JNA temporary directory not mounted with noexec

Elasticsearch uses the Java Native Access (JNA) library for executing some platform-dependent native code. On Linux, the native code backing this library is extracted at runtime from the JNA archive. By default, this code is extracted to the Elasticsearch temporary directory which defaults to a sub-directory of /tmp. Alternatively, this location can be controlled with the JVM flag -Djna.tmpdir=<path>. As the native library is mapped into the JVM virtual address space as executable, the underlying mount point of the location that this code is extracted to must not be mounted with noexec as this prevents the JVM process from being able to map this code as executable. On some hardened Linux installations this is a default mount option for /tmp. One indication that the underlying mount is mounted with noexec is that at startup JNA will fail to load with a java.lang.UnsatisfiedLinkerError exception with a message along the lines of failed to map segment from shared object. Note that the exception message can differ amongst JVM versions. Additionally, the components of Elasticsearch that rely on execution of native code via JNA will fail with messages indicating that it is because JNA is not available. If you are seeing such error messages, you must remount the temporary directory used for JNA to not be mounted with noexec.