diff --git a/Docker Images/quartz/use xxd in docker.md b/Docker Images/quartz/use xxd in docker.md
index 0c5d09f..1d97699 100644
--- a/Docker Images/quartz/use xxd in docker.md	
+++ b/Docker Images/quartz/use xxd in docker.md	
@@ -1,7 +1,10 @@
 ```bash
+# on host
 docker run --rm -it alpine:latest sh
 
+# in container
 apk add xxd openssl
 
-echo PDS_PLC_ROTATION_KEY_K256_PRIVATE_KEY_HEX: $(openssl ecparam --name secp256k1 --genkey --noout --outform DER | tail --bytes=+8 | head --bytes=32 | xxd --plain --cols 32)
+# everything after this is one command
+echo PDS_PLC_ROTATION_KEY_K256_PRIVATE_KEY_HEX: $(openssl ecparam --name secp256k1 --genkey --noout --outform DER | tail -c +8 | head -c 32 | xxd --plain --cols 32)
 ```
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