diff --git a/CMakeLists.txt b/CMakeLists.txt
index f391940..8abe345 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,7 @@
 cmake_minimum_required(VERSION 3.9)
 project(dereko2vec VERSION 0.9.1 DESCRIPTION "Fork from wang2vec with extensions for re-training and count based models")
 option(STATIC_DEREKO2VEC "Build dereko2vec as a static binary" OFF)
+option(STATIC_ROCKSDB "Link rocksdb and collocatordb statically, everything else shared" OFF)
 if (STATIC_DEREKO2VEC AND APPLE)
     message(FATAL_ERROR "STATIC_DEREKO2VEC does not work on MacOS, which ships "
             "no static system libraries. Build without it.")
@@ -31,12 +32,14 @@
 include_directories(/usr/local/include /usr/local/kl/include /opt/homebrew/include)
 link_directories(/usr/local/kl/lib /usr/local/lib /usr/local/lib64 /opt/homebrew/lib)
 
-# A static dereko2vec needs everything as a static library. An ordinary build
-# takes the shared ones, and it has to take them explicitly: a leftover static
-# library below /usr/local would otherwise win over the shared library of the
-# distribution, because cmake weighs the search path higher than the suffix.
-# Set -DCOLLOCATORDB=<path> or -DROCKSDB=<path> to pick specific ones.
-if (STATIC_DEREKO2VEC)
+# A static dereko2vec needs everything as a static library. With STATIC_ROCKSDB
+# only rocksdb and collocatordb are static and the compression libraries stay
+# shared, which is the fast indexing build the README describes. An ordinary
+# build takes the shared ones, and it has to take them explicitly: a leftover
+# static library below /usr/local would otherwise win over the shared library
+# of the distribution, because cmake weighs the search path higher than the
+# suffix. Set -DCOLLOCATORDB=<path> or -DROCKSDB=<path> to pick specific ones.
+if (STATIC_DEREKO2VEC OR STATIC_ROCKSDB)
     find_library(COLLOCATORDB libcollocatordb_static.a)
     find_library(ROCKSDB librocksdb.a)
 else ()
@@ -50,16 +53,17 @@
 if (NOT COLLOCATORDB)
     message(FATAL_ERROR "No collocatordb found. Please install it from "
             "https://korap.ids-mannheim.de/gerrit/plugins/gitiles/ids-kl/collocatordb"
-            " - a static dereko2vec needs libcollocatordb_static.a, otherwise "
+            " - a static build needs libcollocatordb_static.a, otherwise "
             "libcollocatordb.so is enough.")
 endif ()
 if (NOT ROCKSDB)
     message(FATAL_ERROR "No rocksdb found. Install the rocksdb development "
             "package of your distribution, e.g. librocksdb-dev or "
-            "rocksdb-devel. Where there is none, or where it is older than the "
-            "one collocatordb was built against, build rocksdb and say where "
-            "it is: -DCMAKE_PREFIX_PATH=<prefix it was installed to>. It has "
-            "to be the same rocksdb that collocatordb was built against.")
+            "rocksdb-devel. Where there is none, or where a static one is "
+            "needed, scripts/build-rocksdb.sh builds one into a prefix of its "
+            "own; then say where it is: -DCMAKE_PREFIX_PATH=<prefix>. It has "
+            "to be the same rocksdb that collocatordb was built against, "
+            "which the script takes care of on its own.")
 endif ()
 message(STATUS "Using collocatordb ${COLLOCATORDB}")
 message(STATUS "Using RocksDB ${ROCKSDB}")
diff --git a/README.md b/README.md
index ff91da1..bf06a9f 100644
--- a/README.md
+++ b/README.md
@@ -4,21 +4,73 @@
 
 ## Installation
 
-### Dependencies
+### 1. Prerequisites
 
-* cmake
-* rocksdb. `librocksdb-dev` on Debian and Ubuntu and `rocksdb-devel` on Fedora
-  do. Rocky Linux and RHEL package a rocksdb that is too old, there it has to
-  be built, which the
-  [collocatordb README](https://korap.ids-mannheim.de/gerrit/plugins/gitiles/ids-kl/collocatordb)
-  describes
-* [libcollocatordb](https://korap.ids-mannheim.de/gerrit/plugins/gitiles/ids-kl/collocatordb) >= v1.6.0
+* on Fedora:
 
-It has to be the same rocksdb that collocatordb was built against. dereko2vec
-itself does not include any rocksdb header, but it links what collocatordb
-refers to, and symbols of one version do not exist in another.
+    ```bash
+    sudo dnf install cmake gcc-c++ git rocksdb-devel snappy-devel zlib-devel bzip2-devel lz4-devel libzstd-devel
+    ```
 
-### Build and install
+* on Rocky Linux 9 and 10 and RHEL: the same without `rocksdb-devel`, rocksdb
+  is built in the next step:
+
+    ```bash
+    sudo dnf install cmake gcc-c++ git snappy-devel zlib-devel bzip2-devel lz4-devel libzstd-devel
+    ```
+
+* on MacOS:
+
+    ```bash
+    brew install cmake rocksdb snappy zlib bzip2 lz4 zstd
+    ```
+
+### 2. RocksDB, where the static one is wanted or there is no package
+
+Linking rocksdb statically makes counting collocations about 22% faster -
+on an indexing run of two weeks that is about three days. Debian, Ubuntu and
+MacOS ship `librocksdb.a` in their rocksdb package, Fedora, Rocky Linux and
+RHEL do not. One script builds rocksdb once, with the shared and the static
+library, into a prefix of its own:
+
+```bash
+scripts/build-rocksdb.sh
+```
+
+It builds the version of the rocksdb package of the distribution where there
+is one, so that the static library matches the headers collocatordb is
+compiled against, and a pinned recent one where there is none (Rocky Linux,
+RHEL). The version and the prefix can be changed, see
+`scripts/build-rocksdb.sh --help`.
+
+On Rocky Linux and RHEL, which have no rocksdb package, this step is not
+optional, and programs that use the shared library need the prefix in the
+search path of the loader, which the script prints at its end.
+
+### 3. CollocatorDB
+
+[libcollocatordb](https://korap.ids-mannheim.de/gerrit/plugins/gitiles/ids-kl/collocatordb) >= v1.6.0:
+
+```bash
+git clone "https://korap.ids-mannheim.de/gerrit/ids-kl/collocatordb"
+cd collocatordb
+cmake -S . -B build -DCMAKE_INSTALL_PREFIX=/usr/local
+cmake --build build -j $(nproc)
+sudo cmake --install build && sudo ldconfig
+ctest --test-dir build --extra-verbose
+cd ..
+```
+
+Where rocksdb was built in step 2 and it is not the one of the distribution -
+on Rocky Linux and RHEL always, elsewhere when `-v` named another version -
+collocatordb has to be built against it, and naming its prefix covers the
+headers and both libraries at once:
+
+```bash
+cmake -S . -B build -DCMAKE_PREFIX_PATH=$HOME/rocksdb -DCMAKE_INSTALL_PREFIX=/usr/local
+```
+
+### 4. Build and install dereko2vec
 
 ```bash
 cmake -S . -B build
@@ -30,34 +82,30 @@
 This installs `dereko2vec` and `vecs2mmap`. The build directory has to be
 `build` inside the sources, the test looks for the binary relative to it.
 
-Where rocksdb or collocatordb were installed into a prefix of their own, name
-it, which covers the libraries and the header at once. Several prefixes are
-separated by semicolons:
+For the fast build with rocksdb and collocatordb linked statically, name the
+prefix of the rocksdb from step 2. The compression libraries stay shared:
+
+```bash
+cmake -S . -B build -DSTATIC_ROCKSDB=ON -DCMAKE_PREFIX_PATH=$HOME/rocksdb
+```
+
+On Debian, Ubuntu and MacOS, whose rocksdb package brings the static library,
+`-DSTATIC_ROCKSDB=ON` without a prefix does. And where rocksdb was installed
+into a prefix of its own but is to be linked shared, name it without the
+option:
 
 ```bash
 cmake -S . -B build -DCMAKE_PREFIX_PATH=$HOME/rocksdb
 ```
 
-### Faster indexing
+It has to be the same rocksdb that collocatordb was built against. dereko2vec
+itself does not include any rocksdb header, but it links what collocatordb
+refers to, and symbols of one version do not exist in another. Where the
+script of step 2 was used for both, this is already taken care of.
 
-Linking rocksdb and collocatordb statically makes counting collocations about
-22% faster, measured with 2 million increments against rocksdb 7.8.3. On an
-indexing run of two weeks that is about three days. Name the two static
-libraries, the compression libraries stay shared:
-
-```bash
-cmake -S . -B build \
-      -DCOLLOCATORDB=/usr/local/lib64/libcollocatordb_static.a \
-      -DROCKSDB=$HOME/rocksdb/lib64/librocksdb.a
-```
-
-`lib64` on Fedora, Rocky Linux and RHEL, `lib` on Debian and Ubuntu. Debian and
-Ubuntu ship `librocksdb.a` in `librocksdb-dev`, elsewhere it comes out of a
-rocksdb built by hand, see the collocatordb README.
-
-This does not need static versions of zlib, snappy, lz4 and zstd, which Rocky
-Linux, RHEL and Fedora do not ship. Only `-DSTATIC_DEREKO2VEC=ON`, which builds
-a completely static binary, needs those, and is rarely worth the trouble.
+A completely static binary, `-DSTATIC_DEREKO2VEC=ON`, needs static versions of
+zlib, snappy, lz4 and zstd on top, which Rocky Linux, RHEL and Fedora do not
+ship, and is rarely worth the trouble.
 
 ### If dereko2vec does not start
 
diff --git a/scripts/build-rocksdb.sh b/scripts/build-rocksdb.sh
new file mode 100755
index 0000000..36e4565
--- /dev/null
+++ b/scripts/build-rocksdb.sh
@@ -0,0 +1,147 @@
+#!/usr/bin/env bash
+#
+# Builds rocksdb once, with the shared and the static library, and installs it
+# into a prefix of its own (default: $HOME/rocksdb). Works on Fedora, Rocky
+# Linux, RHEL, Debian, Ubuntu and MacOS.
+#
+# The version to build is, in this order:
+#   1. the one given with -v
+#   2. the one of the rocksdb package of the distribution, so that the static
+#      library matches the headers and the shared library collocatordb was
+#      built against
+#   3. a pinned one that is known to compile with the compilers of Rocky Linux
+#      9 (gcc 11) up to Fedora (gcc 16) and MacOS (clang)
+#
+# Examples:
+#   scripts/build-rocksdb.sh                  # build the version of the distribution
+#   scripts/build-rocksdb.sh -v 10.2.1        # build a specific version
+#   scripts/build-rocksdb.sh -p /opt/rocksdb  # install somewhere else
+#
+set -euo pipefail
+
+PINNED_VERSION=10.2.1
+PREFIX=$HOME/rocksdb
+VERSION=
+SOURCE_DIR=
+STATIC_ONLY=0
+
+usage() {
+    sed -n '2,17p' "$0"
+    exit "${1:-0}"
+}
+
+while [ $# -gt 0 ]; do
+    case $1 in
+        -p|--prefix)  PREFIX=$2; shift 2 ;;
+        -v|--version) VERSION=$2; shift 2 ;;
+        -s|--source)  SOURCE_DIR=$2; shift 2 ;;
+        --static-only) STATIC_ONLY=1; shift ;;
+        -h|--help)    usage 0 ;;
+        *) echo "Unknown option: $1" >&2; usage 1 ;;
+    esac
+done
+
+SOURCE_DIR=${SOURCE_DIR:-$PREFIX-src}
+
+# --- the version -------------------------------------------------------------
+if [ -z "$VERSION" ]; then
+    if command -v rpm > /dev/null && rpm -q rocksdb > /dev/null 2>&1; then
+        VERSION=$(rpm -q --qf '%{VERSION}' rocksdb)
+    elif command -v dpkg-query > /dev/null && dpkg-query -W librocksdb-dev > /dev/null 2>&1; then
+        VERSION=$(dpkg-query -W -f '${Version}' librocksdb-dev | cut -d- -f1)
+    elif command -v brew > /dev/null && brew list --versions rocksdb > /dev/null 2>&1; then
+        VERSION=$(brew list --versions rocksdb | awk '{print $2}' | cut -d' ' -f1)
+    else
+        VERSION=$PINNED_VERSION
+        echo "No rocksdb package found, building the pinned version $VERSION."
+        echo "Give another one with -v, see https://github.com/facebook/rocksdb/tags"
+    fi
+fi
+echo "Building rocksdb $VERSION"
+
+# --- the prerequisites -------------------------------------------------------
+missing=
+for tool in git cmake make; do
+    command -v $tool > /dev/null || missing="$missing $tool"
+done
+if ! command -v c++ > /dev/null && ! command -v g++ > /dev/null && ! command -v clang++ > /dev/null; then
+    missing="$missing c++"
+fi
+# The compression libraries rocksdb is built with below. Where they are
+# missing the build still succeeds, just without them, so this is a hint.
+compression_hint=
+if command -v pkg-config > /dev/null; then
+    for lib in snappy zlib bzip2 liblz4 libzstd; do
+        pkg-config --exists $lib 2> /dev/null || compression_hint="$compression_hint $lib"
+    done
+fi
+if [ -n "$missing" ]; then
+    echo "Missing build tools:$missing" >&2
+    echo >&2
+    echo "Install them and the compression libraries:" >&2
+    echo "  Fedora, Rocky, RHEL: sudo dnf install cmake gcc-c++ git snappy-devel zlib-devel bzip2-devel lz4-devel libzstd-devel" >&2
+    echo "  Debian, Ubuntu:      sudo apt-get install cmake g++ git libsnappy-dev zlib1g-dev libbz2-dev liblz4-dev libzstd-dev" >&2
+    echo "  MacOS:               brew install cmake snappy zlib bzip2 lz4 zstd" >&2
+    exit 1
+fi
+if [ -n "$compression_hint" ]; then
+    echo "Warning: pkg-config does not find:$compression_hint" >&2
+    echo "rocksdb will be built without them. The devel packages named above provide them." >&2
+fi
+
+# --- the sources -------------------------------------------------------------
+if [ -d "$SOURCE_DIR/.git" ]; then
+    echo "Reusing the checkout in $SOURCE_DIR"
+    git -C "$SOURCE_DIR" fetch --depth 1 origin "refs/tags/v$VERSION"
+    git -C "$SOURCE_DIR" checkout -q FETCH_HEAD
+else
+    git clone https://github.com/facebook/rocksdb.git --branch "v$VERSION" --depth 1 "$SOURCE_DIR"
+fi
+
+# --- the build ---------------------------------------------------------------
+# lib64 where the distribution has one (Fedora, Rocky, RHEL, openSUSE), lib
+# elsewhere. Both are searched for a prefix by cmake, this is for the user.
+if [ -d /usr/lib64 ] && [ ! -e /etc/debian_version ]; then
+    LIBDIR=lib64
+else
+    LIBDIR=lib
+fi
+
+# WITH_GFLAGS and WITH_LIBURING are off so that the static library does not
+# drag them into everything that links it. FAIL_ON_WARNINGS off so that a
+# newer compiler does not turn rocksdb's own warnings into errors. And
+# -include cstdint because older rocksdb versions declare uint64_t and friends
+# without including it, which newer compilers no longer tolerate - Fedora 44
+# packages 10.2.1 and builds it with gcc 16, for instance. Where it is already
+# included, the flag changes nothing.
+cmake -S "$SOURCE_DIR" -B "$SOURCE_DIR/build" \
+      -DCMAKE_BUILD_TYPE=Release \
+      -DCMAKE_CXX_FLAGS="-include cstdint" \
+      -DFAIL_ON_WARNINGS=OFF \
+      -DWITH_TESTS=OFF -DWITH_ALL_TESTS=OFF \
+      -DWITH_BENCHMARK_TOOLS=OFF -DWITH_TOOLS=OFF -DWITH_CORE_TOOLS=OFF \
+      -DWITH_GFLAGS=OFF -DWITH_LIBURING=OFF \
+      -DWITH_SNAPPY=ON -DWITH_LZ4=ON -DWITH_ZLIB=ON -DWITH_ZSTD=ON -DWITH_BZ2=ON \
+      -DROCKSDB_BUILD_SHARED=$([ $STATIC_ONLY = 1 ] && echo OFF || echo ON) \
+      -DCMAKE_INSTALL_PREFIX="$PREFIX" \
+      -DCMAKE_INSTALL_LIBDIR="$LIBDIR"
+cmake --build "$SOURCE_DIR/build" -j "$(getconf _NPROCESSORS_ONLN 2> /dev/null || sysctl -n hw.ncpu)"
+cmake --install "$SOURCE_DIR/build"
+
+# --- what to do with it ------------------------------------------------------
+echo
+echo "Installed rocksdb $VERSION:"
+echo "  headers:  $PREFIX/include"
+echo "  static:   $PREFIX/$LIBDIR/librocksdb.a"
+[ $STATIC_ONLY = 1 ] || echo "  shared:   $PREFIX/$LIBDIR/$( [ "$(uname)" = Darwin ] && echo librocksdb.dylib || echo librocksdb.so )"
+echo
+echo "Build collocatordb against it with:"
+echo "  cmake -S . -B build -DCMAKE_PREFIX_PATH=$PREFIX -DCMAKE_INSTALL_PREFIX=/usr/local"
+echo
+echo "Build dereko2vec against it with:"
+echo "  cmake -S . -B build -DSTATIC_ROCKSDB=ON -DCMAKE_PREFIX_PATH=$PREFIX"
+if [ $STATIC_ONLY = 0 ] && [ "$(uname)" = Linux ]; then
+    echo
+    echo "Programs that use the shared library find it after:"
+    echo "  echo $PREFIX/$LIBDIR | sudo tee /etc/ld.so.conf.d/rocksdb.conf && sudo ldconfig"
+fi