diff --git a/Dockerfile.pdflatex b/Dockerfile.pdflatex
new file mode 100644
index 0000000..ad37a42
--- /dev/null
+++ b/Dockerfile.pdflatex
@@ -0,0 +1,8 @@
+FROM sphinxdoc/sphinx-pdflatex:4.3.2
+
+LABEL "maintainer"="Ammar Askar <ammar@ammaraskar.com>"
+
+ADD entrypoint.py /entrypoint.py
+ADD sphinx_action /sphinx_action
+
+ENTRYPOINT ["/entrypoint.py"]
diff --git a/Dockerfile.sphinx4 b/Dockerfile.sphinx4
new file mode 100644
index 0000000..c665b66
--- /dev/null
+++ b/Dockerfile.sphinx4
@@ -0,0 +1,8 @@
+FROM sphinxdoc/sphinx:4.3.2
+
+LABEL "maintainer"="Ammar Askar <ammar@ammaraskar.com>"
+
+ADD entrypoint.py /entrypoint.py
+ADD sphinx_action /sphinx_action
+
+ENTRYPOINT ["/entrypoint.py"]
diff --git a/action.yml b/action.yml
index a914bdf..ce825a1 100644
--- a/action.yml
+++ b/action.yml
@@ -21,6 +21,24 @@ inputs:
       dependencies, for example with
       "apt-get update -y && apt-get install -y perl"
     required: false
+  update:
+    description:
+      Set this flag to run 'apt update' in the container before starting
+      the sphinx build.
+    required: false
+    default: false
+  install:
+    description:
+      A list of additional 'apt' packages to install before running
+      sphinx. (Setting this will force-enable 'update' as well.)
+    required: false
+  container:
+    description:
+      Run the build in the named container. Must be one of
+      'sphinx4', 'pdflatex', or 'default'.
+    required: false
+    default: 'default'
 runs:
   using: 'docker'
-  image: 'Dockerfile'
\ No newline at end of file
+  image: ${{ format('Dockerfile.{0}', inputs.container) }}
+
diff --git a/entrypoint.py b/entrypoint.py
index 1d3416d..72e3163 100755
--- a/entrypoint.py
+++ b/entrypoint.py
@@ -1,14 +1,38 @@
-#!/usr/bin/env python3
+#!/usr/bin/env -S python3 -u
 import os
 import json
+import subprocess
+import sys
 from sphinx_action import action
 
 # This is the entrypoint called by Github when our action is run. All the
 # Github specific setup is done here to make it easy to test the action code
 # in isolation.
+
+
+def interpret_env(env_var):
+    if isinstance(env_var, str):
+        return env_var.lower() not in ["false", "no", "off" "0"]
+    return bool(env_var)
+
+
 if __name__ == "__main__":
     print("[sphinx-action] Starting sphinx-action build.")
 
+    update = os.environ.get("INPUT_UPDATE", False)
+    should_update = interpret_env(update)
+
+    install = os.environ.get("INPUT_INSTALL", "")
+    packages = install.split()
+
+    if should_update or packages:
+        print("Updating apt...")
+        subprocess.call(["/usr/bin/apt", "-y", "update"])
+
+    print(f"{len(packages)} packages (plus dependencies) to install")
+    if packages:
+        subprocess.call(["/usr/bin/apt", "-y", "install", *packages])
+
     if "INPUT_PRE-BUILD-COMMAND" in os.environ:
         pre_command = os.environ["INPUT_PRE-BUILD-COMMAND"]
         print("Running: {}".format(pre_command))