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Pseudo-Devices

These are things that act like hardware, but have no actual hardware attached. Most are found on all architectures. If a number appears after a pseudo-device driver, that is the total number of the particular pseudo-device driver the system will support.

Disk-Like Pseudo-Devices

This is a disk-like interface to files, for a variety of filesystem tricks. See Chapter 15.

This allows you to combine multiple disks into one large concatenated disk. See ccd(4).

This is the RAIDframe software RAID system. See raid(4).

Networking Pseudo-Devices

These pseudo-devices provide different methods of accessing the network.

This is OpenBSD's integrated packet filter, and is discussed in Chapters 17 through 19.

This device lets pf log what it does, and is also discussed in Chapters 17 through 19.

This is the loopback device. If you remove it, many programs will break in an entertaining way. See lo(4) for details.

This supports the Berkeley Packet Filter, the standard packet sniffer.

This supports SLIP, the popular pre-PPP dialup protocol.

This lets you connect to the Internet with dialup connections using pppd(8). I recommend using user-mode ppp, which requires tun devices instead of this. See Chapter 9.

This supports Synchronous PPP. Most people have no need of it, but see sppp(4) if you're curious.

This is a tunneling network device, used by user-mode ppp and a variety of VPN tools. We discuss using tun with ppp in Chapter 9.

man: brconfig(8)

Bridging is where two separate Ethernet segments are connected transparently.

This lets you divide a single Ethernet into two segments, or virtual lans. See vlan(4).

This supports Cisco Generic Routing Encapsulation, a common VPN protocol. See gre(4).

Pseudo-terminals are software terminals. Every remote shell connection needs a pseudo-terminal. See pty(4).

This supports many popular serial digitizers. See tb(4).

This lets a programmer pull symbol names from a running kernel. It's very useful for kernel developers; see ksyms(4).

IPv6 Pseudo-Devices

While we're not covering IPv6 in this book, the following IPv6 devices are included in the GENERIC kernel and so should be mentioned.

This is a generic IP tunnel, allowing you to tunnel either IPv4 or IPv6 over IPv4 or IPv6. See gif(4).

This pseudo-device can capture IPv6 traffic and relay it to a userland program. See faith(4).

The encapsulation interface allows the system to send IPv6 traffic through pf(4). See enc(4).

Miscellaneous Pseudo-Devices

The following pseudo-devices really don't fit anywhere else.

This adds hooks for performance counters, discussed in pctr(1).

This pseudo-device provides access to the memory range attributes supported on Pentium CPUs. See mtrr(4).

This supports MIDI sequencers.

This is a virtual multiplexor for the wscons virtual console framework.

This provides userland programs a generic interface to hardware cryptographic support through the kernel. See crypto(4).