diff --git a/.vscode/cspell.json b/.vscode/cspell.json
index ef956cced460..2b7e12e65b80 100644
--- a/.vscode/cspell.json
+++ b/.vscode/cspell.json
@@ -152,6 +152,7 @@
     "deserialization",
     "docfx",
     "dotenv",
+    "dpkg",
     "DWORD",
     "eastus",
     "eckey",
@@ -494,7 +495,8 @@
         "nlocals",
         "kwonlyargcount",
         "dcid",
-        "startf"
+        "startf",
+        "dpkg"
       ]
     }
   ],
diff --git a/sdk/eventhub/azure-eventhub/stress/Dockerfile b/sdk/eventhub/azure-eventhub/stress/Dockerfile
index 05c55e17da28..de521bb3bf45 100644
--- a/sdk/eventhub/azure-eventhub/stress/Dockerfile
+++ b/sdk/eventhub/azure-eventhub/stress/Dockerfile
@@ -1,6 +1,7 @@
-# syntax=docker/dockerfile:1
-
-FROM python:3.8-slim-buster
+# internal users should provide MCR registry to build via 'docker build . --build-arg REGISTRY="mcr.microsoft.com/mirror/docker/library/"'
+# public OSS users should simply leave this argument blank or ignore its presence entirely
+ARG REGISTRY=""
+FROM ${REGISTRY}python:3.8-slim-buster
 
 WORKDIR /app
 
diff --git a/sdk/identity/azure-identity/tests/azure-functions/Dockerfile b/sdk/identity/azure-identity/tests/azure-functions/Dockerfile
index 04c4001ea683..28ec1cf4df62 100644
--- a/sdk/identity/azure-identity/tests/azure-functions/Dockerfile
+++ b/sdk/identity/azure-identity/tests/azure-functions/Dockerfile
@@ -3,7 +3,13 @@
 # Licensed under the MIT License.
 # ------------------------------------
 # docker can't tell when the repo has changed and will therefore cache this layer
-FROM alpine/git as repo
+
+# internal users should provide MCR registry to build via 'docker build . --build-arg REGISTRY="mcr.microsoft.com/mirror/docker/library/"'
+# public OSS users should simply leave this argument blank or ignore its presence entirely
+ARG REGISTRY=""
+
+FROM ${REGISTRY}alpine:3.14 as repo
+RUN apk --no-cache add git
 RUN git clone https://github.com/Azure/azure-sdk-for-python --single-branch --depth 1 /azure-sdk-for-python
 
 
diff --git a/sdk/identity/azure-identity/tests/managed-identity-live/Dockerfile b/sdk/identity/azure-identity/tests/managed-identity-live/Dockerfile
index 13631a3010db..69daa0fd76ac 100644
--- a/sdk/identity/azure-identity/tests/managed-identity-live/Dockerfile
+++ b/sdk/identity/azure-identity/tests/managed-identity-live/Dockerfile
@@ -2,14 +2,18 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 # ------------------------------------
+
+# internal users should provide MCR registry to build via 'docker build . --build-arg REGISTRY="mcr.microsoft.com/mirror/docker/library/"'
+# public OSS users should simply leave this argument blank or ignore its presence entirely
+ARG REGISTRY=""
 ARG PYTHON_VERSION=3.9
 
 # docker can't tell when the repo has changed and will therefore cache this layer
-FROM alpine/git as repo
+FROM ${REGISTRY}alpine:3.14 as repo
+RUN apk --no-cache add git
 RUN git clone https://github.com/Azure/azure-sdk-for-python --single-branch --depth 1 /azure-sdk-for-python
 
-
-FROM python:${PYTHON_VERSION}-slim
+FROM ${REGISTRY}python:${PYTHON_VERSION}-slim
 
 COPY --from=repo /azure-sdk-for-python/sdk/identity /sdk/identity
 COPY --from=repo /azure-sdk-for-python/sdk/core/azure-core /sdk/core/azure-core
diff --git a/sdk/servicebus/azure-servicebus/stress/Dockerfile b/sdk/servicebus/azure-servicebus/stress/Dockerfile
index 2fd60803a44b..f13d54baff04 100644
--- a/sdk/servicebus/azure-servicebus/stress/Dockerfile
+++ b/sdk/servicebus/azure-servicebus/stress/Dockerfile
@@ -1,6 +1,7 @@
-# syntax=docker/dockerfile:1
-
-FROM python:3.8-slim-buster
+# internal users should provide MCR registry to build via 'docker build . --build-arg REGISTRY="mcr.microsoft.com/mirror/docker/library/"'
+# public OSS users should simply leave this argument blank or ignore its presence entirely
+ARG REGISTRY=""
+FROM ${REGISTRY}python:3.8-slim-buster
 
 WORKDIR /app
 
diff --git a/tools/Dockerfile b/tools/Dockerfile
index 27a3832ee341..aed1c4eba7ed 100644
--- a/tools/Dockerfile
+++ b/tools/Dockerfile
@@ -1,5 +1,9 @@
-FROM ubuntu
-MAINTAINER zikalino
+# internal users should provide MCR registry to build via 'docker build . --build-arg REGISTRY="mcr.microsoft.com/mirror/docker/library/"'
+# public OSS users should simply leave this argument blank or ignore its presence entirely
+ARG REGISTRY=""
+FROM ${REGISTRY}ubuntu:20.04
+LABEL MAINTAINER=zikalino \
+      MAINTAINER=scbedd
 
 RUN apt-get update
 RUN apt-get install -y git curl gnupg vim python3 python3-pip git software-properties-common apt-transport-https wget python3-venv nodejs npm libunwind-dev