System security is mostly related to the Operating System (OS) security and remote Secure Shell (SSH) access to nodes. OS security consists of regular checking and resolution of OS security vulnerability by applying patches or workarounds. As an administrator, you need to be aware of OS vulnerabilities and new malware that's released by hackers. You should also be aware of the different security patches and workarounds for those vulnerabilities.
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A Hadoop cluster consists of a variety of nodes with different profiles. Some are master nodes consisting of NameNodes and journal nodes. Some are worker nodes consisting of HDFS DataNodes and HBase region servers. Especially in the case of remote SSH access, your firewall rules may also vary as per profile...
