Differences from Linux to OpenBSD

There is a single filesystem rooted at '/', with entries like these:

/
|-- bin
|-- boot
|-- dev
|-- etc
|-- home
|-- lib
|-- mnt
|-- sbin
|-- tmp
|-- usr
|   |-- bin
|   |-- lib
|   `-- sbin
`-- var

Common user commands like ls, rm, grep, vi, and many more are the same, though sometimes with some different command-line options or a few different subcommands.

The X Window System is provided on both, including dbus. KDE, Gnome, XFCE4, or any other desktop layer can be used. Wayland is optional on OpenBSD.

Common programming languages like C and Perl are included if they are used to build part of the base system, and optional otherwise. The list of add-on programming languages is long and growing, including Ruby, Python, Java, Haskell, and many more.

Both systems are open-sourced (Most Linuxes allow "binary blob" driver code; OpenBSD does not, though it does provide open-source drivers for devices that need binary firmware, and provides a download mechanism fw_update).

OpenBSD runs most of the same thousands of open-source as you’d find on Linux (most via add-on packages).

OpenBSD runs on most of the same types of computer system as Linux: PC’s, laptops, Macs, Arm, RISC-V, and others, though often with fewer devices supported.

There is a single development team and a single distribution; the source trees contain everything that is in the base system. Source is available via CVS and mirrored on github; see "Getting Source" on main page. OpenBSD was the first major system to make its entire source code freely available over the internet via a revision control system.

The OpenBSD system is smaller, more coherent and cohesive.

As a result, many things that are "built in" to Linuxes are optional and can be installed by the user with pkg_add. This includes Emacs, the bash shell, CUPS printing, and more. Most users need only some of those things, so they are optional.

OpenBSD tends to adhere to the POSIX standard for Unix-like systems. Linux distros tend to adhere to LSB, the Linux Standards Base. The two specs overlap but have many differences.

OpenBSD uses the BSD or similar licenses for most of its built-in software; GPL’d software is usually made available in the add-on category.

OpenBSD puts almost all config files in /etc and all local software in /usr/local. There is no need to hunt through /usr/local, /opt/etc, /usr/local/opt/etc, or any other twisty little passages.

The OpenBSD man pages are superior to most systems, so there are no separate "info" or "doc" files for most of the base system. There is a very good FAQ, on the web site (link at left).

Linux has a dozen different tools for adding software, including rpm, apt, dnf, yam and deb. OpenBSD has one: pkg_add. OpenBSD package management does a really good job of handling dependencies and updates.

The system for building the add-on software is public: the ports tree. You can build any package from source code anytime you like, with one command.

Linux has taken the notion of 'processes as files' to a crazy degree; OpenBSD does not have a /proc or /system filesystem. It has traditional Unix/BSD tools for gathering the same information.

The sudo command has been replaced by the simpler doas command. If you can’t deal with that change, you can either install sudo from ports, or use a shell alias, which works for common cases.

Indeed, many of the "traditional system administration" commands are different, beyond the basics like ps, mount, netstat, and ifconfig (even the latter has disappeared from or been hidden by some Linuxes).

OpenBSD does not provide, and does not plan to provide, a GUI-based installer. The text-based installer is simple and works well.

mature OS, derived from 4BSD and hence V7, going back to 1970

relatively stable; system controlled by a small group with good taste

really good security: packet filtering; full code base audited

development of new security features such as pf, pledge, unveil, KARL and more, which are finding their way into other OSes

team also provides the standard ssh package used on most *nix system and even on MS-Windows

team also provides LibreSSL (cleaned-up OpenSSL), OpenBGP, OpenSMTPD (vastly more comprehensible than sendmail), and more

runs on most of the popular hardware platforms: amd64, i386, riscv64, arm64, and more

system largely compatible with traditional BSD UNIX (including SunOS)

large "ports tree" of software in source and pkg_add form

Almost all significant freeware and some commercialware available.

Quite a few newer hardware devices that Linux supports are not yet supported on OpenBSD

There is some software that just doesn’t work on OpenBSD. The ports team could use your help if your favorite tool isn’t ported yet!

Community can appear 'cold' to newcomers who either show up with bizarre suggestions and/or don’t read documentation before posting and/or who have entitlement issues (not sure this is actually a disadvantage; it may be a survival mechanism).