test: pass /dev/kvm's gid to docker numerically

Group names resolved on the host do not exist inside the container,
so the "kvm" fallback broke --group-add on hosts where getent found
no kvm group. stat the device instead; the numeric gid is all that
matters and /dev/kvm is already known to exist at this point.

1 files changed, 4 insertions, 4 deletions

diff --git a/test b/test
index de6eaf6..7ccfc8f 100755
--- a/test
+++ b/test
@@ -69,10 +69,10 @@ if [ -n "$needs_kvm" ]; then
         echo "          sudo usermod -aG kvm $(id -un)" >&2
         exit 3
     fi
-    # Pass through the host's kvm gid so the container user (mapped to
-    # host uid:gid) can actually open /dev/kvm.
-    kvm_gid=$(getent group kvm | awk -F: '{print $3}')
-    kvm_args="--device /dev/kvm --group-add ${kvm_gid:-kvm}"
+    # Pass through /dev/kvm's owning gid (numeric - group names from the
+    # host don't exist inside the container) so the container user
+    # (mapped to host uid:gid) can actually open it.
+    kvm_args="--device /dev/kvm --group-add $(stat -c %g /dev/kvm)"
 fi
 
 # Forward Ctrl-C cleanly, run as the host user so files in .tools/ stay