MuntashirAkon/AppManager · error · IllegalArgumentException

Block size must be a multiple of 512 bytes. Attempt to use s

Error message

Block size must be a multiple of 512 bytes. Attempt to use set size of ${blockSize}

What it means

TarArchiveOutputStream requires the block size to be a positive multiple of the 512-byte tar record size. A non-positive or non-multiple value is rejected with an IllegalArgumentException before any output is written.

Source

Thrown at app/src/main/java/org/apache/commons/compress/archivers/tar/TarArchiveOutputStream.java:204

    /**
     * Constructor for TarArchiveOutputStream.
     *
     * @param os the output stream to use
     * @param blockSize the block size to use. Must be a multiple of 512 bytes.
     * @param encoding name of the encoding to use for file names
     * @since 1.4
     */
    public TarArchiveOutputStream(final OutputStream os, final int blockSize,
        final String encoding) {
        final int realBlockSize;
        if (BLOCK_SIZE_UNSPECIFIED == blockSize) {
            realBlockSize = RECORD_SIZE;
        } else {
            realBlockSize = blockSize;
        }

        if (realBlockSize <=0 || realBlockSize % RECORD_SIZE != 0) {
            throw new IllegalArgumentException("Block size must be a multiple of 512 bytes. Attempt to use set size of " + blockSize);
        }
        out = new FixedLengthBlockOutputStream(countingOut = new CountingOutputStream(os),
                                               RECORD_SIZE);
        this.encoding = encoding;
        this.zipEncoding = ZipEncodingHelper.getZipEncoding(encoding);

        this.recordBuf = new byte[RECORD_SIZE];
        this.recordsPerBlock = realBlockSize / RECORD_SIZE;
    }

    /**
     * Set the long file mode. This can be LONGFILE_ERROR(0), LONGFILE_TRUNCATE(1) or
     * LONGFILE_GNU(2). This specifies the treatment of long file names (names &gt;=
     * TarConstants.NAMELEN). Default is LONGFILE_ERROR.
     *
     * @param longFileMode the mode to use
     */
    public void setLongFileMode(final int longFileMode) {

View on GitHub (pinned to 0152f468fc)

Solutions

1. Use a blockSize that is a positive multiple of 512 (512, 1024, 10240 are common).
2. Omit the blockSize parameter and use a constructor default.
3. Validate any user/config-supplied block size with blockSize > 0 && blockSize % 512 == 0 before constructing the stream.

Example fix

// before
new TarArchiveOutputStream(out, 1000, "UTF-8"); // throws
// after
int blockSize = 10240; // multiple of 512
new TarArchiveOutputStream(out, blockSize, "UTF-8");

if (blockSize <= 0 || blockSize % 512 != 0) throw new IllegalArgumentException("blockSize must be a positive multiple of 512");

try {
    os = new TarArchiveOutputStream(out, cfg.getBlockSize(), enc);
} catch (IllegalArgumentException e) {
    os = new TarArchiveOutputStream(out, 10240, enc); // safe default
}

When it happens

Trigger: Constructing TarArchiveOutputStream with blockSize <= 0 or blockSize % 512 != 0, e.g. blockSize=1000 or 0 (values below 512 are clamped to 512, but 513..1023 fail).

Common situations: Using block sizes copied from other archive tools (e.g. 10240 is fine, 8192 is not since 8192 is a multiple — 4096 is not? it is not: 4096/512=8, so fine; typical failures are odd sizes like 1KB+512 offsets or 0/negative values from config files).

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Tar record size must always be 512 bytes. Attempt to set siz
• blockSize(" + blockSize + ") < 1
• The app has keystore items and KeyStore backup isn't enabled
• APK files backup is requested but no source directory has be
• Failed to backup data directory at

AI-assisted analysis of MuntashirAkon/AppManager@0152f468fc (2026-09-12). Data as JSON: /api/errors/df9c0f9afb7eb6ba. Report an issue: GitHub.