fix docker image entrypoints (#17105)

Also removes extraneous prompt and ssh handling logic.

7 files changed, 269 insertions, 436 deletions

diff --git a/share/spack/docker/centos-6.dockerfile b/share/spack/docker/centos-6.dockerfile
index 72aa934f99..fe919f3c88 100644
--- a/share/spack/docker/centos-6.dockerfile
+++ b/share/spack/docker/centos-6.dockerfile
@@ -16,46 +16,42 @@ COPY share $SPACK_ROOT/share
 COPY var   $SPACK_ROOT/var
 RUN mkdir -p $SPACK_ROOT/opt/spack
 
-RUN yum update -y                                             \
- && yum install -y epel-release                               \
- && yum update -y                                             \
+RUN ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/docker-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/interactive-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/spack-env
+
+RUN yum update -y \
+ && yum install -y epel-release \
+ && yum update -y \
  && yum --enablerepo epel groupinstall -y "Development Tools" \
- && yum --enablerepo epel install -y                          \
-        curl           findutils gcc-c++    gcc               \
-        gcc-gfortran   git       gnupg2     hostname          \
-        iproute        Lmod      make       patch             \
-        openssh-server python    python-pip tcl               \
-        unzip          which                                  \
- && pip install boto3                                         \
- && rm -rf /var/cache/yum                                     \
+ && yum --enablerepo epel install -y \
+        curl \
+        findutils \
+        gcc-c++ \
+        gcc \
+        gcc-gfortran \
+        git \
+        gnupg2 \
+        hostname \
+        iproute \
+        Lmod \
+        make \
+        patch \
+        python \
+        python-pip \
+        tcl \
+        unzip \
+        which \
+ && pip install boto3 \
+ && rm -rf /var/cache/yum \
  && yum clean all
 
-RUN ( echo ". /usr/share/lmod/lmod/init/bash"                       \
- &&   echo ". \$SPACK_ROOT/share/spack/setup-env.sh"                \
- &&   echo "if [ \"\$CURRENTLY_BUILDING_DOCKER_IMAGE\" '!=' '1' ]"  \
- &&   echo "then"                                                   \
- &&   echo "  . \$SPACK_ROOT/share/spack/spack-completion.bash"     \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/spack.sh                                   \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-ssh.sh\""    \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-ssh.sh             \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-ssh.sh                              \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-prompt.sh\"" \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-prompt.sh          \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-prompt.sh                           \
- && mkdir -p /root/.spack                                           \
- && cp $SPACK_ROOT/share/spack/docker/modules.yaml                  \
-        /root/.spack/modules.yaml                                   \
+RUN mkdir -p /root/.spack \
+ && cp $SPACK_ROOT/share/spack/docker/modules.yaml \
+        /root/.spack/modules.yaml \
  && rm -rf /root/*.* /run/nologin $SPACK_ROOT/.git
 
 # [WORKAROUND]
@@ -66,10 +62,10 @@ RUN [ -f ~/.profile ]                                               \
  || true
 
 WORKDIR /root
-SHELL ["/bin/bash", "-l", "-c"]
+SHELL ["docker-shell"]
 
 # TODO: add a command to Spack that (re)creates the package cache
 RUN spack spec hdf5+mpi
 
 ENTRYPOINT ["/bin/bash", "/opt/spack/share/spack/docker/entrypoint.bash"]
-CMD ["docker-shell"]
+CMD ["interactive-shell"]
diff --git a/share/spack/docker/centos-7.dockerfile b/share/spack/docker/centos-7.dockerfile
index 6aa969fef8..67affa1af9 100644
--- a/share/spack/docker/centos-7.dockerfile
+++ b/share/spack/docker/centos-7.dockerfile
@@ -16,46 +16,42 @@ COPY share $SPACK_ROOT/share
 COPY var   $SPACK_ROOT/var
 RUN mkdir -p $SPACK_ROOT/opt/spack
 
-RUN yum update -y                                             \
- && yum install -y epel-release                               \
- && yum update -y                                             \
+RUN ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/docker-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/interactive-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/spack-env
+
+RUN yum update -y \
+ && yum install -y epel-release \
+ && yum update -y \
  && yum --enablerepo epel groupinstall -y "Development Tools" \
- && yum --enablerepo epel install -y                          \
-        curl           findutils gcc-c++    gcc               \
-        gcc-gfortran   git       gnupg2     hostname          \
-        iproute        Lmod      make       patch             \
-        openssh-server python    python-pip tcl               \
-        unzip          which                                  \
- && pip install boto3                                         \
- && rm -rf /var/cache/yum                                     \
+ && yum --enablerepo epel install -y \
+        curl \
+        findutils \
+        gcc-c++ \
+        gcc \
+        gcc-gfortran \
+        git \
+        gnupg2 \
+        hostname \
+        iproute \
+        Lmod \
+        make \
+        patch \
+        python \
+        python-pip \
+        tcl \
+        unzip \
+        which \
+ && pip install boto3 \
+ && rm -rf /var/cache/yum \
  && yum clean all
 
-RUN ( echo ". /usr/share/lmod/lmod/init/bash"                       \
- &&   echo ". \$SPACK_ROOT/share/spack/setup-env.sh"                \
- &&   echo "if [ \"\$CURRENTLY_BUILDING_DOCKER_IMAGE\" '!=' '1' ]"  \
- &&   echo "then"                                                   \
- &&   echo "  . \$SPACK_ROOT/share/spack/spack-completion.bash"     \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/spack.sh                                   \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-ssh.sh\""    \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-ssh.sh             \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-ssh.sh                              \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-prompt.sh\"" \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-prompt.sh          \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-prompt.sh                           \
- && mkdir -p /root/.spack                                           \
- && cp $SPACK_ROOT/share/spack/docker/modules.yaml                  \
-        /root/.spack/modules.yaml                                   \
+RUN mkdir -p /root/.spack \
+ && cp $SPACK_ROOT/share/spack/docker/modules.yaml \
+        /root/.spack/modules.yaml \
  && rm -rf /root/*.* /run/nologin $SPACK_ROOT/.git
 
 # [WORKAROUND]
@@ -66,10 +62,10 @@ RUN [ -f ~/.profile ]                                               \
  || true
 
 WORKDIR /root
-SHELL ["/bin/bash", "-l", "-c"]
+SHELL ["docker-shell"]
 
 # TODO: add a command to Spack that (re)creates the package cache
 RUN spack spec hdf5+mpi
 
 ENTRYPOINT ["/bin/bash", "/opt/spack/share/spack/docker/entrypoint.bash"]
-CMD ["docker-shell"]
+CMD ["interactive-shell"]
diff --git a/share/spack/docker/entrypoint.bash b/share/spack/docker/entrypoint.bash
index 775747d904..fbd7baf2bc 100755
--- a/share/spack/docker/entrypoint.bash
+++ b/share/spack/docker/entrypoint.bash
@@ -1,45 +1,143 @@
-#! /usr/bin/env bash -e
+#! /usr/bin/env bash
 #
 # Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-unset CURRENTLY_BUILDING_DOCKER_IMAGE
+mode=oneshot
 
-if [ "$1" '=' 'docker-shell' ] ; then
-    if [ -t 0 ] ; then
-        exec bash -il
-    else
-        (
-            echo -n "It looks like you're trying to run an intractive shell"
-            echo -n " session, but either no psuedo-TTY is allocateed for this"
-            echo -n " container's STDIN, or it is closed."
-            echo
+if [ "$( basename "$0" )" '=' 'spack-env' ] ; then
+    mode=spackenv
+elif [ "$( basename "$0" )" '=' 'docker-shell' ] ; then
+    mode=dockershell
+elif [ "$( basename "$0" )" '=' 'interactive-shell' ] ; then
+    mode=interactiveshell
+elif [ "$1" '=' 'docker-shell' ] ; then
+    mode=dockershell
+    shift
+elif [ "$1" '=' 'interactive-shell' ] ; then
+    mode=interactiveshell
+    shift
+fi
 
-            echo -n "Make sure you run docker with the --interactive and --tty"
-            echo -n " options."
-            echo
-        ) >&2
+case "$mode" in
+    "spackenv")
+        # Scenario 1: Run as if the image had no ENTRYPOINT
+        #
+        # Necessary for use cases where the command to run and all
+        # arguments must be accepted in the CMD portion. (e.g.: Gitlab CI
+        # Runners)
+        #
+        # Roughly equivalent to
+        #   docker run ... --entrypoint spack-env ... sh -c "..."
+        #
+        # The shell script runs with spack pre-loaded and ready to use.
+        . $SPACK_ROOT/share/spack/setup-env.sh
+        unset CURRENTLY_BUILDING_DOCKER_IMAGE
+        exec "$@"
+        ;;
 
-        exit 1
-    fi
-else
-    exec 3>&1
-    exec 4>&2
+    "dockershell")
+        # Scenario 2: Accept shell code from a RUN command in a
+        # Dockerfile
+        #
+        # For new Docker images that start FROM this image as its base.
+        # Prepared so that subsequent RUN commands can take advantage of
+        # Spack without having to manually (re)initialize.
+        #
+        # Example:
+        #   FROM spack/centos7
+        #   COPY spack.yaml .
+        #   RUN spack install  # <- Spack is loaded and ready to use.
+        #                      # No manual initialization necessary.
+        . $SPACK_ROOT/share/spack/setup-env.sh
+        exec bash -c "$*"
+        ;;
 
-    exec 1>&-
-    exec 2>&-
+    "interactiveshell")
+        # Scenario 3: Run an interactive shell session with Spack
+        # preloaded.
+        #
+        # Create a container meant for an interactive shell session.
+        # Additional checks are performed to ensure that stdin is a tty
+        # and additional shell completion files are sourced.  The user is
+        # presented with a shell prompt from which they may issue Spack
+        # commands.
+        #
+        # This is the default behavior when running with no CMD or
+        # ENTRYPOINT overrides:
+        #   docker run -it spack/centos7
+        if [ -t 0 ] ; then
+            . $SPACK_ROOT/share/spack/setup-env.sh
+            . $SPACK_ROOT/share/spack/spack-completion.bash
+            unset CURRENTLY_BUILDING_DOCKER_IMAGE
+            exec bash -i
+        else
+            (
+                echo -n "It looks like you're trying to run an"
+                echo -n " intractive shell session, but either no"
+                echo -n " psuedo-TTY is allocated for this container's"
+                echo    " STDIN, or it is closed."
+                echo
 
-    source /etc/profile.d/spack.sh
-    source /etc/profile.d/handle-ssh.sh
+                echo -n "Make sure you run docker with the --interactive"
+                echo -n " and --tty options."
+                echo
+            ) >&2
 
-    exec 1>&3
-    exec 2>&4
+            exit 1
+        fi
+        ;;
 
-    exec 3>&-
-    exec 4>&-
+    "oneshot")
+        # Scenario 4: Run a one-shot Spack command from the host command
+        # line.
+        #
+        # Triggered by providing arguments to `docker run`.  Arguments
+        # are passed along to the container's underlying spack
+        # installation, allowing users to use the image as if it were
+        # spack, itself.  Pass volume mount information to `docker run`
+        # to persist the effects of running in this mode.
+        #
+        # This is the default behavior when running with a CMD override.
+        #
+        # Examples:
+        #   # concretize the same spec on different OSes
+        #   docker run --rm spack/ubuntu-xenial spec zlib
+        #   docker run --rm spack/centos7 spec zlib
+        #
+        #   # a "wetter" dry-run;
+        #   # install a package and then throw away the results.
+        #   docker run --rm spack/centos7 install libiconv
+        #   docker run --rm spack/centos7 find libiconv
+        #     ==> No package matches the query: libiconv
+        #
+        #   # use docker volumes to persist changes
+        #   docker run --rm -v ...:/spack spack/centos7 install ...
+        #   docker run --rm -v ...:/spack spack/centos7 install ...
+        #   docker run --rm -v ...:/spack spack/centos7 install ...
+        exec 3>&1
+        exec 4>&2
 
-    spack "$@"
-    exit $?
-fi
+        exec 1>&-
+        exec 2>&-
+
+        . $SPACK_ROOT/share/spack/setup-env.sh
+        unset CURRENTLY_BUILDING_DOCKER_IMAGE
+
+        exec 1>&3
+        exec 2>&4
+
+        exec 3>&-
+        exec 4>&-
+
+        spack "$@"
+        exit $?
+        ;;
+
+    *)
+        echo "INTERNAL ERROR - UNRECOGNIZED MODE: $mode" >&2
+        exit 1
+        ;;
+esac
diff --git a/share/spack/docker/handle-prompt.sh b/share/spack/docker/handle-prompt.sh
deleted file mode 100644
index a01047463e..0000000000
--- a/share/spack/docker/handle-prompt.sh
+++ /dev/null
@@ -1,173 +0,0 @@
-# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
-# Spack Project Developers. See the top-level COPYRIGHT file for details.
-#
-# SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
-if [ "$CURRENTLY_BUILDING_DOCKER_IMAGE" '!=' '1' ] ; then
-
-if [ x$SPACK_PROMPT '!=' x0 ] ; then
-
-__tmp="`mktemp -d`"
-
-__trylock() {
-    local dir
-    dir="$__tmp/$1.lock"
-    mkdir "$dir" &>/dev/null
-    return $?
-}
-
-__queue_init() {
-    local r
-    local w
-
-    mkdir "$__tmp/$1.read.lock" ; r=$?
-    mkdir "$__tmp/$1.write.lock" ; w=$?
-
-    if [ "$r" '=' '0' -a "$w" '=' '0' ] ; then
-        return 0
-    else
-        return 1
-    fi
-}
-
-__queue_try_read() {
-    __trylock "$1.read"
-    return $?
-}
-
-__queue_try_write() {
-    __trylock "$1.write"
-    return $?
-}
-
-__queue_make_readable() {
-    rm -r "$__tmp/$1.read.lock" &>/dev/null
-    return $?
-}
-
-__queue_make_writable() {
-    rm -r "$__tmp/$1.write.lock" &>/dev/null
-    return $?
-}
-
-__read() {
-    cat "$__tmp/$1" 2> /dev/null
-    return $?
-}
-
-__write() {
-    cat > "$__tmp/$1" 2> /dev/null
-    return $?
-}
-
-__revparse_head() {
-    head="`git -C "$SPACK_ROOT" rev-parse $@ HEAD 2>/dev/null`"
-    result="$?"
-    if [ "$result" '!=' '0' ] ; then
-        head="`git --git-dir="$SPACK_ROOT"/.git \\
-              --work-tree="$SPACK_ROOT" rev-parse $@ HEAD 2>/dev/null`"
-        result="$?"
-    fi
-
-    echo "$head"
-    return $result
-}
-
-__git_head() {
-    head="`__revparse_head --abbrev-ref`"
-    if [ "$?" '=' '0' ] ; then
-        if [ "$head" '=' 'HEAD' ] ; then
-            head="`__revparse_head | cut -c1-8`..."
-        fi
-
-        echo "$head"
-    fi
-}
-
-__update_prompt() {
-    local prompt
-    prompt=''
-    linux_distro="$DOCKERFILE_DISTRO"
-    if [ -n "$linux_distro" ] ; then
-        linux_distro='\[\e[1;34m\][\[\e[0;34m\]'"$linux_distro"'\[\e[1;34m\]]'
-        if [ -n "$prompt" ] ; then
-            prompt="$prompt "
-        fi
-        prompt="$prompt$linux_distro"
-    fi
-
-    git_head="`__git_head`"
-
-    if [ -n "$git_head" ] ; then
-        git_head='\[\e[1;32m\](\[\e[0;32m\]'"$git_head"'\[\e[1;32m\])'
-        if [ -n "$prompt" ] ; then
-            prompt="$prompt "
-        fi
-        prompt="$prompt$git_head"
-    fi
-
-    if [ -n "$prompt" ] ; then
-        prompt="$prompt "
-    fi
-    prompt="$prompt"'\[\e[0;m\]\W: '
-    echo "$prompt" | __write prompt
-}
-
-set -m
-(
-    __queue_init query
-    __queue_init prompt
-
-    __update_prompt
-    __queue_make_readable prompt
-
-    __queue_make_writable query
-
-    while sleep 0.010 ; do
-        last_q_time=''
-
-        while sleep 0.010 ; do
-            q_time="`date +%s%N`"
-            if __queue_try_read query ; then
-                last_q_time="$q_time"
-                __queue_make_writable query
-            fi
-
-            if [ -n "$last_q_time" -a \
-                "$(( (q_time - last_q_time)/10000000 > 100 ))" '=' '1' ] ; then
-                break
-            fi
-        done
-
-        __update_prompt
-        __queue_make_readable prompt
-    done
-) &>/dev/null &
-set +m
-
-__update_prompt_main_first_call=1
-__update_prompt_main() {
-    if [ "$__update_prompt_main_first_call" '=' '1' ] ; then
-        while sleep 0.001 ; do
-            if __queue_try_read prompt ; then
-                PS1="`__read prompt`"
-                break
-            fi
-        done
-        __update_prompt_main_first_call=0
-    else
-        if __queue_try_read prompt ; then
-            PS1="`__read prompt`"
-        fi
-    fi
-
-    if __queue_try_write query ; then
-        __queue_make_readable query
-    fi
-}
-
-PROMPT_COMMAND=__update_prompt_main
-
-fi # [ x$SPACK_PROMPT '!=' x0 ]
-
-fi # [ "$CURRENTLY_BUILDING_DOCKER_IMAGE" '!=' '1' ]
diff --git a/share/spack/docker/handle-ssh.sh b/share/spack/docker/handle-ssh.sh
deleted file mode 100644
index 18e5ae259d..0000000000
--- a/share/spack/docker/handle-ssh.sh
+++ /dev/null
@@ -1,50 +0,0 @@
-# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
-# Spack Project Developers. See the top-level COPYRIGHT file for details.
-#
-# SPDX-License-Identifier: (Apache-2.0 OR MIT)
-
-if [ "$CURRENTLY_BUILDING_DOCKER_IMAGE" '!=' '1' ] ; then
-
-uid="`id -u`"
-if [ "$uid" '=' '0' ] ; then
-    key_types="dsa ecdsa rsa"
-    if [ "$DOCKERFILE_BASE" '!=' 'centos:6' ] ; then
-        key_types="${key_types} ed25519"
-    fi
-
-    for key_type in $key_types ; do
-        private_key_file="/etc/ssh/ssh_host_${key_type}_key"
-        public_key_file="$private_key_file.pub"
-
-        if [ '!' -f "$private_key_file" ] ; then
-            ssh-keygen \
-                -q -t "$key_type" -N "" -f "$private_key_file"
-            chmod 600 "$private_key_file"
-            chmod 644 "$public_key_file"
-        fi
-    done
-
-    mkdir -p /var/run/sshd
-
-    pgrep -u 0 -U 0 sshd &> /dev/null
-    if [ '!' "$?" '=' '0' ] ; then
-        nohup /usr/sbin/sshd -f /etc/ssh/sshd_config < /dev/null &> /dev/null
-    fi
-fi
-
-if [ '!' -f "$HOME/.ssh/id_rsa" ] ; then
-    ssh-keygen \
-        -t rsa -C "spack.developer@docker.host" -N "" -f "$HOME/.ssh/id_rsa"
-    cat "$HOME/.ssh/id_rsa.pub" >> "$HOME/.ssh/authorized_keys"
-    chmod 600 "$HOME/.ssh/authorized_keys"
-
-    docker_ip="`ip address show dev eth0 |
-                grep inet |
-                cut -d' ' -f 6 |
-                cut -d/ -f 1`"
-
-    ssh-keyscan -t rsa 127.0.0.1 localhost "$docker_ip" "`hostname`" \
-        > "$HOME/.ssh/known_hosts" 2> /dev/null
-fi
-
-fi # [ "$CURRENTLY_BUILDING_DOCKER_IMAGE" '!=' '1' ]
diff --git a/share/spack/docker/ubuntu-1604.dockerfile b/share/spack/docker/ubuntu-1604.dockerfile
index e7a6783d24..7891c5a261 100644
--- a/share/spack/docker/ubuntu-1604.dockerfile
+++ b/share/spack/docker/ubuntu-1604.dockerfile
@@ -16,29 +16,35 @@ COPY share $SPACK_ROOT/share
 COPY var   $SPACK_ROOT/var
 RUN mkdir -p $SPACK_ROOT/opt/spack
 
-RUN apt-get -yqq update                           \
- && apt-get -yqq install --no-install-recommends  \
-        build-essential                           \
-        ca-certificates                           \
-        curl                                      \
-        file                                      \
-        g++                                       \
-        gcc                                       \
-        gfortran                                  \
-        git                                       \
-        gnupg2                                    \
-        iproute2                                  \
-        lmod                                      \
-        locales                                   \
-        lua-posix                                 \
-        make                                      \
-        openssh-server                            \
-        python3                                   \
-        python3-pip                               \
-        tcl                                       \
-        unzip                                     \
- && locale-gen en_US.UTF-8                        \
- && pip3 install boto3                            \
+RUN ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/docker-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/interactive-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/spack-env
+
+RUN apt-get -yqq update \
+ && apt-get -yqq install --no-install-recommends \
+        build-essential \
+        ca-certificates \
+        curl \
+        file \
+        g++ \
+        gcc \
+        gfortran \
+        git \
+        gnupg2 \
+        iproute2 \
+        lmod \
+        locales \
+        lua-posix \
+        make \
+        python3 \
+        python3-pip \
+        tcl \
+        unzip \
+ && locale-gen en_US.UTF-8 \
+ && pip3 install boto3 \
  && rm -rf /var/lib/apt/lists/*
 
 # Add LANG default to en_US.UTF-8
@@ -46,33 +52,10 @@ ENV LANGUAGE en_US.UTF-8
 ENV LANG en_US.UTF-8
 ENV LC_ALL en_US.UTF-8
 
-RUN ( echo ". /usr/share/lmod/lmod/init/bash"                       \
- &&   echo ". \$SPACK_ROOT/share/spack/setup-env.sh"                \
- &&   echo "if [ \"\$CURRENTLY_BUILDING_DOCKER_IMAGE\" '!=' '1' ]"  \
- &&   echo "then"                                                   \
- &&   echo "  . \$SPACK_ROOT/share/spack/spack-completion.bash"     \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/spack.sh                                   \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-ssh.sh\""    \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-ssh.sh             \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-ssh.sh                              \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-prompt.sh\"" \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-prompt.sh          \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-prompt.sh                           \
- && mkdir -p /root/.spack                                           \
- && cp $SPACK_ROOT/share/spack/docker/modules.yaml                  \
-        /root/.spack/modules.yaml                                   \
- && rm -rf /root/*.* $SPACK_ROOT/.git
+RUN mkdir -p /root/.spack \
+ && cp $SPACK_ROOT/share/spack/docker/modules.yaml \
+        /root/.spack/modules.yaml \
+ && rm -rf /root/*.* /run/nologin $SPACK_ROOT/.git
 
 # [WORKAROUND]
 # https://superuser.com/questions/1241548/
@@ -82,10 +65,10 @@ RUN [ -f ~/.profile ]                                               \
  || true
 
 WORKDIR /root
-SHELL ["/bin/bash", "-l", "-c"]
+SHELL ["docker-shell"]
 
 # TODO: add a command to Spack that (re)creates the package cache
 RUN spack spec hdf5+mpi
 
 ENTRYPOINT ["/bin/bash", "/opt/spack/share/spack/docker/entrypoint.bash"]
-CMD ["docker-shell"]
+CMD ["interactive-shell"]
diff --git a/share/spack/docker/ubuntu-1804.dockerfile b/share/spack/docker/ubuntu-1804.dockerfile
index 5950908e1e..c079331476 100644
--- a/share/spack/docker/ubuntu-1804.dockerfile
+++ b/share/spack/docker/ubuntu-1804.dockerfile
@@ -16,29 +16,35 @@ COPY share $SPACK_ROOT/share
 COPY var   $SPACK_ROOT/var
 RUN mkdir -p $SPACK_ROOT/opt/spack
 
-RUN apt-get -yqq update                           \
- && apt-get -yqq install --no-install-recommends  \
-        build-essential                           \
-        ca-certificates                           \
-        curl                                      \
-        file                                      \
-        g++                                       \
-        gcc                                       \
-        gfortran                                  \
-        git                                       \
-        gnupg2                                    \
-        iproute2                                  \
-        lmod                                      \
-        locales                                   \
-        lua-posix                                 \
-        make                                      \
-        openssh-server                            \
-        python3                                   \
-        python3-pip                               \
-        tcl                                       \
-        unzip                                     \
- && locale-gen en_US.UTF-8                        \
- && pip3 install boto3                            \
+RUN ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/docker-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/interactive-shell \
+ && ln -s $SPACK_ROOT/share/spack/docker/entrypoint.bash \
+          /usr/local/bin/spack-env
+
+RUN apt-get -yqq update \
+ && apt-get -yqq install --no-install-recommends \
+        build-essential \
+        ca-certificates \
+        curl \
+        file \
+        g++ \
+        gcc \
+        gfortran \
+        git \
+        gnupg2 \
+        iproute2 \
+        lmod \
+        locales \
+        lua-posix \
+        make \
+        python3 \
+        python3-pip \
+        tcl \
+        unzip \
+ && locale-gen en_US.UTF-8 \
+ && pip3 install boto3 \
  && rm -rf /var/lib/apt/lists/*
 
 # Add LANG default to en_US.UTF-8
@@ -46,33 +52,10 @@ ENV LANGUAGE en_US.UTF-8
 ENV LANG en_US.UTF-8
 ENV LC_ALL en_US.UTF-8
 
-RUN ( echo ". /usr/share/lmod/lmod/init/bash"                       \
- &&   echo ". \$SPACK_ROOT/share/spack/setup-env.sh"                \
- &&   echo "if [ \"\$CURRENTLY_BUILDING_DOCKER_IMAGE\" '!=' '1' ]"  \
- &&   echo "then"                                                   \
- &&   echo "  . \$SPACK_ROOT/share/spack/spack-completion.bash"     \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/spack.sh                                   \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-ssh.sh\""    \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-ssh.sh             \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-ssh.sh                              \
- && ( echo "f=\"\$SPACK_ROOT/share/spack/docker/handle-prompt.sh\"" \
- &&   echo "if [ -f \"\$f\" ]"                                      \
- &&   echo "then"                                                   \
- &&   echo "  .  \"\$f\""                                           \
- &&   echo "else"                                                   \
- &&   cat  $SPACK_ROOT/share/spack/docker/handle-prompt.sh          \
- &&   echo "fi"                                                   ) \
-       >> /etc/profile.d/handle-prompt.sh                           \
- && mkdir -p /root/.spack                                           \
- && cp $SPACK_ROOT/share/spack/docker/modules.yaml                  \
-        /root/.spack/modules.yaml                                   \
- && rm -rf /root/*.* $SPACK_ROOT/.git
+RUN mkdir -p /root/.spack \
+ && cp $SPACK_ROOT/share/spack/docker/modules.yaml \
+        /root/.spack/modules.yaml \
+ && rm -rf /root/*.* /run/nologin $SPACK_ROOT/.git
 
 # [WORKAROUND]
 # https://superuser.com/questions/1241548/
@@ -86,10 +69,10 @@ RUN [ -f ~/.profile ]                                               \
 RUN ln -s posix_c.so /usr/lib/x86_64-linux-gnu/lua/5.2/posix.so
 
 WORKDIR /root
-SHELL ["/bin/bash", "-l", "-c"]
+SHELL ["docker-shell"]
 
 # TODO: add a command to Spack that (re)creates the package cache
 RUN spack spec hdf5+mpi
 
 ENTRYPOINT ["/bin/bash", "/opt/spack/share/spack/docker/entrypoint.bash"]
-CMD ["docker-shell"]
+CMD ["interactive-shell"]