diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index af80dfb72..4a5d9f57a 100644
--- a/.devcontainer/Dockerfile
+++ b/.devcontainer/Dockerfile
@@ -1,12 +1,19 @@
-FROM ubuntu:24.04 AS spython-base
+FROM ubuntu:24.04
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+WORKDIR /workspace
+
 RUN export DEBIAN_FRONTEND=noninteractive
 RUN apt-get update
 RUN apt-get install -y --no-install-recommends git gh
 RUN apt-get install -y --no-install-recommends less
 RUN apt-get install -y --no-install-recommends python3
-RUN apt-get install -y --no-install-recommends python3.12-venv python3-pip
+RUN apt-get install -y --no-install-recommends python3.12-venv
+RUN apt-get install -y --no-install-recommends python3-pip
 RUN apt-get install -y --no-install-recommends build-essential
-RUN apt-get install -y --no-install-recommends ruby ruby-dev
+RUN apt-get install -y --no-install-recommends ruby
+RUN apt-get install -y --no-install-recommends ruby-dev
 RUN apt-get install -y --no-install-recommends bundler
 RUN apt-get install -y --no-install-recommends nodejs
 RUN apt-get install -y --no-install-recommends npm
@@ -14,4 +21,6 @@ RUN apt-get install -y --no-install-recommends ditaa
 RUN apt-get install -y --no-install-recommends libyaml-dev
 RUN apt-get clean autoclean
 RUN apt-get autoremove -y
-RUN rm -rf /var/lib/{apt, dpkg, cache, log}
+RUN rm -rf /var/lib/{apt,dpkg,cache,log}/*
+
+WORKDIR /workspace
diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index 73c2dfd92..c79c6e138 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -26,6 +26,8 @@ jobs:
     needs: check_date
     if: ${{ needs.check_date.outputs.should_run != 'false' }}
     runs-on: ubuntu-latest
+    env:
+      SINGULARITY: 1
     steps:
       - name: Clone Github Repo Action
         uses: actions/checkout@v4
diff --git a/.github/workflows/regress.yml b/.github/workflows/regress.yml
index da6f5b15e..5d7b86a93 100644
--- a/.github/workflows/regress.yml
+++ b/.github/workflows/regress.yml
@@ -13,6 +13,8 @@ jobs:
       - uses: pre-commit/action@v3.0.1
   regress-smoke:
     runs-on: ubuntu-latest
+    env:
+      SINGULARITY: 1
     steps:
       - name: Clone Github Repo Action
         uses: actions/checkout@v4
@@ -45,6 +47,7 @@ jobs:
     env:
       MANUAL_NAME: isa
       VERSIONS: all
+      SINGULARITY: 1
     steps:
       - name: Clone Github Repo Action
         uses: actions/checkout@v4
@@ -75,6 +78,7 @@ jobs:
     env:
       EXT: B
       VERSION: latest
+      SINGULARITY: 1
     steps:
       - name: Clone Github Repo Action
         uses: actions/checkout@v4
@@ -102,6 +106,8 @@ jobs:
   regress-gen-certificate:
     runs-on: ubuntu-latest
     needs: regress-smoke
+    env:
+      SINGULARITY: 1
     steps:
       - name: Clone Github Repo Action
         uses: actions/checkout@v4
@@ -129,6 +135,8 @@ jobs:
   regress-gen-profile:
     runs-on: ubuntu-latest
     needs: regress-smoke
+    env:
+      SINGULARITY: 1
     steps:
       - name: Clone Github Repo Action
         uses: actions/checkout@v4
diff --git a/.gitignore b/.gitignore
index e82076dd8..ddd1aa6a7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@
 .stamps
 .venv
 .asciidoctor
+.container-type
 diag-ditaa-*
 arch/manual/isa/**/riscv-isa-manual
 gen
diff --git a/bin/setup b/bin/setup
index 9ea0591f5..934c8033a 100755
--- a/bin/setup
+++ b/bin/setup
@@ -6,66 +6,146 @@ cd $ROOT
 
 CONTAINER_TAG=`cat ${ROOT}/bin/.container-tag`
 
+# Supported container types:
+#
+# = devcontainer
+#
+# When devcontainer is used, all commands run "natively" (no container prefix), because it's assumed
+# that the command itself is already in the container context
+#
+# = docker
+#
+# A docker container. All commands on the host (using ./do or ./bin/*) are run in the context of a Docker image.
+#
+# = singularity
+#
+# An apptainer/singularity container. All commands on the host (using ./do or ./bin/*) are run in the context of an Apptainer/Singularity image.
+#
+#
+# ALL THREE CONTAINERS ARE IDENTICAL. Which one you use is a preference of your setup and installed
+# software.
+
+
+# get the container type
+#
+# use, in priority order:
+#  1. devcontainer, if DEVCONTAINER_ENV is set in the enviornment
+#  2. the type stored in .container-type
+#  3. Docker, if DOCKER is set in the enviornment
+#  4. Singularity, if SINGULARITY is set in the enviornment
+#  5. The choice made by the user, which will be cached in .container-type
+if [ -v DEVCONTAINER_ENV ]; then
+CONTAINER_TYPE=devcontainer
+elif [ -f ${ROOT}/.container-type ]; then
+CONTAINER_TYPE=`cat ${ROOT}/.container-type`
+elif [ -v DOCKER ]; then
+CONTAINER_TYPE=docker
+elif [ -v SINGULARITY ]; then
+CONTAINER_TYPE=singularity
+else
+  echo -e "UDB tools run in a container. Both Docker and Singularity/Apptainer are supported.\\n\\n1. Docker\\n2. Singularity\\n"
+  while true; do
+    echo "Which would you like to use? (1/2) "
+    read ans
+    case $ans in
+        [1]* ) CONTAINER_TYPE=docker; break;;
+        [2]* ) CONTAINER_TYPE=singularity; break;;
+        * ) echo -e "\\nPlease answer 1 or 2.";;
+    esac
+  done
+fi
+
+if [ "${CONTAINER_TYPE}" != "docker" -a "${CONTAINER_TYPE}" != "singularity" ]; then
+  echo "BAD CONTAINER TYPE: ${CONTAINER_TYPE}"
+fi
+
+if [ ! -f ${ROOT}/.container-type ]; then
+  echo ${CONTAINER_TYPE} > ${ROOT}/.container-type
+fi
+
+print_env() {
+    if [ "${CONTAINER_TYPE}" == "docker" ]; then
+        echo "Using Docker environment"
+    else
+        echo "Using Singularity environment"
+    fi
+}
+
 if [ -v GITHUB_ACTIONS ]; then
-  echo "ACTIONS"
-  CONTAINER_PATH=${ROOT}/.singularity/image.sif
-  HOME_PATH=${GITHUB_WORKSPACE}
-  HOME_OPT="--home ${ROOT}/.home"
-  SINGULARITY_CACHE=--disable-cache
+    echo "ACTIONS"
+    CONTAINER_PATH=${ROOT}/.singularity/image.sif
+    HOME_PATH=${GITHUB_WORKSPACE}
+    HOME_OPT="--home ${ROOT}/.home"
+    SINGULARITY_CACHE=--disable-cache
+elif [ "${CONTAINER_TYPE}" == "docker" ]; then
+    print_env
+    if ! docker images riscvintl/udb:${CONTAINER_TAG} | grep -q udb ; then
+        # TODO: pull the image if it can be found
+        echo "Building Docker image..."
+        docker build -t riscvintl/udb:${CONTAINER_TAG} -f .devcontainer/Dockerfile .
+    fi
+    if [ -t 1 -a -t 0 ]; then
+      DOCKER_BASE="docker run -it -v $(ROOT):$(ROOT) -w $(ROOT) riscvintl/udb:${CONTAINER_TAG}"
+    else
+      DOCKER_BASE="docker run -v $(ROOT):$(ROOT) -w $(ROOT) riscvintl/udb:${CONTAINER_TAG}"
+    fi
+    RUN="${DOCKER_BASE}"
 else
-  CONTAINER_PATH=${ROOT}/.singularity/image-$CONTAINER_TAG.sif
-  HOME_PATH=${HOME}
-  HOME_OPT="--bind ${ROOT}/.home:${HOME_PATH} --bind /local/mnt/workspace/.vscode-server:/local/mnt/workspace/.vscode-server"
-  SINGULARITY_CACHE=
+    print_env
+    CONTAINER_PATH=${ROOT}/.singularity/image-$CONTAINER_TAG.sif
+    HOME_PATH=${HOME}
+    HOME_OPT="--bind ${ROOT}/.home:${HOME_PATH}"
+    SINGULARITY_CACHE=
+    if [ ! -f ${CONTAINER_PATH} ]; then
+      echo "Fetching container..."
+      if [ ! -d "${ROOT}/.singularity" ]; then
+        mkdir -p ${ROOT}/.singularity
+      fi
+      singularity pull ${SINGULARITY_CACHE} ${CONTAINER_PATH} oras://docker.io/riscvintl/spec-generator:$CONTAINER_TAG
+    fi
 fi
 
 if [ -f $ROOT/.git ]; then
-  # if this is a worktree, need to add the parent git repo in, too
-  GIT_PATH=`git rev-parse --git-common-dir | tr -d '\n' | xargs dirname`
-  HOME_OPT="${HOME_OPT} --bind ${GIT_PATH}:${GIT_PATH}"
+    # if this is a worktree, need to add the parent git repo in, too
+    GIT_PATH=`git rev-parse --git-common-dir | tr -d '\n' | xargs dirname`
+    HOME_OPT="${HOME_OPT} --bind ${GIT_PATH}:${GIT_PATH}"
 fi
 
 if [ -v DEVCONTAINER_ENV ]; then
-  RUN=""
+    RUN=""
+elif [ "${CONTAINER_TYPE}" == "docker" ]; then
+    RUN="${DOCKER_BASE}"
 else
-  RUN="singularity run  ${HOME_OPT} ${CONTAINER_PATH} "
+    RUN="singularity run ${HOME_OPT} ${CONTAINER_PATH}"
 fi
 
 if [ ! -d $ROOT/.home ]; then
-  mkdir $ROOT/.home
-fi
-
-if [ ! -v DEVCONTAINER_ENV ]; then
-  if [ ! -f ${CONTAINER_PATH} ]; then
-  echo "Fetching container..."
-    if [ ! -d "${ROOT}/.singularity" ]; then
-      mkdir -p ${ROOT}/.singularity
-    fi
-    singularity pull ${SINGULARITY_CACHE} ${CONTAINER_PATH} oras://docker.io/riscvintl/spec-generator:$CONTAINER_TAG
-  fi
+    mkdir $ROOT/.home
 fi
 
 if [ ! -f $ROOT/.bundle/config ]; then
-  OLDDIR=$PWD
-  cd $ROOT
-  ${RUN} bundle config set --local path ${ROOT}/.home/.gems
-  ${RUN} bundle config set --local cache_path ${ROOT}/.home/.cache
-  cd $OLDDIR
+    OLDDIR=$PWD
+    cd $ROOT
+    ${RUN} bundle config set --local path ${ROOT}/.home/.gems
+    ${RUN} bundle config set --local cache_path ${ROOT}/.home/.cache
+    cd $OLDDIR
 fi
 
 if [ ! -d $ROOT/.home/.gems ]; then
-  OLDDIR=$PWD
-  cd $ROOT
-  ${RUN} bundle install
-  cd $OLDDIR
+    OLDDIR=$PWD
+    cd $ROOT
+    ${RUN} bundle install
+    cd $OLDDIR
 fi
 
 if [ ! -d $ROOT/.home/.venv ]; then
-  ${RUN} /usr/bin/python3 -m venv ${ROOT}/.home/.venv
+    ${RUN} /usr/bin/python3 -m venv ${ROOT}/.home/.venv
 fi
+
 source ${ROOT}/.home/.venv/bin/activate
+
 if [ ! -f ${ROOT}/.home/.venv/bin/pre-commit ]; then
-  ${RUN} ${ROOT}/.home/.venv/bin/pip install -r requirements.txt
+    ${RUN} ${ROOT}/.home/.venv/bin/pip install -r requirements.txt
 fi
 
 # if [ ! -f $ROOT/ext/riscv-opcodes/README.md ]; then
@@ -73,37 +153,47 @@ fi
 # fi
 
 if [[ ! -z "$DEVELOPMENT" && $DEVELOPMENT -eq 1 ]]; then
-  if [ ! -d "${ROOT}/.home/.yard/gem_index"]; then
-    ${RUN} bundle exec --gemfile ${ROOT}/Gemfile yard config --gem-install-yri
-    ${RUN} bundle exec --gemfile ${ROOT}/Gemfile yard gems
-    touch ${ROOT}/.stamps/dev_gems
-  fi
+    if [ ! -d "${ROOT}/.home/.yard/gem_index"]; then
+        ${RUN} bundle exec --gemfile ${ROOT}/Gemfile yard config --gem-install-yri
+        ${RUN} bundle exec --gemfile ${ROOT}/Gemfile yard gems
+        touch ${ROOT}/.stamps/dev_gems
+    fi
 fi
 
 if [ ! -d ${ROOT}/node_modules ]; then
-  ${RUN} npm i
+    ${RUN} npm i
 fi
 
 if [ -v DEVCONTAINER_ENV ]; then
-  BUNDLE="bundle"
-  RUBY="bundle exec ruby"
-  RAKE="bundle exec rake"
-  NPM="npm"
-  NPX="npx"
-  NODE="node"
-  PYTHON="${ROOT}/.home/.venv/bin/python3"
-  PIP="${ROOT}/.home/.venv/bin/pip"
-  BASH="bash"
+    BUNDLE="bundle"
+    RUBY="bundle exec ruby"
+    RAKE="bundle exec rake"
+    NPM="npm"
+    NPX="npx"
+    NODE="node"
+    PYTHON="${ROOT}/.home/.venv/bin/python3"
+    PIP="${ROOT}/.home/.venv/bin/pip"
+    BASH="bash"
+elif [ "${CONTAINER_TYPE}" == "docker" ]; then
+    BUNDLE="${DOCKER_BASE} bundle"
+    RUBY="${DOCKER_BASE} bundle exec ruby"
+    RAKE="${DOCKER_BASE} bundle exec rake"
+    NPM="${DOCKER_BASE} npm"
+    NPX="${DOCKER_BASE} npx"
+    NODE="${DOCKER_BASE} node"
+    PYTHON="${DOCKER_BASE} ${ROOT}/.home/.venv/bin/python3"
+    PIP="${DOCKER_BASE} ${ROOT}/.home/.venv/bin/pip"
+    BASH="${DOCKER_BASE} bash"
 else
-  BUNDLE="singularity run ${HOME_OPT} ${CONTAINER_PATH} bundle"
-  RUBY="singularity run ${HOME_OPT} ${CONTAINER_PATH} bundle exec ruby"
-  RAKE="singularity run ${HOME_OPT} ${CONTAINER_PATH} bundle exec rake"
-  NPM="singularity run ${HOME_OPT} ${CONTAINER_PATH} npm"
-  NPX="singularity run ${HOME_OPT} ${CONTAINER_PATH} npx"
-  NODE="singularity run ${HOME_OPT} ${CONTAINER_PATH} node"
-  PYTHON="singularity run ${HOME_OPT} ${CONTAINER_PATH} ${ROOT}/.home/.venv/bin/python3"
-  PIP="singularity run ${HOME_OPT} ${CONTAINER_PATH} ${ROOT}/.home/.venv/bin/pip"
-  BASH="singularity run ${HOME_OPT} ${CONTAINER_PATH} bash"
+    BUNDLE="singularity run ${HOME_OPT} ${CONTAINER_PATH} bundle"
+    RUBY="singularity run ${HOME_OPT} ${CONTAINER_PATH} bundle exec ruby"
+    RAKE="singularity run ${HOME_OPT} ${CONTAINER_PATH} bundle exec rake"
+    NPM="singularity run ${HOME_OPT} ${CONTAINER_PATH} npm"
+    NPX="singularity run ${HOME_OPT} ${CONTAINER_PATH} npx"
+    NODE="singularity run ${HOME_OPT} ${CONTAINER_PATH} node"
+    PYTHON="singularity run ${HOME_OPT} ${CONTAINER_PATH} ${ROOT}/.home/.venv/bin/python3"
+    PIP="singularity run ${HOME_OPT} ${CONTAINER_PATH} ${ROOT}/.home/.venv/bin/pip"
+    BASH="singularity run ${HOME_OPT} ${CONTAINER_PATH} bash"
 fi
 
 if [ ! -f $ROOT/.git/hooks/pre-commit ]; then
@@ -125,7 +215,7 @@ if [ -x "\$INSTALL_PYTHON" ]; then
 elif command -v pre-commit > /dev/null; then
     exec pre-commit "\${ARGS[@]}"
 else
-    echo '`pre-commit` not found.  Did you forget to activate your virtualenv?' 1>&2
+    echo '\`pre-commit\` not found.  Did you forget to activate your virtualenv?' 1>&2
     exit 1
 fi
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