diff --git a/docker/README b/docker/README
index bf03a4c0a4..d824ff8337 100644
--- a/docker/README
+++ b/docker/README
@@ -1,14 +1,27 @@
-These scripts are useful for testing on different versions of Linux
-assuming that you are running a version of Linux that has docker
-available.
+These scripts are useful for building and testing on different versions of
+Linux.
+
+ORC is currently supported on:
+* CentOS 6, 7, and 8
+* Debian 8, 9, and 10
+* Ubuntu 14, 16, and 18
 
 To test against all of the Linux OSes against Apache's master branch:
-1. ./run-all.sh apache master
+1. cd docker
+2. ./run-all.sh apache master
+
+The scripts are:
+1. run-all.sh *owner* *branch* - test the given owner's branch on all OSes
+2. run-one.sh *owner* *branch* *os* - test the owner's branch on one OS
+3. reinit.sh - rebuild all of the base images without the image cache
 
-To run the docker scripts:
-1. cd $os
+A base image for each OS is built using:
+1. cd docker/$os
 2. docker build -t orc-$os .
-3. docker run orc-$os
+
+If you want to test the download version on $os (assuming you are in the ORC
+top level directory):
+1. docker run -v`pwd`:/root/orc orc-$os
 
 To clean up docker:
 1. docker container prune
diff --git a/docker/centos6/Dockerfile b/docker/centos6/Dockerfile
index 6fffbb7b7e..5763adeb01 100644
--- a/docker/centos6/Dockerfile
+++ b/docker/centos6/Dockerfile
@@ -62,8 +62,10 @@ RUN cd snappy-1.1.3 && \
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \ 
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake -DSNAPPY_HOME=/usr/local -DPROTOBUF_HOME=/usr/local ../orc && \
+    make package test-out
diff --git a/docker/centos7/Dockerfile b/docker/centos7/Dockerfile
index 2074fde1af..d343e2d349 100644
--- a/docker/centos7/Dockerfile
+++ b/docker/centos7/Dockerfile
@@ -54,8 +54,10 @@ RUN cd snappy-1.1.3 && \
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \ 
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake -DSNAPPY_HOME=/usr/local ../orc && \
+    make package test-out
diff --git a/docker/centos8/Dockerfile b/docker/centos8/Dockerfile
index 4a6d2c6d78..6621d82171 100644
--- a/docker/centos8/Dockerfile
+++ b/docker/centos8/Dockerfile
@@ -46,8 +46,10 @@ WORKDIR /root
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \ 
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake ../orc && \
+    make package test-out
diff --git a/docker/debian10/Dockerfile b/docker/debian10/Dockerfile
index fb73d5b2a5..8574f3cfc5 100644
--- a/docker/debian10/Dockerfile
+++ b/docker/debian10/Dockerfile
@@ -36,8 +36,10 @@ WORKDIR /root
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake ../orc && \
+    make package test-out
diff --git a/docker/debian8/Dockerfile b/docker/debian8/Dockerfile
index 24145bac44..1f5ca2b72d 100644
--- a/docker/debian8/Dockerfile
+++ b/docker/debian8/Dockerfile
@@ -53,8 +53,10 @@ RUN cd snappy-1.1.3 && \
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake -DSNAPPY_HOME=/usr/local ../orc && \
+    make package test-out
diff --git a/docker/debian9/Dockerfile b/docker/debian9/Dockerfile
index 06a5a50a61..04312aef09 100644
--- a/docker/debian9/Dockerfile
+++ b/docker/debian9/Dockerfile
@@ -36,8 +36,10 @@ WORKDIR /root
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake ../orc && \
+    make package test-out
diff --git a/docker/ubuntu14/Dockerfile b/docker/ubuntu14/Dockerfile
index 008207f627..8e66fe1727 100644
--- a/docker/ubuntu14/Dockerfile
+++ b/docker/ubuntu14/Dockerfile
@@ -51,8 +51,10 @@ RUN cd snappy-1.1.3 && \
 
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \ 
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake -DSNAPPY_HOME=/usr/local ../orc && \
+    make package test-out
diff --git a/docker/ubuntu16-clang5/Dockerfile b/docker/ubuntu16-clang5/Dockerfile
index f3178631f6..67b95a32ad 100644
--- a/docker/ubuntu16-clang5/Dockerfile
+++ b/docker/ubuntu16-clang5/Dockerfile
@@ -42,8 +42,10 @@ ENV CXX=clang++-5.0
 WORKDIR /root
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake ../orc && \
+    make package test-out
diff --git a/docker/ubuntu16/Dockerfile b/docker/ubuntu16/Dockerfile
index 5eca40b423..800e29e336 100644
--- a/docker/ubuntu16/Dockerfile
+++ b/docker/ubuntu16/Dockerfile
@@ -36,8 +36,10 @@ RUN apt-get install -y \
 WORKDIR /root
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake ../orc && \
+    make package test-out
diff --git a/docker/ubuntu18/Dockerfile b/docker/ubuntu18/Dockerfile
index 650fa2043c..6fdda39218 100644
--- a/docker/ubuntu18/Dockerfile
+++ b/docker/ubuntu18/Dockerfile
@@ -38,8 +38,10 @@ RUN update-java-alternatives --set java-1.8.0-openjdk-amd64
 WORKDIR /root
 VOLUME /root/.m2/repository
 
-CMD git clone https://github.com/apache/orc.git -b master && \
-  mkdir orc/build && \
-  cd orc/build && \
-  cmake .. && \
-  make package test-out
+CMD if [ ! -d orc ]; then \
+      git clone https://github.com/apache/orc.git -b master; \
+    fi && \
+    mkdir build && \
+    cd build && \
+    cmake ../orc && \
+    make package test-out
\ No newline at end of file