From 43e8730ffe1d756c18800c09a366af55e75065eb Mon Sep 17 00:00:00 2001
From: Thilo Fromm <thilo@kinvolk.io>
Date: Fri, 7 Jan 2022 11:06:30 +0100
Subject: [PATCH] sdk_container: better docker / podman detection

In bce3bd9031fa78c79173f29bcac5bc49c81a03b4, we added support for podman
for building and running the SDK container. The presence of podman is
auto-detected in sdk_container_common.sh. However, podman is preverred
over docker, requiring users to use *sudo* (which podman requires and
docker does not).

This change uses docker when present, podman otherwise. It also improves
podman detection - 'podman' uses argv[0] in its version string, so if
'docker' is a symlink to 'podman', 'podman --version' output uses
'docker'. This broke the SDK container on hosts which have a 'docker'
symlink to 'podman' since 'podman' is then run w/o 'sudo'.

Signed-off-by: Thilo Fromm <thilo@kinvolk.io>
---
 sdk_lib/sdk_container_common.sh | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/sdk_lib/sdk_container_common.sh b/sdk_lib/sdk_container_common.sh
index c889301a0b..11325ff6dc 100644
--- a/sdk_lib/sdk_container_common.sh
+++ b/sdk_lib/sdk_container_common.sh
@@ -11,10 +11,27 @@ sdk_container_common_versionfile="sdk_container/.repo/manifests/version.txt"
 sdk_container_common_registry="ghcr.io/flatcar-linux"
 sdk_container_common_env_file="sdk_container/.sdkenv"
 
+# Check for podman and docker; use docker if present, podman alternatively.
+# Podman needs 'sudo' since we need privileged containers for the SDK.
+
 is_podman=false
 if command -v podman >/dev/null; then
-  is_podman=true
+    # podman is present
+    if command -v docker >/dev/null ; then
+        # docker is present, too
+        if docker help | grep -q -i podman; then
+            # "docker" is actually podman.
+            # NOTE that 'docker --version' does not reliably work for podman detection
+            #  since 'podman' uses argv[0] in its version string.
+            #  A symlink docker->podman will result in 'podman' using the 'docker' argv[0].
+            is_podman=true
+        fi
+    else
+        # docker is not present
+        is_podman=true
+    fi
 fi
+
 docker="docker"
 if "${is_podman}"; then
   docker="sudo podman"