diff --git a/nix/libstore/build.cc b/nix/libstore/build.cc
index 9010ca4e200..935f7aacf83 100644
--- a/nix/libstore/build.cc
+++ b/nix/libstore/build.cc
@@ -3367,9 +3367,6 @@ void DerivationGoal::registerOutputs()
 }
 
 
-string drvsLogDir = "drvs";
-
-
 Path DerivationGoal::openLogFile()
 {
     logSize = 0;
diff --git a/nix/libstore/derivations.cc b/nix/libstore/derivations.cc
index f05296702b3..b6203b1e385 100644
--- a/nix/libstore/derivations.cc
+++ b/nix/libstore/derivations.cc
@@ -211,9 +211,6 @@ bool isFixedOutputDrv(const Derivation & drv)
 }
 
 
-DrvHashes drvHashes;
-
-
 /* Returns the hash of a derivation modulo fixed-output
    subderivations.  A fixed-output derivation is a derivation with one
    output (`out') for which an expected hash and hash algorithm are
diff --git a/nix/libstore/derivations.hh b/nix/libstore/derivations.hh
index 8d5e4d05d46..0fbab3a7a4a 100644
--- a/nix/libstore/derivations.hh
+++ b/nix/libstore/derivations.hh
@@ -77,7 +77,7 @@ Hash hashDerivationModulo(StoreAPI & store, Derivation drv);
 /* Memoisation of hashDerivationModulo(). */
 typedef std::map<Path, Hash> DrvHashes;
 
-extern DrvHashes drvHashes;
+inline DrvHashes drvHashes;
 
 /* Split a string specifying a derivation and a set of outputs
    (/nix/store/hash-foo!out1,out2,...) into the derivation path and
diff --git a/nix/libstore/globals.cc b/nix/libstore/globals.cc
index 8551fea56c0..885ba4eafc1 100644
--- a/nix/libstore/globals.cc
+++ b/nix/libstore/globals.cc
@@ -17,9 +17,6 @@ namespace nix {
 #define DEFAULT_SOCKET_PATH "/daemon-socket/socket"
 
 
-Settings settings;
-
-
 Settings::Settings()
 {
     keepFailed = false;
@@ -205,7 +202,4 @@ Settings::SettingsMap Settings::getOverrides()
 }
 
 
-const string nixVersion = PACKAGE_VERSION;
-
-
 }
diff --git a/nix/libstore/globals.hh b/nix/libstore/globals.hh
index 7cfa06e76c1..c2824789ede 100644
--- a/nix/libstore/globals.hh
+++ b/nix/libstore/globals.hh
@@ -227,10 +227,10 @@ private:
 
 
 // FIXME: don't use a global variable.
-extern Settings settings;
+inline Settings settings;
 
 
-extern const string nixVersion;
+inline const string nixVersion {PACKAGE_VERSION};
 
 
 }
diff --git a/nix/libstore/local-store.hh b/nix/libstore/local-store.hh
index 20d3c3c8930..4d529b37a44 100644
--- a/nix/libstore/local-store.hh
+++ b/nix/libstore/local-store.hh
@@ -19,7 +19,7 @@ namespace nix {
 const int nixSchemaVersion = 7;
 
 
-extern string drvsLogDir;
+inline std::string drvsLogDir {"drvs"};
 
 
 struct Derivation;
@@ -293,6 +293,8 @@ void canonicaliseTimestampAndPermissions(const Path & path);
 MakeError(PathInUse, Error);
 
 /* Size below which a file is not considered for deduplication.  */
-extern const size_t deduplicationMinSize;
+/* Any file smaller than this is not considered for deduplication.
+   Keep in sync with (guix store deduplication).  */
+inline const size_t deduplicationMinSize {8192};
 
 }
diff --git a/nix/libstore/optimise-store.cc b/nix/libstore/optimise-store.cc
index d69c43e9978..54aa166c344 100644
--- a/nix/libstore/optimise-store.cc
+++ b/nix/libstore/optimise-store.cc
@@ -16,9 +16,6 @@
 
 namespace nix {
 
-/* Any file smaller than this is not considered for deduplication.
-   Keep in sync with (guix store deduplication).  */
-const size_t deduplicationMinSize = 8192;
 
 static void makeWritable(const Path & path)
 {
diff --git a/nix/libstore/store-api.cc b/nix/libstore/store-api.cc
index 1067e44a8e2..26d44f78b19 100644
--- a/nix/libstore/store-api.cc
+++ b/nix/libstore/store-api.cc
@@ -253,16 +253,3 @@ template<class T> T readStorePaths(Source & from)
 template PathSet readStorePaths(Source & from);
 
 }
-
-
-#include "local-store.hh"
-#include "serialise.hh"
-
-
-namespace nix {
-
-
-std::shared_ptr<StoreAPI> store;
-
-
-}
diff --git a/nix/libstore/store-api.hh b/nix/libstore/store-api.hh
index 32a8f2c795f..affa98b179d 100644
--- a/nix/libstore/store-api.hh
+++ b/nix/libstore/store-api.hh
@@ -363,7 +363,7 @@ Paths topoSortPaths(StoreAPI & store, const PathSet & paths);
 
 /* For now, there is a single global store API object, but we'll
    purify that in the future. */
-extern std::shared_ptr<StoreAPI> store;
+inline std::shared_ptr<StoreAPI> store;
 
 
 /* Display a set of paths in human-readable form (i.e., between quotes
diff --git a/nix/libutil/archive.cc b/nix/libutil/archive.cc
index fa9f4398e3c..938fe8d4492 100644
--- a/nix/libutil/archive.cc
+++ b/nix/libutil/archive.cc
@@ -24,8 +24,6 @@ static string archiveVersion1 = "nix-archive-1";
 
 static string caseHackSuffix = "~nix~case~hack~";
 
-PathFilter defaultPathFilter;
-
 
 static void dumpContents(const Path & path, size_t size,
     Sink & sink)
diff --git a/nix/libutil/archive.hh b/nix/libutil/archive.hh
index 9b83a5f288f..03716ab469f 100644
--- a/nix/libutil/archive.hh
+++ b/nix/libutil/archive.hh
@@ -50,7 +50,7 @@ struct PathFilter
     virtual bool operator () (const Path & path) { return true; }
 };
 
-extern PathFilter defaultPathFilter;
+inline PathFilter defaultPathFilter;
 
 void dumpPath(const Path & path, Sink & sink,
     PathFilter & filter = defaultPathFilter);
diff --git a/nix/libutil/hash.cc b/nix/libutil/hash.cc
index 57b369d4a9b..ac9eb14514b 100644
--- a/nix/libutil/hash.cc
+++ b/nix/libutil/hash.cc
@@ -103,10 +103,6 @@ unsigned int hashLength32(const Hash & hash)
 }
 
 
-// omitted: E O U T
-const string base32Chars = "0123456789abcdfghijklmnpqrsvwxyz";
-
-
 string printHash32(const Hash & hash)
 {
     Hash hash2(hash);
diff --git a/nix/libutil/hash.hh b/nix/libutil/hash.hh
index 1a6b35f074b..cedb5077c16 100644
--- a/nix/libutil/hash.hh
+++ b/nix/libutil/hash.hh
@@ -2,14 +2,15 @@
 
 #include <gcrypt.h>
 
+#include "archive.hh"
 #include "types.hh"
 #include "serialise.hh"
 
 
 namespace nix {
 
-
-extern const string base32Chars;
+// omitted: E O U T
+inline const string base32Chars {"0123456789abcdfghijklmnpqrsvwxyz"};
 
 typedef enum {
     htUnknown = 0,
@@ -79,8 +80,6 @@ Hash hashFile(HashType ht, const Path & path);
 
 /* Compute the hash of the given path.  The hash is defined as
    (essentially) hashString(ht, dumpPath(path)). */
-struct PathFilter;
-extern PathFilter defaultPathFilter;
 typedef std::pair<Hash, unsigned long long> HashResult;
 HashResult hashPath(HashType ht, const Path & path,
     PathFilter & filter = defaultPathFilter);
diff --git a/nix/libutil/util.cc b/nix/libutil/util.cc
index 22022db51a5..ed1a371dfe1 100644
--- a/nix/libutil/util.cc
+++ b/nix/libutil/util.cc
@@ -600,9 +600,6 @@ void createSymlink(const Path & target, const Path & link)
 }
 
 
-LogType logType = ltPretty;
-Verbosity verbosity = lvlInfo;
-
 static int nestingLevel = 0;
 
 
@@ -691,9 +688,6 @@ void writeToStderr(const string & s)
 }
 
 
-void (*_writeToStderr) (const unsigned char * buf, size_t count) = 0;
-
-
 void readFull(int fd, unsigned char * buf, size_t count)
 {
     while (count) {
@@ -1250,7 +1244,6 @@ void keepOnExec(int fd)
 //////////////////////////////////////////////////////////////////////
 
 
-volatile sig_atomic_t _isInterrupted = 0;
 
 void _interrupted()
 {
diff --git a/nix/libutil/util.hh b/nix/libutil/util.hh
index 436c378cb6e..42cb60ea0d4 100644
--- a/nix/libutil/util.hh
+++ b/nix/libutil/util.hh
@@ -132,8 +132,8 @@ typedef enum {
     ltFlat      /* no nesting */
 } LogType;
 
-extern LogType logType;
-extern Verbosity verbosity; /* suppress msgs > this */
+inline LogType logType {ltPretty};
+inline Verbosity verbosity {lvlInfo}; /* suppress msgs > this */
 
 class Nest
 {
@@ -167,7 +167,7 @@ void warnOnce(bool & haveWarned, std::string_view fs);
 
 void writeToStderr(const string & s);
 
-extern void (*_writeToStderr) (const unsigned char * buf, size_t count);
+inline void (*_writeToStderr) (const unsigned char * buf, size_t count) = 0;
 
 
 /* Wrappers arount read()/write() that read/write exactly the
@@ -323,7 +323,7 @@ void commonChildInit(Pipe & logPipe);
 
 /* User interruption. */
 
-extern volatile sig_atomic_t _isInterrupted;
+inline volatile sig_atomic_t _isInterrupted = 0;
 
 void _interrupted();
 
diff --git a/nix/local.mk b/nix/local.mk
index 819131b5d44..2c93670843c 100644
--- a/nix/local.mk
+++ b/nix/local.mk
@@ -113,7 +113,7 @@ guix_daemon_LDADD =				\
   $(SQLITE3_LIBS) $(LIBGCRYPT_LIBS)
 
 guix_daemon_headers =				\
-  %D%/nix-daemon/shared.hh
+  %D%/nix-daemon/nix-daemon.hh
 
 if HAVE_LIBBZ2
 
diff --git a/nix/nix-daemon/guix-daemon.cc b/nix/nix-daemon/guix-daemon.cc
index af09839932f..341e39c2907 100644
--- a/nix/nix-daemon/guix-daemon.cc
+++ b/nix/nix-daemon/guix-daemon.cc
@@ -17,12 +17,12 @@
    You should have received a copy of the GNU General Public License
    along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.  */
 
-#include <config.h>
+#include "config.h"
 
-#include <types.hh>
-#include "shared.hh"
-#include <globals.hh>
-#include <util.hh>
+#include "types.hh"
+#include "nix-daemon.hh"
+#include "globals.hh"
+#include "util.hh"
 
 #include <gcrypt.h>
 
@@ -36,20 +36,13 @@
 #include <netdb.h>
 #include <strings.h>
 #include <exception>
-#include <iostream>
 #include <format>
 
 #include <libintl.h>
 #include <locale.h>
 
-/* Variables used by `nix-daemon.cc'.  */
-volatile ::sig_atomic_t blockInt;
-char **argvSaved;
-
 using namespace nix;
 
-/* Entry point in `nix-daemon.cc'.  */
-extern void run (const std::vector<int> &);
 
 
 /* Command-line options.  */
diff --git a/nix/nix-daemon/nix-daemon.cc b/nix/nix-daemon/nix-daemon.cc
index 3890adb2c74..b3cdb699ac2 100644
--- a/nix/nix-daemon/nix-daemon.cc
+++ b/nix/nix-daemon/nix-daemon.cc
@@ -1,5 +1,5 @@
 #include "config.h"
-#include "shared.hh"
+#include "nix-daemon.hh"
 #include "local-store.hh"
 #include "util.hh"
 #include "serialise.hh"
diff --git a/nix/nix-daemon/shared.hh b/nix/nix-daemon/nix-daemon.hh
similarity index 81%
rename from nix/nix-daemon/shared.hh
rename to nix/nix-daemon/nix-daemon.hh
index 98ec97410b7..8791c4f21fd 100644
--- a/nix/nix-daemon/shared.hh
+++ b/nix/nix-daemon/nix-daemon.hh
@@ -20,9 +20,14 @@
 
 #pragma once
 
+#include <vector>
+
 #include <stdlib.h>
 #include <signal.h>
 
-extern volatile ::sig_atomic_t blockInt;
+/* Variables used by `nix-daemon.cc'.  */
+inline volatile ::sig_atomic_t blockInt;
+inline char **argvSaved;
 
-extern char **argvSaved;
+/* Entry point in `nix-daemon.cc'.  */
+void run (const std::vector<int> &);