About FreeBSD's Technological Advances
FreeBSD offers many advanced features.
No matter what the application, you want your system's resources performing
at their full potential. FreeBSD's advanced features enable you to do just
A complete operating system based on 4.4BSD.
FreeBSD's distinguished roots derive from the latest BSD software
releases from the Computer Systems Research Group at the University of California,
Berkeley. The book The Design and Implementation of 4.4BSD Operating System ,
written by the 4.4BSD system architects, thus describes much of FreeBSD's core
functionality in detail.
Drawing on the skills and experience of a diverse and world-wide group of
volunteer developers, the FreeBSD Project has worked to extend the feature
set of the 4.4BSD operating system in many ways, striving constantly to make
each new release of the OS more stable, faster and containing new functionality
driven by user requests.
FreeBSD provides higher performance, greater compatibility with other operating
systems and less system administration.
FreeBSD's developers attacked some of the more difficult problems in operating
systems design to give you these advanced features:
FreeBSD provides many security features to protect networks and servers.
- A merged virtual memory and filesystem buffer cache continuously
tunes the amount of memory used for programs and the disk cache. As a result,
programs receive both excellent memory management and high performance disk
access, and the system administrator is freed from the task of tuning cache
- Compatibility modules enable programs for other operating
systems to run on FreeBSD, including programs for Linux, SCO UNIX, and System
V Release 4.
- Soft Updates allows improved filesystem performance without
sacrificing safety and reliability. It analyzes meta-data filesystem operations
to avoid having to perform all of those operations synchronously. Instead,
it maintains internal state about pending meta-data operations and uses this
information to cache meta-data, rewrite meta-data operations to combine subsequent
operations on the same files, and reorder meta-data operations so that they
may be processed more efficiently. Features such as background filesystem
checking and file system snapshots are built on the consistency and performance
foundations of soft updates.
- File system snapshots , permitting administrators to take
atomic file system snapshots for backup purposes using the free space in
the file system, as well as facilitating background fsck ,
which allows the system to reach multiuser mode without waiting on file system
cleanup operations following power outages.
- Support for IP Security (IPsec) allows improved security
in networks, and support for the next-generation Internet Protocol, IPv6.
The FreeBSD IPsec implementation includes support for a broad range of accelerated
crypto hardware .
- Out of the box support for IPv6 via the KAME IPv6 stack
allows FreeBSD to be seamlessly integrated into next generation networking
environments. FreeBSD even ships with many applications extended to support
- Multi-threaded SMP architecture capable of executing
the kernel in parallel on multiple processors, and with kernel preemption ,
allowing high priority kernel tasks to preempt other kernel activity, reducing
latency. This includes a multi-threaded network stack and
a multi-threaded virtual memory subsystem . With FreeBSD
6.x, support for a fully parallel VFS allows the UFS file system to run on
multiple processors simultaneously, permitting load sharing of CPU-intensive
- M:N application threading via pthreads permitting threads
to execute on multiple CPUs in a scaleable manner, mapping many user threads
onto a small number of Kernel Schedulable Entities . By
adopting the Scheduler Activation model, the threading
approach can be adapted to the specific requirements of a broad range of
- Netgraph pluggable network stack allows developers to
dynamically and easily extend the network stack through clean layered network
abstractions. Netgraph nodes can implement a broad range of new network services,
including encapsulation, tunneling, encryption, and performance adaptation.
As a result, rapid prototyping and production deployment of enhanced network
services can be performed far more easily and with fewer bugs.
- TrustedBSD MAC Framework extensible kernel security ,
which allows developers to customize the operating system security model
for specific environments, from creating hardening policies to deploying
mandatory labeled confidentiality of integrity policies. Sample seucrity
policies include Multi-Level Security (MLS) , and Biba
Integrity Protection . Third party modules include SEBSD ,
a FLASK-based implementation of Type Enforcement .
- GEOM pluggable storage layer , which permits new storage
services to be quickly developed and cleanly integrated into the FreeBSD
storage subsystem. GEOM provides a consistent and coherent model for discovering
and layering storage services, making it possible to layer services such
as RAID and volume management easily.
- FreeBSD's GEOM-Based Disk Encryption (GBDE) , provides
strong cryptographic protection using the GEOM Framework, and can protect
file systems, swap devices, and other use of storage media.
- Kernel Queues allow programs to respond more efficiently
to a variety of asynchronous events including file and socket IO, improving
application and system performance.
- Accept Filters allow connection-intensive applications,
such as web servers, to cleanly push part of their functionality into the
operating system kernel, improving performance.
The FreeBSD developers are as concerned about security as they are about performance
and stability. FreeBSD includes kernel support for stateful IP firewalling ,
as well as other services, such as IP proxy gateways , access
control lists , mandatory access control , jail-based
virtual hosting , and cryptographically protected storage .
These features can be used to support highly secure hosting of mutually untrusting
customers or consumers, the strong partitioning of network segments, and the
construction of secure pipelines for information scrubbing and information
FreeBSD also includes support for encryption software, secure shells, Kerberos
authentication, "virtual servers" created using jails, chroot-ing services
to restrict application access to the file system, Secure RPC facilities, and
access lists for services that support TCP wrappers.