The HDFS snapshot/restore plugin is built against the latest Apache Hadoop 2.x (currently 2.7.1). If the distro you are using is not protocol compatible with Apache Hadoop, consider replacing the Hadoop libraries inside the plugin folder with your own (you might have to adjust the security permissions required).
Even if Hadoop is already installed on the Elasticsearch nodes, for security reasons, the required libraries need to be placed under the plugin folder. Note that in most cases, if the distro is compatible, one simply needs to configure the repository with the appropriate Hadoop configuration files (see below).
- Windows Users
Using Apache Hadoop on Windows is problematic and thus it is not recommended. For those really wanting to use it, make sure you place the elusive
winutils.exeunder the plugin folder and point
HADOOP_HOMEvariable to it; this should minimize the amount of permissions Hadoop requires (though one would still have to add some more).