Restricting file permissions

Additional file protections are available on some file systems, including Windows NTFS, Unix, and Linux. You can configure Derby to take advantage of these extra file protections.

By default, Derby creates new directories and files with the default permissions of the operating system account that started the VM (the umask setting on Unix and Linux). You can configure Derby to override those default permissions and to restrict access to just that account. If you configure Derby this way, only that account can access the directories and files created by Derby. You can configure this extra protection by setting the following system property, either on the VM command line or in derby.properties:

derby.storage.useDefaultFilePermissions=false

For more information, see "derby.storage.useDefaultFilePermissions" in the Derby Reference Manual.

If you set this property, other operating system accounts will have no access to directories or files created by Derby. This behavior can be helpful in enhancing default security for database files.

The exact behavior is determined by two factors: how the Derby engine is started, and the presence or absence and specified value of the property derby.storage.useDefaultFilePermissions.

The following table shows how file access works. In this table,

• "Environment" means that access is controlled entirely by the JVM environment and the file location only (that is, by the umask setting on UNIX and Linux systems and by the default file permissions on Windows NTFS).
• "Restricted" means that Derby restricts access to the operating system account that started the JVM.

The following table shows how file access works with various settings of the derby.storage.useDefaultFilePermissions property.