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illumos provides a number of advanced features for downstream distributions and users to utilize.


The illumos project is part of the community of operating system projects that ships OpenZFS.

ZFS provides excellent data integrity, performance, flexibility and ease-of-use you simply can't find in other file systems. ZFS combines traditional concepts like volume management, and file systems with a pooled storage that does for disks what virtual memory did for RAM.

ZFS was developed at Sun Microsystems in the early 2000s and released as open source in 2005 as part of the OpenSolaris project. OpenZFS was announced in 2013. For a more detailed history, please see OpenZFS History.

ZFS allows you to:

  • Group devices into a single storage pool with various redundancy characteristics
  • Create tiered storage with log and cache devices
  • Create read-only atomic file system snapshots
  • Create writable clones of snapshots
  • Send snapshots as a byte stream -- which you can redirect to a file, or send across the network!
  • Dynamically modify dataset (file system) attributes
  • Delegate dataset management to non-root users or groups

ZFS includes online checksumming of every block, on-demand scrubbing of disks, and -- in redundant configurations -- self-healing of bad data with good.

ZFS has been ported to Linux, FreeBSD, OS X -- and a Windows port is in progress as of late 2017!


illumos includes a number of virtualization technologies, including:

  • Zones, a light weight operating system-level virtualization; analogous to "jails" or "containers" as provided by other systems
  • Hardware virtualization

Native Zones

Native zones provide an isolated illumos environment to run your applications in, like having a virtual machine without the hypervisor overhead.

LX (Linux Emulation)

LX-branded zones provide the Linux system call interface, allowing you to run most Linux application binaries without recompiling them for illumos. This facility is available in several illumos distributions, including SmartOS and OmniOS.


KVM and QEMU were ported to illumos in 2011, and can be used on Intel CPUs with VMX and EPT support.


Joyent is in the process of porting the bhyve hypervisor from FreeBSD to illumos. The port is available in at least the SmartOS and OmniOS distributions.

Introspection and Debugging


DTrace allows for system-wide tracing of a kernel for debugging applications and the operating system, as well as gathering profiling data. DTrace along with MDB allows you to leverage CTF data to inspect userland and kernel structures.

Modular Debugger (MDB)

MDB, the illumos modular debugger, allows you to inspect running processes, core files, kernel state, and kernel crash dumps. KMDB also allows controlling the execution of a running kernel.

Service Management Facility (SMF)

SMF helps administrators manage services running on the system. SMF can take care of tracking service dependencies, supervising and restarting processes, disabling perpetually crashing applications, and more.


illumos uses ipfilter for firewalling. Using ipfilter you can create firewalls not just for the host system, but also for zones and hardware virtualized systems.

Virtual Networking

dladm(8) allows users to create Virtual NICs, bridges, and in some distributions overlay networks.