diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..4e93949
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+MacOSX10.13.sdk.tar.xz
+plugin-build/
diff --git a/Dockerfile b/Dockerfile
index bcbde9e..c2ac6ac 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,16 +1,24 @@
-# TODO upgrade to recent Ubuntu version
-FROM ubuntu:16.04
+FROM ubuntu:20.04
 ENV LANG C.UTF-8
 
 # User to build toolchains and plugins
 RUN groupadd -g 1000 build
 RUN useradd --create-home --uid 1000 --gid 1000 --shell /bin/bash build
 
-USER build
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends make
+
 WORKDIR /home/build
 
-RUN make toolchain-linux
-RUN make toolchain-windows
-RUN make toolchain-mac
+COPY Makefile /home/build/Makefile
+
+# Install dependencies for building toolchains and plugins
+RUN make dep-ubuntu
+
+USER build
+COPY MacOSX10.13.sdk.tar.xz /home/build/MacOSX10.13.sdk.tar.xz
+
+RUN make toolchain-all
 
-# TODO untested
\ No newline at end of file
+RUN rm /home/build/MacOSX10.13.sdk.tar.xz
+RUN rm /home/build/build.log
diff --git a/Makefile b/Makefile
index b569f15..19e8274 100644
--- a/Makefile
+++ b/Makefile
@@ -57,7 +57,7 @@ $(toolchain-mac):
 	#cd $@/build/llvm-10.0.1.src/build && make install
 
 	# Build osxcross
-	cp MacOSX10.13.sdk.tar.bz2 $@/tarballs/
+	cp MacOSX10.13.sdk.tar.* $@/tarballs/
 	cd $@ && UNATTENDED=1 TARGET_DIR="$(LOCAL_DIR)/osxcross" ./build.sh
 	rm -rf osxcross
 
@@ -132,8 +132,8 @@ plugin-build-clean:
 
 
 dep-ubuntu:
-	sudo apt-get update
-	sudo apt-get install -y --no-install-recommends \
+	apt-get update
+	apt-get install -y --no-install-recommends \
 		ca-certificates \
 		git \
 		build-essential \
@@ -160,7 +160,11 @@ dep-ubuntu:
 		libxml2-dev \
 		libssl-dev \
 		texinfo \
-		help2man
+		help2man \
+		clang \
+		libz-dev \
+		rsync
+	rm -rf /var/lib/apt/lists/*
 
 
 dep-arch-linux:
@@ -175,4 +179,12 @@ docker-build:
 
 
 docker-run:
-	docker run --rm -it rack-plugin-toolchain:1
+	mkdir -p $(PLUGIN_BUILD_DIR)
+	docker run --rm -it \
+		-v $(PLUGIN_DIR):/home/build/plugin-src \
+		-v $(PWD)/$(PLUGIN_BUILD_DIR):/home/build/$(PLUGIN_BUILD_DIR) \
+		-e PLUGIN_DIR=plugin-src \
+		rack-plugin-toolchain:1 \
+		/bin/bash \
+		-c "$(MAKE) plugin-build $(MFLAGS)"
+
diff --git a/README.md b/README.md
index 5029c02..4ef1f95 100644
--- a/README.md
+++ b/README.md
@@ -1,38 +1,44 @@
 
 Build Rack plugins for Mac, Windows, and Linux with a single command on any Linux distro.
-Coming soon: Use Docker to build on Mac, Windows, or Linux.
 
+## General prerequisites
 
-## Building
-
-Clone this repository in a path without spaces, or the Makefile will break.
+**IMPORTANT:** Clone this repository in a path without spaces, or the Makefile will break.
 
 Obtain `MacOSX10.13.sdk.tar.bz2` using the method at https://github.com/tpoechtrager/osxcross#packaging-the-sdk, and place it in the root of this repository.
-This must be done on a computer with Mac 10.13.
+This must be done on a computer with macOS 10.13.
+
+Place `MacOSX10.13.sdk.tar.bz2` in root directory of this repository.
+
+## Local toolchain build
 
 Build toolchains for each platform.
 ```
-make toolchain-linux
-make toolchain-windows
-make toolchain-mac
+make toolchain-all
 ```
 Each toolchain will take around an hour to build, requiring network access and about 15 GB free disk space.
 The final disk space after building is about 1.6 GB.
 
-Download the latest Rack SDK.
+Execute plugin build.
 ```
-make rack-sdk
+make plugin-build -j 8 PLUGIN_DIR=...
 ```
 
-## Building plugins
+Build artifacts will be located in `plugin-build` directory.
 
-Build plugin package for all platforms.
+## Docker-based toolchain build
+
+Build Docker image with toolchains for each platform.
 ```
-make plugin-build PLUGIN_DIR=...
+make docker-build
 ```
 
-This places packages in `plugin-build/`.
+Execute plugin build in Docker container.
+```
+make docker-run -j 8 PLUGIN_DIR=...
+```
 
+Build artifacts will be located in `plugin-build` directory.
 
 ## Acknowledgments