Originally built to expose process and kernel internals as virtual files. Still useful for read-mostly system information, but the kernel community considers it a poor fit for new driver interfaces — sysfs is the recommended replacement for anything driver-related, and most actively maintained drivers avoid adding new procfs entries.

The official, formally documented ABI for exposing device and driver attributes to user space. Each attribute is typically a small, single-value file, tied directly into the kernel’s device model. Tools like udev depend heavily on sysfs, which is one reason it’s treated as a stable, production-grade contract with user space.

An intentionally unconstrained filesystem for exposing whatever internal state is useful during development or field debugging, with no ABI stability guarantees. On current kernels, access to debugfs can be restricted at boot or disabled entirely, and mainline kernels increasingly gate parts of it behind the kernel lockdown feature when Secure Boot is active.

A socket-based, message-oriented interface used extensively by core networking code, udev, and any subsystem that needs asynchronous, multicast-capable communication with multiple user space listeners at once. Modern kernels favor Generic Netlink for new subsystems, since it avoids the need to allocate a fixed protocol number for every new use case.

A direct, synchronous command channel tied to an open file descriptor. It remains the standard mechanism for structured, multi-parameter control operations in subsystems such as V4L2 and DRM, and in the vast majority of vendor character drivers, precisely because it doesn’t require the caller to parse text or manage a socket.

For most simple attributes, sysfs. For structured control commands, ioctl. Reach for netlink or debugfs only when their specific strengths — async multicast messaging or unconstrained debug access — are actually needed.

Not entirely — it’s still used for legacy process and system-wide information — but it is discouraged for any new driver-specific interface in favor of sysfs.

No. debugfs carries no ABI stability guarantee and can be disabled or restricted, especially under kernel lockdown, so production-critical functionality should not depend on it.

Netlink supports asynchronous, multicast-style delivery to multiple listeners at once, which fits networking’s event-driven nature far better than a synchronous, single-caller ioctl.

It’s a Linux Security Module that restricts operations — including certain debugfs and ioctl paths — that could let user space modify running kernel code or memory, typically enabled alongside Secure Boot.

Generally yes, since each ioctl command needs careful encoding, validation, and often 32/64-bit compatibility handling, whereas a sysfs attribute is a simple, self-documenting file.