testcontainers/testcontainers-java · warning

Unable to read Dockerfile at path

Error message

Unable to read Dockerfile at path {}

What it means

ParsedDockerfile.read() calls Files.readAllLines on the Dockerfile; if reading throws IOException (e.g. permission problems, the file disappearing, or it is a directory), it logs this warning and returns an empty dependency list. The image build continues but dependency pre-pulling is skipped.

Solutions

1. Check filesystem permissions on the Dockerfile (chmod/chown) so the test JVM can read it
2. Confirm the path is a regular file, not a directory
3. Re-run the build; if a race with deletion, ensure nothing deletes the Dockerfile during the test

Example fix

// before
new ImageFromDockerfile().withDockerfile(Paths.get("/docker/dir"))
// after
Path p = Paths.get("/docker/Dockerfile");
if (!Files.isRegularFile(p) || !Files.isReadable(p)) throw new IllegalStateException("unreadable: " + p);
new ImageFromDockerfile().withDockerfile(p);

Path p = Paths.get(path);
if (!Files.isRegularFile(p) || !Files.isReadable(p)) {
    throw new IllegalStateException("Dockerfile unreadable: " + p);
}

try {
    Files.readAllLines(dockerfile);
} catch (IOException e) {
    throw new UncheckedIOException("Cannot read Dockerfile: " + dockerfile, e);
}

When it happens

Trigger: Files.readAllLines(dockerFilePath) throws IOException inside read(), called from the ParsedDockerfile constructor during ImageFromDockerfile.resolve().

Common situations: File deleted between exists() check and read (race); read permission denied; path is actually a directory; filesystem/I/O errors in CI containers with limited mounts.

Understand the failure class

Background: "failed to read file", EACCES, ENOENT and "could not read <path>" errors: when a program can't read a file from disk — this error's family across 49 libraries.

Related errors

• Tried to parse Dockerfile at path
• Could not load classpath init script
• Could not load classpath init script
• HTTP response code was
• Response: did not match predicate

AI-assisted analysis of testcontainers/testcontainers-java@8e549514e3 (2026-09-12). Data as JSON: /api/errors/fe38222b4abd00c0. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/testcontainers/images/ParsedDockerfile.java:54

        this.dependencyImageNames = parse(read());
    }

    @VisibleForTesting
    ParsedDockerfile(List<String> lines) {
        this.dockerFilePath = Paths.get("dummy.Dockerfile");
        this.dependencyImageNames = parse(lines);
    }

    private List<String> read() {
        if (!Files.exists(dockerFilePath)) {
            log.warn("Tried to parse Dockerfile at path {} but none was found", dockerFilePath);
            return Collections.emptyList();
        }

        try {
            return Files.readAllLines(dockerFilePath);
        } catch (IOException e) {
            log.warn("Unable to read Dockerfile at path {}", dockerFilePath, e);
            return Collections.emptyList();
        }
    }

    private Set<String> parse(List<String> lines) {
        Set<String> imageNames = lines
            .stream()
            .map(FROM_LINE_PATTERN::matcher)
            .filter(Matcher::matches)
            .map(matcher -> matcher.group("image"))
            .collect(Collectors.toSet());

        if (!imageNames.isEmpty()) {
            log.debug("Found dependency images in Dockerfile {}: {}", dockerFilePath, imageNames);
        }
        return imageNames;
    }
}

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