diff --git a/.dockerignore b/.dockerignore
index fb78ae7..e7bf1da 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -4,3 +4,5 @@ dist/*
 go.work
 go.work.sum
 modd.*conf
+test-initrd*
+test-initrd/**/*
diff --git a/Dockerfile b/Dockerfile
index 9385f34..2abca56 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -9,7 +9,9 @@ run go test ./...
 run go build -o /go/bin/init -trimpath .
 
 # ------------------------------------------------------------------------
-from alpine:3.18.4
+from alpine:3.18.4 as initrd
+
+run apk add --no-cache xz
 
 workdir /layer
 run wget -O- https://dl-cdn.alpinelinux.org/alpine/v3.18/releases/x86_64/alpine-minirootfs-3.18.4-x86_64.tar.gz |tar zxv
@@ -22,4 +24,9 @@ copy --from=build /go/bin/init .
 # check viability
 run chroot /layer /init hello
 
-entrypoint ["sh","-c","find |cpio -H newc -o |base64"]
+run find |cpio -H newc -o >/initrd
+
+# ------------------------------------------------------------------------
+from alpine:3.18.4
+copy --from=initrd /initrd /
+entrypoint ["base64","/initrd"]
diff --git a/modd.test.conf b/modd.test.conf
index d4fb958..9e7154c 100644
--- a/modd.test.conf
+++ b/modd.test.conf
@@ -3,7 +3,8 @@ modd.test.conf {}
 dist/initrd dist/cpiocat dist/testconf test-initrd/**/* {
     prep: dist/testconf test-initrd/config.yaml
     prep: cp -f dist/initrd test-initrd.cpio
-    prep: cd test-initrd && ../dist/cpiocat <../dist/initrd >../test-initrd.cpio *
-    prep: if cpio -t -F test-initrd.cpio 2>&1 |grep bytes.of.junk; then echo "bad cpio archive"; exit 1; fi
+    prep: cd test-initrd && cat ../dist/initrd | ../dist/cpiocat * |lz4 -l9v >../test-initrd.cpio.new
+    prep: mv test-initrd.cpio.new test-initrd.cpio
+    prep: if lz4cat test-initrd.cpio | cpio -t 2>&1 |grep bytes.of.junk; then echo "bad cpio archive"; exit 1; fi
     prep: kill $(<qemu.pid)
 }