quarkusio/quarkus · error · MojoExecutionException

Failed to create <classesDir>

Error message

Failed to create <classesDir>

What it means

ensureResolvableModule walks the dependency tree and creates target/classes directories for workspace modules whose output dirs are missing so artifacts become resolvable. If Files.createDirectories fails with an IOException, this MojoExecutionException is thrown wrapping it.

Source

Thrown at devtools/maven/src/main/java/io/quarkus/maven/GoOfflineMojo.java:159

        if (artifact != null) {
            final LocalProject module = workspace.getProject(artifact.getGroupId(), artifact.getArtifactId());
            if (module != null && !module.getRawModel().getPackaging().equals(ArtifactCoords.TYPE_POM)) {
                final Path classesDir;
                if (artifact.getClassifier().equals(ArtifactSources.TEST)) {
                    classesDir = module.getTestClassesDir();
                } else {
                    classesDir = module.getClassesDir();
                }
                if (!Files.exists(classesDir)) {
                    Path topDirToCreate = classesDir;
                    while (!Files.exists(topDirToCreate.getParent())) {
                        topDirToCreate = topDirToCreate.getParent();
                    }
                    try {
                        Files.createDirectories(classesDir);
                        createdDirs.add(topDirToCreate);
                    } catch (IOException e) {
                        throw new MojoExecutionException("Failed to create " + classesDir, e);
                    }
                }
            }
        }
        for (DependencyNode c : node.getChildren()) {
            ensureResolvableModule(c, workspace, createdDirs);
        }
    }
}

View on GitHub (pinned to e1c734241f)

Solutions

1. Check filesystem permissions on the project target/ directories and fix ownership
2. Verify the path is not an existing regular file (delete it if so)
3. Free disk space if the disk is full
4. Run the build inside the same user context that owns the workspace
5. Check container/SELinux policies if on a restricted system

Example fix

// before
$ mvn quarkus:go-offline  # fails creating module/target/classes
// after
$ sudo chown -R $(whoami) . && mvn quarkus:go-offline

// pre-check target dir writability
Path target = Path.of("target");
if (Files.exists(target) && !Files.isWritable(target)) {
    throw new IllegalStateException("target/ is not writable: " + target);
}
if (Files.exists(target) && !Files.isDirectory(target)) {
    throw new IllegalStateException("target exists but is not a directory");
}

When it happens

Trigger: Running `mvn quarkus:go-offline` when a module's target/classes path cannot be created — typically a filesystem permission problem, path is actually a file, or read-only filesystem.

Common situations: Running the build as a different user than the workspace owner; Docker container with read-only volume; SELinux/AppArmor denials; disk full on CI runners.

Related errors

• Unable to create directory: ${directory}
• Unable to collect the target directories
• Could not create directory ${outputDirectory}
• Could not create directory ${outputDirectory}
• Failed to create the output dir ${projectFile}

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/fb957c4ec07981d0. Report an issue: GitHub.