Revert "Avoid running executable to verify if docker is correctly ins…

…talled and clarify documentation for `jib.dockerClient.executable` (#3742)" (#3743)

This reverts commit 0e731e2.

jib-core/src/main/java/com/google/cloud/tools/jib/docker/CliDockerClient.java

@@ -103,8 +103,8 @@ public List<DescriptorDigest> getDiffIds() throws DigestException {
   public static final Path DEFAULT_DOCKER_CLIENT = Paths.get("docker");
 
   /**
-   * Checks if Docker is installed on the user's system by verifying if the executable path provided
-   * exists and the JVM has the appropriate permissions to execute it.
+   * Checks if Docker is installed on the user's system and accessible by running the default {@code
+   * docker} command.
    *
    * @return {@code true} if Docker is installed on the user's system and accessible
    */
@@ -113,14 +113,20 @@ public static boolean isDefaultDockerInstalled() {
   }
 
   /**
-   * Checks if Docker is installed on the user's system and by verifying if the executable path
-   * provided exists and the JVM has the appropriate permissions to execute it.
+   * Checks if Docker is installed on the user's system and accessible by running the given {@code
+   * docker} executable.
    *
    * @param dockerExecutable path to the executable to test running
    * @return {@code true} if Docker is installed on the user's system and accessible
    */
   public static boolean isDockerInstalled(Path dockerExecutable) {
-    return Files.isExecutable(dockerExecutable);
+    try {
+      new ProcessBuilder(dockerExecutable.toString()).start();
+      return true;
+
+    } catch (IOException ex) {
+      return false;
+    }
   }
 
   /**

jib-gradle-plugin/README.md

@@ -290,7 +290,7 @@ Property | Type | Default | Description
 
 Property | Type | Default | Description
 --- | --- | --- | ---
-`executable` | `File` | `docker` | Sets the path to the Docker executable that is called to load the image into the Docker daemon. **Please note**: Users are responsible for ensuring that the Docker path passed in is valid and has the right permissions to be executed.
+`executable` | `File` | `docker` | Sets the path to the Docker executable that is called to load the image into the Docker daemon.
 `environment` | `Map<String, String>` | *None* | Sets environment variables used by the Docker executable.
 
 #### System Properties

jib-maven-plugin/README.md

@@ -341,7 +341,7 @@ Property | Type | Default | Description
 
 Property | Type | Default | Description
 --- | --- | --- | ---
-`executable` | string | `docker` | Sets the path to the Docker executable that is called to load the image into the Docker daemon. **Please note**: Users are responsible for ensuring that the Docker path passed in is valid and has the right permissions to be executed.
+`executable` | string | `docker` | Sets the path to the Docker executable that is called to load the image into the Docker daemon.
 `environment` | map | *None* | Sets environment variables used by the Docker executable.
 
 #### System Properties