Add the Podman backend.

Makefile.am

@@ -16,6 +16,7 @@ odkrun_SOURCES = src/odkrun.c \
 		 src/backend.h \
 		 src/backend-docker.c src/backend-docker.h \
 		 src/backend-singularity.c src/backend-singularity.h \
+		 src/backend-podman.c src/backend-podman.h \
 		 src/backend-native.c src/backend-native.h \
 		 src/backend-apple.c src/backend-apple.h \
 		 src/owlapi.c src/owlapi.h src/owlapi-options.h \

README.md

@@ -107,7 +107,7 @@ by the ODK workflows.
 Currently, four different backends are supported: Docker, Singularity,
 Apple Container, and “native” environments.
 
-### Docker, Singularity, and Apple Container
+### Docker, Singularity, Podman, and Apple Container
 
 Docker is the primary backend, and the most well supported. Unless
 configured otherwise at build time (option `--with-default-backend`),
@@ -118,17 +118,22 @@ in an ephemeral container based on that image.
 The exact image used may be specified using the `--image` (`-i`) and
 `--tag` (`-t`) option; the default is `obolibrary/odkfull:latest`.
 
-The Singularity and Apple Container backends rely on the same Docker
-images, but used through the [Singularity container
-platform](https://docs.sylabs.io/guides/latest/user-guide/#) or the
-[Apple `container` tool](https://github.com/apple/container),
-respectively. As its name may imply, the Apple Container backend is only
-available on macOS.
-
-Use the `--singularity` (`-s`) option to select the Singularity backend,
-and the `--apple` (`-a`) option to select the Apple Container backend.
-The image to use may be selected using the same `-i` and `-t` options as
-for the Docker backend.
+Several other backends are available, that rely on the same Docker
+images, but used through other containerization tools. The table below
+lists the available backends along with the command-line options that
+select them:
+
+| Backend | Option |
+| ------- | ------ |
+| [Singularity](https://docs.sylabs.io/guides/latest/user-guide/#) | `--singularity` (`-s`) |
+| [Podman](https://podman.io/) | `--podman` (`-p`) |
+| [Apple Container](https://github.com/apple/container) | `--apple` (`a`) |
+
+As its name may imply, the Apple Container backend is only available on
+macOS.
+
+With all those backends, the image to use may be selected using the same
+`-i` and `-t` options as for the Docker backend.
 
 ### Native backend
 

configure.ac

@@ -46,12 +46,13 @@ AC_DEFINE_UNQUOTED([ODK_EXECUTABLE], ["$with_odk_executable"], [Name or path of
 dnl Default backend
 AC_ARG_WITH([default-backend],
             [AS_HELP_STRING([--with-default-backend],
-                            [Name of the backend to use by default. One of docker, singularity, apple, native, or none.])],
+                            [Name of the backend to use by default. One of docker, singularity, podman, apple, native, or none.])],
             [],
             [with_default_backend=docker])
 AS_CASE([$with_default_backend],
         [docker],      [AC_DEFINE([ODK_DEFAULT_BACKEND], [odk_backend_docker_init], [Docker backend])],
         [singularity], [AC_DEFINE([ODK_DEFAULT_BACKEND], [odk_backend_singularity_init], [Singularity backend])],
+        [podman],      [AC_DEFINE([ODK_DEFAULT_BACKEND], [odk_backend_podman_init], [Podman backend])],
         [apple],       [AC_DEFINE([ODK_DEFAULT_BACKEND], [odk_backend_apple_init], [Apple Container backend])],
         [native],      [AC_DEFINE([ODK_DEFAULT_BACKEND], [odk_backend_native_init], [Native backend])],
         [none],        [AC_DEFINE([ODK_DEFAULT_BACKEND], [NULL], [No default backend])],

doc/odkrun.1.in

@@ -15,6 +15,7 @@ odkrun - ODK Runner tool
 .RB [ -l | --lite ]
 .RB [ -D | --docker ]
 .RB [ -s | --singulary ]
+.RB [ -p | --podman ]
 .RB [ -a | --apple ]
 .RB [ -n | --native ]
 .RB [ --root ]
@@ -71,6 +72,10 @@ backend, unless specified otherwise at configure time.
 Run the container with Singularity rather than Docker. This
 is experimental but should mostly work.
 .TP
+.BR -p ", " --podman
+Run the container with Podman rather than Docker. This is
+experimental but should mostly work.
+.TP
 .BR -a ", " --apple
 Run the container with Apple Container rather than Docker.
 This is only available on macOS. This is experimental but

src/backend-podman.c

@@ -0,0 +1,122 @@
+/*
+ * ODK Runner
+ * Copyright (C) 2026 Damien Goutte-Gattat
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+ * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+ * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include "backend-podman.h"
+
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+
+#if defined(ODK_RUNNER_LINUX)
+#include <unistd.h> /* for getuid/getgid */
+#endif
+
+#include "backend-docker.h"
+
+static int
+prepare(odk_backend_t *backend, odk_run_config_t *cfg)
+{
+    (void) backend;
+
+    if ( (cfg->flags & ODK_FLAG_RUNASROOT) == 0 ) {
+#if defined(ODK_RUNNER_LINUX)
+        char *user_id = mr_sprintf(NULL, "%u", getuid());
+        char *group_id = mr_sprintf(NULL, "%u", getgid());
+#else
+        char *user_id = "1000";
+        char *group_id = "1000";
+#endif
+
+        odk_add_env_var(cfg, "ODK_USER_ID", user_id, 0);
+        odk_add_env_var(cfg, "ODK_GROUP_ID", group_id, 0);
+    }
+
+    return 0;
+}
+
+static int
+run(odk_backend_t *backend, odk_run_config_t *cfg, char **command)
+{
+    int rc;
+    char **argv;
+    mem_registry_t mr = { 0 };
+
+    (void) backend;
+
+    argv = odk_backend_docker_build_command(&mr, cfg, command);
+    argv[0] = "podman";
+    rc = spawn_process(argv);
+    mr_free(&mr);
+
+    return rc;
+}
+
+static int
+close_backend(odk_backend_t *backend)
+{
+    (void) backend;
+
+    return 0;
+}
+
+static int
+get_total_memory(odk_backend_info_t *info)
+{
+    FILE *p;
+    int ret = -1;
+
+    if ( (p = popen("podman info --format={{.Host.MemTotal}}", "r")) != NULL ) {
+        if ( fscanf(p, "%lu", &(info->total_memory)) == 1 )
+            ret = 0;
+        else
+            errno = ESRCH;
+        pclose(p);
+    }
+
+    return ret;
+}
+
+int
+odk_backend_podman_init(odk_backend_t *backend)
+{
+    int ret;
+
+    backend->prepare = prepare;
+    backend->run = run;
+    backend->close = close_backend;
+
+    ret = get_total_memory(&(backend->info));
+
+    return ret;
+}

src/backend-podman.h

@@ -0,0 +1,52 @@
+/*
+ * ODK Runner
+ * Copyright (C) 2026 Damien Goutte-Gattat
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+ * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+ * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+ * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef ICP20261007_BACKEND_PODMAN_H
+#define ICP20261007_BACKEND_PODMAN_H
+
+#include <memreg.h>
+
+#include "backend.h"
+#include "procutil.h"
+
+#ifdef __cpluscplus
+extern "C" {
+#endif
+
+int
+odk_backend_podman_init(odk_backend_t *);
+
+#define odk_backend_podman_available()  check_process("podman", "--version")
+
+#ifdef __cpluscplus
+}
+#endif
+
+#endif /* !ICP20261007_BACKEND_PODMAN_H */

src/odkrun.c

@@ -47,8 +47,9 @@
 #include "util.h"
 #include "backend-docker.h"
 #include "backend-singularity.h"
-#include "backend-native.h"
+#include "backend-podman.h"
 #include "backend-apple.h"
+#include "backend-native.h"
 #include "oaklib.h"
 #include "owlapi.h"
 #include "runconf.h"
@@ -85,6 +86,8 @@ Start a ODK container.\n");
     -D, --docker        Run the container with Docker. This is normally\n\
                         the default.\n\
     -s, --singularity   Run the container with Singularity rather\n\
+                        than Docker (experimental).\n\
+    -p, --podman        Run the container with Podman rather than\n\
                         than Docker (experimental).");
 #if defined(ODK_RUNNER_MACOS)
     puts("\
@@ -462,6 +465,7 @@ main(int argc, char **argv)
         { "lite",           0, NULL, 'l' },
         { "docker",         0, NULL, 'D' },
         { "singularity",    0, NULL, 's' },
+        { "podman",         0, NULL, 'p' },
 #if defined (ODK_RUNNER_MACOS)
         { "apple",          0, NULL, 'a' },
 #endif
@@ -484,7 +488,7 @@ main(int argc, char **argv)
 
     odk_init_config(&cfg);
 
-    while ( (c = getopt_long(argc, argv, "+hvdi:t:lse:k:Km:D" BACKEND_OPTS,
+    while ( (c = getopt_long(argc, argv, "+hvdi:t:lse:k:Km:Dp" BACKEND_OPTS,
                              options, NULL)) != -1 ) {
         switch ( c ) {
         case 'h':
@@ -524,6 +528,10 @@ main(int argc, char **argv)
             backend_init = odk_backend_singularity_init;
             break;
 
+        case 'p':
+            backend_init = odk_backend_podman_init;
+            break;
+
 #if !defined(ODK_RUNNER_WINDOWS)
         case 'n':
             backend_init = odk_backend_native_init;
@@ -597,6 +605,8 @@ main(int argc, char **argv)
             backend_init = odk_backend_docker_init;
         else if ( odk_backend_singularity_available() )
             backend_init = odk_backend_singularity_init;
+        else if ( odk_backend_podman_available() )
+            backend_init = odk_backend_podman_init;
         else if ( odk_backend_apple_available() )
             backend_init = odk_backend_apple_init;
         else if ( odk_backend_native_available() )