+# Check for Docker.
+if [ -f "${root}/.dockerenv" ] || [ -f "${root}/.dockerinit" ] || \
+ grep -qF /docker/ "${root}/proc/self/cgroup" 2>/dev/null; then
+ echo docker
+fi
+
+# Check for OCI.
+if [ -e "${root}/proc/1/environ" ] &&
+ cat "${root}/proc/1/environ" | tr '\000' '\n' | grep -Eiq '^container=oci'; then
+ echo oci
+fi
+
+# Check for CRI-O.
+if [ -e "${root}/proc/1/environ" ] &&
+ cat "${root}/proc/1/environ" | tr '\000' '\n' | grep -Eiq '^container=crio'; then
+ echo crio
+fi
+
+# Check for Podman.
+if [ -e "${root}/proc/1/environ" ] &&
+ cat "${root}/proc/1/environ" | tr '\000' '\n' | grep -Eiq '^container=podman'; then
+ echo podman
+elif grep -qF /libpod- "${root}/proc/self/cgroup" 2>/dev/null; then
+ echo podman
+fi
+