HP-UX (from "Hewlett Packard Unix") is Hewlett Packard Enterprise's proprietary implementation of the Unix operating system, based on Unix System V (initially System III) and first released in 1984. Current versions support HPE Integrity Servers, based on Intel's Itanium architecture. Earlier versions of HP-UX supported the HP Integral PC and HP 9000 Series 200, 300, and 400 computer systems based on the Motorola 68000 series of processors, the HP 9000 Series 500 computers based on HP's proprietary FOCUS architecture, and later HP 9000 Series models based on HP's PA-RISC instruction set architecture. HP-UX was the first Unix to offer access control lists for file access permissions as an alternative to the standard Unix permissions system. HP-UX was also among the first Unix systems to include a built-in logical volume manager. HP has had a long partnership with Veritas Software, and uses VxFS as the primary file system. It is one of four commercial operating systems that have versions certified to The Open Group's UNIX 03 standard. (The others are macOS, AIX and Huawei's EulerOS.) Characteristics HP-UX 11i offers a common shared disks for its clustered file system. HP Serviceguard is the cluster solution for HP-UX. HP Global Workload Management adjusts workloads to optimize performance, and integrates with Instant Capacity on Demand so installed resources can be paid for in 30-minute increments as needed for peak workload demands. HP-UX offers operating system-level virtualization features such as hardware partitions, isolated OS virtual partitions on cell-based servers, and HP Integrity Virtual Machines (HPVM) on all Integrity servers. HPVM supports guests running on HP-UX 11i v3 hosts – guests can run Linux, Windows Server, OpenVMS or HP-UX. HP supports online VM guest migration, where encryption can secure the guest contents during migration. HP-UX 11i v3 scales as follows (on a SuperDome 2 with 32 Intel Itanium 9560 processors): 256 processor cores 8 TB main memory 32 TB maximum file system 16 TB maximum file size 128 million ZB—16 million logical units each up to 8 ZB. Security The 11i v2 release introduced kernel-based intrusion detection, strong random number generation, stack buffer overflow protection, security partitioning, role-based access management, and various open-source security tools. HP classifies the operating system's security features into three categories: data, system and identity: Context dependent files Release 6.x (together with 3.x) introduced the context dependent files (CDF) feature, a method of allowing a fileserver to serve different configurations and binaries