diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/boot-config.nix b/pkgs/os-specific/bsd/openbsd/pkgs/boot-config.nix
new file mode 100644
index 000000000000..23bd63e6d1ac
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/boot-config.nix
@@ -0,0 +1,32 @@
+{
+  mkDerivation,
+  lib,
+  flex,
+  byacc,
+  compatHook,
+}:
+mkDerivation {
+  path = "usr.sbin/config";
+
+  extraNativeBuildInputs = [
+    flex
+    byacc
+    compatHook
+  ];
+
+  postPatch = ''
+    rm $BSDSRCDIR/usr.sbin/config/ukc.c
+    rm $BSDSRCDIR/usr.sbin/config/ukcutil.c
+    rm $BSDSRCDIR/usr.sbin/config/cmd.c
+    rm $BSDSRCDIR/usr.sbin/config/exec_elf.c
+  '';
+
+  buildPhase = ''
+    for f in *.l; do flex $f; done
+    for f in *.y; do yacc -H ''${f%.y}.h $f; done
+    for f in *.c; do $CC -I$TMP/include -DMAKE_BOOTSTRAP -c $f; done
+    $CC *.o -o config
+  '';
+
+  meta.platforms = lib.platforms.linux;
+}
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/boot-ctags.nix b/pkgs/os-specific/bsd/openbsd/pkgs/boot-ctags.nix
new file mode 100644
index 000000000000..e4bf4607da47
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/boot-ctags.nix
@@ -0,0 +1,25 @@
+{
+  mkDerivation,
+  lib,
+  flex,
+  byacc,
+  compatHook,
+}:
+mkDerivation {
+  path = "usr.bin/ctags";
+
+  extraNativeBuildInputs = [
+    flex
+    byacc
+    compatHook
+  ];
+
+  buildPhase = ''
+    for f in *.l; do flex $f; done
+    for f in *.y; do yacc -H ''${f%.y}.h $f; done
+    for f in *.c; do $CC -I$TMP/include -DMAKE_BOOTSTRAP -c $f; done
+    $CC *.o -o ctags
+  '';
+
+  meta.platforms = lib.platforms.linux;
+}
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/err.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/err.h
new file mode 100644
index 000000000000..8ff38a621743
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/err.h
@@ -0,0 +1,30 @@
+#pragma once
+#include_next <err.h>
+
+#include <errno.h>
+#include <stdarg.h>
+static inline void __attribute__((__format__(printf, 3, 4)))
+errc(int eval, int code, const char *fmt, ...) {
+  // verr uses the error code from errno
+  // No need to keep the old value since this is noreturn anyway
+  errno = code;
+
+  va_list args;
+  va_start(args, fmt);
+  verr(eval, fmt, args);
+  va_end(args);
+}
+
+static inline void __attribute__((__format__(printf, 2, 3)))
+warnc(int code, const char *fmt, ...) {
+  // verr uses the error code from errno
+  int old_errno = errno;
+  errno = code;
+
+  va_list args;
+  va_start(args, fmt);
+  vwarn(fmt, args);
+  va_end(args);
+
+  errno = old_errno;
+}
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/fcntl.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/fcntl.h
new file mode 100644
index 000000000000..d8bb61a2291d
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/fcntl.h
@@ -0,0 +1,6 @@
+#pragma once
+#include_next <fcntl.h>
+
+// Linux doesn't let you lock during open, make these do nothing
+#define O_EXLOCK 0
+#define O_SHLOCK 0
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/cdefs.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/cdefs.h
new file mode 100644
index 000000000000..ea433160ad7c
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/cdefs.h
@@ -0,0 +1,4 @@
+#include_next <sys/cdefs.h>
+
+#define __packed __attribute__((__packed__))
+#define __aligned(x) __attribute__((__aligned__(x)))
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/dirent.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/dirent.h
new file mode 100644
index 000000000000..d66bbdf7b613
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/dirent.h
@@ -0,0 +1 @@
+#include <dirent.h>
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/endian.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/endian.h
new file mode 100644
index 000000000000..9abc15484c51
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/endian.h
@@ -0,0 +1,2 @@
+// Seems to be the only header for htonl
+#include <netinet/in.h>
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/types.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/types.h
new file mode 100644
index 000000000000..dc2578a8a1bb
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/sys/types.h
@@ -0,0 +1,10 @@
+#include_next <sys/types.h>
+
+// for makedev, major, minor
+#include <sys/sysmacros.h>
+
+// For htonl, htons, etc.
+#include <arpa/inet.h>
+
+// for uint32_t etc.
+#include <stdint.h>
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/unistd.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/unistd.h
new file mode 100644
index 000000000000..a52d202801f9
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/unistd.h
@@ -0,0 +1,8 @@
+#pragma once
+
+#include_next <unistd.h>
+
+// Reimplementing pledge and unvail with seccomp would be a pain,
+// so do nothing but claim they succeeded
+static int pledge(const char *, const char *) { return 0; }
+static int unveil(const char *, const char *) { return 0; }
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/util.h b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/util.h
new file mode 100644
index 000000000000..a12c43b15a9e
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/include/util.h
@@ -0,0 +1 @@
+#include <sys/types.h>
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compat/package.nix b/pkgs/os-specific/bsd/openbsd/pkgs/compat/package.nix
new file mode 100644
index 000000000000..69d457a180d8
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compat/package.nix
@@ -0,0 +1,16 @@
+{ runCommand, lib }:
+
+runCommand "openbsd-compat"
+  {
+    include = ./include;
+
+    meta = with lib; {
+      description = "A header-only library for running OpenBSD software on Linux";
+      platforms = lib.platforms.linux;
+      maintainers = with lib.maintainers; [ artemist ];
+    };
+  }
+  ''
+    mkdir -p $out
+    cp -R $include $out/include
+  ''
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compatHook/package.nix b/pkgs/os-specific/bsd/openbsd/pkgs/compatHook/package.nix
new file mode 100644
index 000000000000..3678b60f658b
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compatHook/package.nix
@@ -0,0 +1,13 @@
+{
+  stdenv,
+  makeSetupHook,
+  compat,
+}:
+
+makeSetupHook {
+  name = "openbsd-compat-hook";
+  substitutions = {
+    inherit compat;
+    inherit (stdenv.cc) suffixSalt;
+  };
+} ./setup-hook.sh
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/compatHook/setup-hook.sh b/pkgs/os-specific/bsd/openbsd/pkgs/compatHook/setup-hook.sh
new file mode 100644
index 000000000000..af70cb4bcc8a
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/compatHook/setup-hook.sh
@@ -0,0 +1,5 @@
+useOpenBSDCompat () {
+  export NIX_CFLAGS_COMPILE_@suffixSalt@+="-I@compat@/include"
+}
+
+postHooks+=(useOpenBSDCompat)
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/make-rules/package.nix b/pkgs/os-specific/bsd/openbsd/pkgs/make-rules/package.nix
index a16448752566..7e8a36ada14b 100644
--- a/pkgs/os-specific/bsd/openbsd/pkgs/make-rules/package.nix
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/make-rules/package.nix
@@ -34,6 +34,8 @@ mkDerivation {
     sed -i -E \
       -e 's|/usr/lib|\$\{LIBDIR\}|' \
       share/mk/bsd.prog.mk
+
+    substituteInPlace share/mk/bsd.obj.mk --replace-fail /bin/pwd pwd
   '';
 
   installPhase = ''
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/mkDerivation.nix b/pkgs/os-specific/bsd/openbsd/pkgs/mkDerivation.nix
index 44709f680884..0e0778d394a6 100644
--- a/pkgs/os-specific/bsd/openbsd/pkgs/mkDerivation.nix
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/mkDerivation.nix
@@ -53,7 +53,7 @@ lib.makeOverridable (
         install
         tsort
         lorder
-      ];
+      ] ++ (attrs.extraNativeBuildInputs or [ ]);
 
       HOST_SH = stdenv'.shell;
 
@@ -93,6 +93,6 @@ lib.makeOverridable (
       dontBuild = true;
     }
     // lib.optionalAttrs stdenv'.hostPlatform.isStatic { NOLIBSHARED = true; }
-    // attrs
+    // (builtins.removeAttrs attrs [ "extraNativeBuildInputs" ])
   )
 )
diff --git a/pkgs/os-specific/bsd/openbsd/pkgs/sys.nix b/pkgs/os-specific/bsd/openbsd/pkgs/sys.nix
new file mode 100644
index 000000000000..58f1a0be8430
--- /dev/null
+++ b/pkgs/os-specific/bsd/openbsd/pkgs/sys.nix
@@ -0,0 +1,66 @@
+{
+  mkDerivation,
+  boot-config,
+  pkgsBuildTarget,
+  baseConfig ? "GENERIC",
+}:
+mkDerivation {
+  path = "sys/arch/amd64";
+  pname = "sys";
+  extraPaths = [ "sys" ];
+  noLibc = true;
+
+  extraNativeBuildInputs = [
+    boot-config
+  ];
+
+  postPatch =
+    # The in-kernel debugger (DDB) requires compiler flags not supported by clang, disable it
+    ''
+      sed -E -i -e '/DDB/d' $BSDSRCDIR/sys/conf/GENERIC
+      sed -E -i -e '/pseudo-device\tdt/d' $BSDSRCDIR/sys/arch/amd64/conf/GENERIC
+    ''
+    +
+      # Clang flags compatibility
+      ''
+        find $BSDSRCDIR -name 'Makefile*' -exec sed -E -i -e 's/-fno-ret-protector/-fno-stack-protector/g' -e 's/-nopie/-no-pie/g' {} +
+        sed -E -i -e 's_^\tinstall.*$_\tinstall bsd ''${out}/bsd_' -e s/update-link// $BSDSRCDIR/sys/arch/*/conf/Makefile.*
+      ''
+    +
+      # Remove randomness in build
+      ''
+        sed -E -i -e 's/^PAGE_SIZE=.*$/PAGE_SIZE=4096/g' -e '/^random_uniform/a echo 0; return 0;' $BSDSRCDIR/sys/conf/makegap.sh
+        sed -E -i -e 's/^v=.*$/v=0 u=nixpkgs h=nixpkgs t=`date -d @1`/g' $BSDSRCDIR/sys/conf/newvers.sh
+      '';
+
+  postConfigure = ''
+    export BSDOBJDIR=$TMP/obj
+    mkdir $BSDOBJDIR
+    make obj
+
+    cd conf
+    config ${baseConfig}
+    cd -
+  '';
+
+  preBuild =
+    # A lot of files insist on calling unprefixed GNU `ld` and `objdump`.
+    # It's easier to add them to PATH than patch and substitute.
+    ''
+      mkdir $TMP/bin
+      export PATH=$TMP/bin:$PATH
+      ln -s ${pkgsBuildTarget.binutils}/bin/${pkgsBuildTarget.binutils.targetPrefix}objdump $TMP/bin/objdump
+      ln -s ${pkgsBuildTarget.binutils}/bin/${pkgsBuildTarget.binutils.targetPrefix}ld $TMP/bin/ld
+    ''
+    +
+      # The Makefile claims it needs includes, but it really doesn't.
+      # Tell it includes aren't real and can't hurt it.
+      ''
+        cd compile/${baseConfig}/obj
+        echo 'includes:' >>Makefile
+      '';
+
+  # stand is in a separate package
+  env.SKIPDIR = "stand";
+  env.NIX_CFLAGS_COMPILE = "-Wno-unused-command-line-argument -Wno-visibility";
+}