${vol}:/mnt" "$IMG" sh -c 'ls -1A /mnt | wc -l' 2>&1)
+  printf '  -v vol:/usr/sbin%-8s container sees=%-5s volume afterwards=%s\n' "$opt" "$seen" "$after"
+done
+
+echo
+echo "=== B2. --gpus on 4.9.3: hidden, and does it do anything? ==="
+echo "grep -i gpu over the whole help text:"; podman run --help | grep -i gpu || echo "  (absent from --help)"
+for v in all 1 nonsense ""; do
+  out=$(podman run --rm --gpus "$v" "$IMG" true 2>&1); rc=$?
+  printf '  --gpus %-10s exit=%s %s\n' "'$v'" "$rc" "$(echo "$out" | tr '\n' ' ' | cut -c1-90)"
+done
+echo "does --gpus all add any device? (nvidia entries in /dev):"
+podman run --rm --gpus all "$IMG" sh -c 'ls /dev | grep -ci nvidia'
+echo "man page mention:"; (podman run --help 2>&1; man podman-run 2>/dev/null) | grep -ci gpus
+echo "done."