NetBSD 3.1

NetBSD is a free, secure, and highly portable Unix-like Open Source operating system available for many platforms, from 64-bit Opteron machines and desktop systems to handheld and embedded devices.
Its clean design and advanced features make it excellent in both production and research environments, and it is user-supported with complete source. Many applications are easily available through The NetBSD Packages Collection.
Main features:
- Clean design
- Wide platform support
- BSD License
- Full source availability
- Security
- Mature and stable
- Hype free
- Packet filtering and Network Address Translation (NAT)
- IPv6
- Network File System (NFS)
- Comprehensive and robust networking
- Wireless networking
- Hardware and software RAID
- High performance PCI IDE
- SCSIPI subsystem - combined SCSI and ATAPI
- 64-bit filesystems
- Large IDE disks
- Soft Updates on FFS for high performance and reliability
- Many filesystem types
- DVD ROM and RAM
- The package system (applications)
- Machine independent driver framework
- Machine independent audio framework
- Kernel debugging
- OS emulation
- USB (Universal serial bus)
- Other device support
- The UVM virtual memory system
- Cardbus
- wscons machine independent console
- 64-bit clean
- Non-executable stack and heap