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AIX Concepts

Core Concepts, Administration, and Roadmap

Introduction to AIX

AIX (Advanced Interactive eXecutive) is a specialized UNIX operating system that stands out due to its reliance on a proprietary internal database, the Object Data Manager (ODM), which stores critical configuration data for the Logical Volume Manager (LVM) and system devices. For administrative tasks, the use of SMITTY (System Management Interface Tool) is highly recommended, as it simplifies complex commands and helps prevent common administrative errors.

Logical Volume Manager (LVM)

AIX's LVM virtualizes physical disks, offering a flexible and robust storage management system:

  • Physical Volumes (PVs): The underlying physical hard disks. Commands like lspv list available PVs.
  • Volume Groups (VGs): Containers for PVs, with the mandatory rootvg being the core system volume group. VGs are partitioned into Physical Partitions (PPs), which are the smallest allocation unit for Logical Volumes. VGs have maximum capacity limits based on the PP size (e.g., 1016 PPs per PV for a standard VG, which can be modified using the chvg -t command).
  • Logical Volumes (LVs): Data containers within a VG used for RAW devices or filesystems. While LVs can be directly resized, it is generally recommended to change the filesystem size (chfs), which automatically adjusts the underlying LV.
  • Mirroring and Resilience: AIX LVM supports RAID 0, 1, and 0+1 (10). Mirroring can be configured at the LV level (mklvcopy) or across the entire VG (mirrorvg). Special procedures (bosboot and bootlist) are required to ensure a mirrored rootvg is fully bootable.
  • VG Operations: VGs (excluding rootvg) can be taken offline (varyoffvg), brought online (varyonvg), and even exported and imported (the only way to effectively rename a VG).
  • Snapshots: Snapshots are often created by splitting a mirror copy (splitvg) to get an instantaneous, full copy of the data, which can be mounted read-only for backup purposes. JFS2 filesystems also support their own snapshot mechanism.

Filesystem Management and Networking

AIX filesystems include JFS and the modern JFS2 (Enhanced Journaled File System). Filesystem configurations are tracked in /etc/filesystems.

  • Resizing: Filesystem size is adjusted using chfs -a size=<new_size>.
  • NFS (Network File System): NFS exports are configured in /etc/exports and managed via exportfs -va. When mounting an NFS share, using the soft option is preferred over the default hard mount to prevent the system from freezing due to network issues.
  • JFS2 Snapshots: Instantaneous, read-only copies. Multiple snapshots can be chained, meaning the most recent snapshot depends on the previous ones.

Device and Package Administration

  • Device Management: All devices are defined in the ODM. Commands like lsdev -C list all configured devices (disks, adapters, etc.), and lsslot shows their physical locations. lscfg -vp provides detailed hardware characteristics (serial number, firmware, etc.).
  • Package Management: AIX software is managed through a hierarchy:
    • Filesets: The basic unit of software/patching.
    • APARs (Authorized Program Analysis Report): Individual fixes.
    • Service Packs (SPs): Intermediate updates for critical and security fixes (oslevel -s).
    • Technology Levels (TLs): Major, stable updates released twice a year with new features and hardware support (oslevel -r).
  • Updating: Updates are managed via smitty update_all. Patches can be temporarily APPLIED (allowing for simple rollback) or COMMITTED (finalized).

Backup and Daemon Management

  • System Backup: The mksysb command performs a unique system backup that includes a boot image (bosboot), system definition files (image.data and bosinst.data), and the system data. Backups created on CD/DVD/tape are bootable, while file-based backups are not.
  • Daemons: System daemons are managed via the System Resource Controller (SRC), using commands like lssrc -a to list all services and startsrc/stopsrc for control.

AIX Roadmap and Modernization (AIX 7.3 TL2 Highlights)

IBM’s roadmap for AIX is focused on Hybrid Cloud enablement and system modernization. The AIX 7.3 Technology Level 2 (TL2), released in November 2023, highlights these key areas:

Automation and Modernization

  • Open-Source Integration: Focus on integrating open-source technology for easier management and cloud deployment models.
  • Core Tools Updates: Inclusion of updated open-source components:
    • Python (v3.19.17) for out-of-the-box Ansible automation.
    • Bash (v5.2.15) as an included alternate shell.
    • Updates to essential libraries and tools (libxml2, rpm, rsyslog).
  • Management Enhancements: Improved capabilities for image creation, such as create_ova with hardware compression.

Enhanced Availability

  • Live Kernel Update: Optimized performance for AIX live kernel updates in PowerVC environments.
  • Network Resilience: Enhanced LLDP (Link Layer Discovery Protocol) reporting.
  • Storage Resilience: MPIO (Multipath I/O) support for FPIN (Fabric Performance Impact Notification).