diff --git a/test/.env b/test/.env
index 4318443d..2c0fbef5 100644
--- a/test/.env
+++ b/test/.env
@@ -9,6 +9,11 @@ logdir=$(readlink -f "$testdir/.log")
 envdir="$HOME/.infix-test-venv"
 qeneth="$testdir/qeneth/qeneth"
 
+build_ps1()
+{
+    echo "\e[1m\$(date \"+%H:%M:%S\") \h$1\e[0m:\W # "
+}
+
 #
 # Figure out available container runner
 #
diff --git a/test/env b/test/env
index 06268372..48cae343 100755
--- a/test/env
+++ b/test/env
@@ -160,7 +160,7 @@ if [ "$containerize" ]; then
 	 --env PYTHONHASHSEED=${PYTHONHASHSEED:-$(shuf -i 0-$(((1 << 32) - 1)) -n 1)} \
 	 --env VIRTUAL_ENV_DISABLE_PROMPT=yes \
 	 --env PROMPT_DIRTRIM="$ixdir" \
-	 --env PS1='\e[1m$(date "+%H:%M:%S") \h\e[0m:\W # ' \
+	 --env PS1="$(build_ps1)" \
 	 --expose 9001-9010 --publish-all \
 	 --hostname "$(name)" \
 	 --name "$(name)" \
diff --git a/test/nsenter b/test/nsenter
new file mode 100755
index 00000000..6557a5c5
--- /dev/null
+++ b/test/nsenter
@@ -0,0 +1,24 @@
+#!/bin/sh
+
+set -e
+
+testdir=$(dirname "$(readlink -f "$0")")
+. "$testdir/.env"
+
+lower=$1
+shift
+[ $# -gt 0 ] || set sh
+
+for pid in $(pgrep -fx "sleep infinity"); do
+    ifidxs=$(nsenter -t $pid -U -n ip -j link show | \
+    		 jq '.[] | select(has("link_netnsid")) | .link_index')
+    for ifidx in $ifidxs; do
+	ifname=$(ip -j link show | jq -r ".[] | select(.ifindex == $ifidx) | .ifname")
+	if [ "$ifname" = "$lower" ]; then
+	    exec nsenter -t $pid -U -n env PS1="$(build_ps1 "(netns:$ifname)")" "$@"
+	fi
+    done
+done
+
+echo Found no namespace with interface stacked on $lower >&2
+exit 1