apache/cassandra · error · RuntimeException

Unable to create directory:

Error message

Unable to create directory: 

What it means

Thrown when parsing the restore_directories property of commitlog_archiving.properties: a configured restore directory does not exist and Cassandra's attempt to create it (tryCreateDirectory) failed. Restore needs the directory present so archived segments can be copied into it.

Solutions

1. Create the restore directory manually with correct ownership: mkdir -p <dir> && chown cassandra:cassandra <dir>.
2. Verify each path in restore_directories does not point to an existing regular file.
3. Check the parent directory grants write permission to the Cassandra process.
4. Correct the path in commitlog_archiving.properties if it is a typo.

Example fix

# before
restore_directories: /nonexistent-readonly-mount/restore
# after
restore_directories: /var/lib/cassandra/commitlog_restore

for (String dir : restoreDirs.split(",")) {
    File d = new File(dir.trim());
    if (d.exists() && !d.isDirectory()) throw new IllegalStateException(dir + " is a file, not a directory");
    if (!d.exists() && !d.getParentFile().canWrite()) throw new IllegalStateException("cannot create " + dir);
}

try { new CommitLogArchiver(...); }
catch (RuntimeException e) {
    if (e.getMessage().startsWith("Unable to create directory")) provisionDir(e); 
    throw e;
}

When it happens

Trigger: CommitLogArchiver.getArchiverFromProperties(), called from construct(), when a path listed in restore_directories does not exist and mkdir fails (bad permissions, path is a file, unresolvable parent path).

Common situations: Typo in restore_directories path; parent directory missing so creation fails; path points to an existing regular file; Cassandra process lacks write permission on the parent; read-only mount in containers.

Understand the failure class

Background: mkdir permission denied (EACCES): failed to create directory errors explained — this error's family across 32 libraries.

Related errors

• commitlog_directory must not be the same as any…
• local_system_data_file_directory must not be the same as…
• NANOSECONDS level precision is not supported.
• Unable to determine block size for commit log directory
• Unable to list directory

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/8e21f30a29748647. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/commitlog/CommitLogArchiver.java:140

    }

    @VisibleForTesting
    static CommitLogArchiver getArchiverFromProperties(Properties commitlogCommands)
    {
        assert !commitlogCommands.isEmpty();
        String archiveCommand = commitlogCommands.getProperty("archive_command");
        String restoreCommand = commitlogCommands.getProperty("restore_command");
        String restoreDirectories = commitlogCommands.getProperty("restore_directories");
        if (restoreDirectories != null && !restoreDirectories.isEmpty())
        {
            for (String dir : restoreDirectories.split(DELIMITER))
            {
                File directory = new File(dir);
                if (!directory.exists())
                {
                    if (!directory.tryCreateDirectory())
                    {
                        throw new RuntimeException("Unable to create directory: " + dir);
                    }
                }
            }
        }

        String precisionPropertyValue = commitlogCommands.getProperty("precision", TimeUnit.MICROSECONDS.name());
        TimeUnit precision;
        try
        {
            precision = TimeUnit.valueOf(precisionPropertyValue);
        }
        catch (IllegalArgumentException ex)
        {
            throw new RuntimeException("Unable to parse precision of value " + precisionPropertyValue, ex);
        }
        if (precision == TimeUnit.NANOSECONDS)
            throw new RuntimeException("NANOSECONDS level precision is not supported.");

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