support (rootless) podman container engine

Author: mr-c

.github/workflows/ci-tests.yml

@@ -123,7 +123,7 @@ jobs:
     strategy:
       matrix:
         cwl-version: [v1.0, v1.1, v1.2]
-        container: [docker, singularity]
+        container: [docker, singularity, podman]
 
     steps:
       - uses: actions/checkout@v2

conformance-test.sh

@@ -44,7 +44,11 @@ if [ ! -d "${repo}-${spec_branch}" ]; then
 fi
 
 if [ "${container}" == "docker" ]; then
-    docker pull node:slim
+    docker pull docker.io/node:slim
+fi
+
+if [ "${container}" == "podman" ]; then
+    podman pull docker.io/node:slim
 fi
 
 venv cwltool-venv3
@@ -109,6 +113,8 @@ if [[ "$container" = "singularity" ]]; then
         # See issue #1440
         exclusions+=(stdin_shorcut)
     fi
+elif [[ "$container" = "podman" ]]; then
+    EXTRA+=" --podman"
 fi
 
 if [ -n "$EXTRA" ]

cwltool/argparser.py

@@ -435,6 +435,12 @@ def arg_parser() -> argparse.ArgumentParser:
         "version v3.18+ or with overlayfs support "
         "backported.",
     )
+    dockergroup.add_argument(
+        "--podman",
+        action="store_true",
+        default=False,
+        help="[experimental] Use " "Podman runtime for running containers. ",
+    )
     dockergroup.add_argument(
         "--no-container",
         action="store_false",

cwltool/context.py

@@ -110,6 +110,7 @@ def __init__(self, kwargs: Optional[Dict[str, Any]] = None) -> None:
         self.streaming_allowed: bool = False
 
         self.singularity = False  # type: bool
+        self.podman = False  # type: bool
         self.debug = False  # type: bool
         self.compute_checksum = True  # type: bool
         self.name = ""  # type: str

cwltool/docker.py

@@ -1,4 +1,4 @@
-"""Enables Docker software containers via the {u,}docker runtimes."""
+"""Enables Docker software containers via the {u,}docker or podman runtimes."""
 
 import csv
 import datetime
@@ -339,6 +339,8 @@ def create_runtime(
                 # without this
             else:
                 runtime = [user_space_docker_cmd, "run"]
+        elif runtimeContext.podman:
+            runtime = ["podman", "run", "-i", "--userns=keep-id"]
         else:
             runtime = ["docker", "run", "-i"]
         self.append_volume(