diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index e2c01e5625..80dc3b585f 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -33,11 +33,6 @@
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "pg_getopt.h"
-#include "pgstat.h"
-#include "postmaster/bgwriter.h"
-#include "postmaster/startup.h"
-#include "postmaster/walwriter.h"
-#include "replication/walreceiver.h"
 #include "storage/bufmgr.h"
 #include "storage/bufpage.h"
 #include "storage/condition_variable.h"
@@ -47,7 +42,6 @@
 #include "utils/builtins.h"
 #include "utils/fmgroids.h"
 #include "utils/memutils.h"
-#include "utils/ps_status.h"
 #include "utils/rel.h"
 #include "utils/relmapper.h"
 
@@ -56,7 +50,6 @@ uint32		bootstrap_data_checksum_version = 0;	/* No checksum */
 
 static void CheckerModeMain(void);
 static void bootstrap_signals(void);
-static void ShutdownAuxiliaryProcess(int code, Datum arg);
 static Form_pg_attribute AllocateAttribute(void);
 static void populate_typ_list(void);
 static Oid	gettype(char *type);
@@ -67,8 +60,6 @@ static void cleanup(void);
  * ----------------
  */
 
-AuxProcType MyAuxProcType = NotAnAuxProcess;	/* declared in miscadmin.h */
-
 Relation	boot_reldesc;		/* current relation descriptor */
 
 Form_pg_attribute attrtypes[MAXATTR];	/* points to attribute info */
@@ -184,139 +175,6 @@ typedef struct _IndexList
 static IndexList *ILHead = NULL;
 
 
-/*
- *	 AuxiliaryProcessMain
- *
- *	 The main entry point for auxiliary processes, such as the bgwriter,
- *	 walwriter, walreceiver, bootstrapper and the shared memory checker code.
- *
- *	 This code is here just because of historical reasons.
- */
-void
-AuxiliaryProcessMain(AuxProcType auxtype)
-{
-	Assert(IsUnderPostmaster);
-
-	MyAuxProcType = auxtype;
-
-	switch (MyAuxProcType)
-	{
-		case StartupProcess:
-			MyBackendType = B_STARTUP;
-			break;
-		case ArchiverProcess:
-			MyBackendType = B_ARCHIVER;
-			break;
-		case BgWriterProcess:
-			MyBackendType = B_BG_WRITER;
-			break;
-		case CheckpointerProcess:
-			MyBackendType = B_CHECKPOINTER;
-			break;
-		case WalWriterProcess:
-			MyBackendType = B_WAL_WRITER;
-			break;
-		case WalReceiverProcess:
-			MyBackendType = B_WAL_RECEIVER;
-			break;
-		default:
-			elog(ERROR, "something has gone wrong");
-			MyBackendType = B_INVALID;
-	}
-
-	init_ps_display(NULL);
-
-	SetProcessingMode(BootstrapProcessing);
-	IgnoreSystemIndexes = true;
-
-	BaseInit();
-
-	/*
-	 * As an auxiliary process, we aren't going to do the full InitPostgres
-	 * pushups, but there are a couple of things that need to get lit up even
-	 * in an auxiliary process.
-	 */
-
-	/*
-	 * Create a PGPROC so we can use LWLocks.  In the EXEC_BACKEND case, this
-	 * was already done by SubPostmasterMain().
-	 */
-#ifndef EXEC_BACKEND
-	InitAuxiliaryProcess();
-#endif
-
-	/*
-	 * Assign the ProcSignalSlot for an auxiliary process.  Since it doesn't
-	 * have a BackendId, the slot is statically allocated based on the
-	 * auxiliary process type (MyAuxProcType).  Backends use slots indexed in
-	 * the range from 1 to MaxBackends (inclusive), so we use MaxBackends +
-	 * AuxProcType + 1 as the index of the slot for an auxiliary process.
-	 *
-	 * This will need rethinking if we ever want more than one of a particular
-	 * auxiliary process type.
-	 */
-	ProcSignalInit(MaxBackends + MyAuxProcType + 1);
-
-	/* finish setting up bufmgr.c */
-	InitBufferPoolBackend();
-
-	/*
-	 * Auxiliary processes don't run transactions, but they may need a
-	 * resource owner anyway to manage buffer pins acquired outside
-	 * transactions (and, perhaps, other things in future).
-	 */
-	CreateAuxProcessResourceOwner();
-
-	/* Initialize statistics reporting */
-	pgstat_initialize();
-
-	/* Initialize backend status information */
-	pgstat_beinit();
-	pgstat_bestart();
-
-	/* register a before-shutdown callback for LWLock cleanup */
-	before_shmem_exit(ShutdownAuxiliaryProcess, 0);
-
-	SetProcessingMode(NormalProcessing);
-
-	switch (MyAuxProcType)
-	{
-		case CheckerProcess:
-		case BootstrapProcess:
-			pg_unreachable();
-			break;
-
-		case StartupProcess:
-			StartupProcessMain();
-			proc_exit(1);
-
-		case ArchiverProcess:
-			PgArchiverMain();
-			proc_exit(1);
-
-		case BgWriterProcess:
-			BackgroundWriterMain();
-			proc_exit(1);
-
-		case CheckpointerProcess:
-			CheckpointerMain();
-			proc_exit(1);
-
-		case WalWriterProcess:
-			InitXLOGAccess();
-			WalWriterMain();
-			proc_exit(1);
-
-		case WalReceiverProcess:
-			WalReceiverMain();
-			proc_exit(1);
-
-		default:
-			elog(PANIC, "unrecognized process type: %d", (int) MyAuxProcType);
-			proc_exit(1);
-	}
-}
-
 /*
  * In shared memory checker mode, all we really want to do is create shared
  * memory and semaphores (just to prove we can do it with the current GUC
@@ -554,21 +412,6 @@ bootstrap_signals(void)
 	pqsignal(SIGQUIT, SIG_DFL);
 }
 
-/*
- * Begin shutdown of an auxiliary process.  This is approximately the equivalent
- * of ShutdownPostgres() in postinit.c.  We can't run transactions in an
- * auxiliary process, so most of the work of AbortTransaction() is not needed,
- * but we do need to make sure we've released any LWLocks we are holding.
- * (This is only critical during an error exit.)
- */
-static void
-ShutdownAuxiliaryProcess(int code, Datum arg)
-{
-	LWLockReleaseAll();
-	ConditionVariableCancelSleep();
-	pgstat_report_wait_end();
-}
-
 /* ----------------------------------------------------------------
  *				MANUAL BACKEND INTERACTIVE INTERFACE COMMANDS
  * ----------------------------------------------------------------
diff --git a/src/backend/postmaster/Makefile b/src/backend/postmaster/Makefile
index bfdf6a833d..787c6a2c3b 100644
--- a/src/backend/postmaster/Makefile
+++ b/src/backend/postmaster/Makefile
@@ -14,6 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = \
 	autovacuum.o \
+	auxprocess.o \
 	bgworker.o \
 	bgwriter.o \
 	checkpointer.o \
diff --git a/src/backend/postmaster/auxprocess.c b/src/backend/postmaster/auxprocess.c
new file mode 100644
index 0000000000..c391c963db
--- /dev/null
+++ b/src/backend/postmaster/auxprocess.c
@@ -0,0 +1,194 @@
+/*-------------------------------------------------------------------------
+ * auxprocess.c
+ *	  functions related to auxiliary processes.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/auxprocess.c
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <unistd.h>
+#include <signal.h>
+
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/auxprocess.h"
+#include "postmaster/bgwriter.h"
+#include "postmaster/startup.h"
+#include "postmaster/walwriter.h"
+#include "replication/walreceiver.h"
+#include "storage/bufmgr.h"
+#include "storage/bufpage.h"
+#include "storage/condition_variable.h"
+#include "storage/ipc.h"
+#include "storage/proc.h"
+#include "tcop/tcopprot.h"
+#include "utils/memutils.h"
+#include "utils/ps_status.h"
+#include "utils/rel.h"
+
+
+static void ShutdownAuxiliaryProcess(int code, Datum arg);
+
+
+/* ----------------
+ *		global variables
+ * ----------------
+ */
+
+AuxProcType MyAuxProcType = NotAnAuxProcess;	/* declared in miscadmin.h */
+
+
+/*
+ *	 AuxiliaryProcessMain
+ *
+ *	 The main entry point for auxiliary processes, such as the bgwriter,
+ *	 walwriter, walreceiver, bootstrapper and the shared memory checker code.
+ *
+ *	 This code is here just because of historical reasons.
+ */
+void
+AuxiliaryProcessMain(AuxProcType auxtype)
+{
+	Assert(IsUnderPostmaster);
+
+	MyAuxProcType = auxtype;
+
+	switch (MyAuxProcType)
+	{
+		case StartupProcess:
+			MyBackendType = B_STARTUP;
+			break;
+		case ArchiverProcess:
+			MyBackendType = B_ARCHIVER;
+			break;
+		case BgWriterProcess:
+			MyBackendType = B_BG_WRITER;
+			break;
+		case CheckpointerProcess:
+			MyBackendType = B_CHECKPOINTER;
+			break;
+		case WalWriterProcess:
+			MyBackendType = B_WAL_WRITER;
+			break;
+		case WalReceiverProcess:
+			MyBackendType = B_WAL_RECEIVER;
+			break;
+		default:
+			elog(ERROR, "something has gone wrong");
+			MyBackendType = B_INVALID;
+	}
+
+	init_ps_display(NULL);
+
+	SetProcessingMode(BootstrapProcessing);
+	IgnoreSystemIndexes = true;
+
+	BaseInit();
+
+	/*
+	 * As an auxiliary process, we aren't going to do the full InitPostgres
+	 * pushups, but there are a couple of things that need to get lit up even
+	 * in an auxiliary process.
+	 */
+
+	/*
+	 * Create a PGPROC so we can use LWLocks.  In the EXEC_BACKEND case, this
+	 * was already done by SubPostmasterMain().
+	 */
+#ifndef EXEC_BACKEND
+	InitAuxiliaryProcess();
+#endif
+
+	/*
+	 * Assign the ProcSignalSlot for an auxiliary process.  Since it doesn't
+	 * have a BackendId, the slot is statically allocated based on the
+	 * auxiliary process type (MyAuxProcType).  Backends use slots indexed in
+	 * the range from 1 to MaxBackends (inclusive), so we use MaxBackends +
+	 * AuxProcType + 1 as the index of the slot for an auxiliary process.
+	 *
+	 * This will need rethinking if we ever want more than one of a particular
+	 * auxiliary process type.
+	 */
+	ProcSignalInit(MaxBackends + MyAuxProcType + 1);
+
+	/* finish setting up bufmgr.c */
+	InitBufferPoolBackend();
+
+	/*
+	 * Auxiliary processes don't run transactions, but they may need a
+	 * resource owner anyway to manage buffer pins acquired outside
+	 * transactions (and, perhaps, other things in future).
+	 */
+	CreateAuxProcessResourceOwner();
+
+	/* Initialize statistics reporting */
+	pgstat_initialize();
+
+	/* Initialize backend status information */
+	pgstat_beinit();
+	pgstat_bestart();
+
+	/* register a before-shutdown callback for LWLock cleanup */
+	before_shmem_exit(ShutdownAuxiliaryProcess, 0);
+
+	SetProcessingMode(NormalProcessing);
+
+	switch (MyAuxProcType)
+	{
+		case CheckerProcess:
+		case BootstrapProcess:
+			pg_unreachable();
+			break;
+
+		case StartupProcess:
+			StartupProcessMain();
+			proc_exit(1);
+
+		case ArchiverProcess:
+			PgArchiverMain();
+			proc_exit(1);
+
+		case BgWriterProcess:
+			BackgroundWriterMain();
+			proc_exit(1);
+
+		case CheckpointerProcess:
+			CheckpointerMain();
+			proc_exit(1);
+
+		case WalWriterProcess:
+			InitXLOGAccess();
+			WalWriterMain();
+			proc_exit(1);
+
+		case WalReceiverProcess:
+			WalReceiverMain();
+			proc_exit(1);
+
+		default:
+			elog(PANIC, "unrecognized process type: %d", (int) MyAuxProcType);
+			proc_exit(1);
+	}
+}
+
+/*
+ * Begin shutdown of an auxiliary process.  This is approximately the equivalent
+ * of ShutdownPostgres() in postinit.c.  We can't run transactions in an
+ * auxiliary process, so most of the work of AbortTransaction() is not needed,
+ * but we do need to make sure we've released any LWLocks we are holding.
+ * (This is only critical during an error exit.)
+ */
+static void
+ShutdownAuxiliaryProcess(int code, Datum arg)
+{
+	LWLockReleaseAll();
+	ConditionVariableCancelSleep();
+	pgstat_report_wait_end();
+}
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index fb948b7257..3864691215 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -95,7 +95,6 @@
 
 #include "access/transam.h"
 #include "access/xlog.h"
-#include "bootstrap/bootstrap.h"
 #include "catalog/pg_control.h"
 #include "common/file_perm.h"
 #include "common/ip.h"
@@ -109,6 +108,7 @@
 #include "pgstat.h"
 #include "port/pg_bswap.h"
 #include "postmaster/autovacuum.h"
+#include "postmaster/auxprocess.h"
 #include "postmaster/bgworker_internals.h"
 #include "postmaster/fork_process.h"
 #include "postmaster/interrupt.h"
diff --git a/src/include/bootstrap/bootstrap.h b/src/include/bootstrap/bootstrap.h
index 0f8762afaf..a982912410 100644
--- a/src/include/bootstrap/bootstrap.h
+++ b/src/include/bootstrap/bootstrap.h
@@ -15,7 +15,6 @@
 #define BOOTSTRAP_H
 
 #include "nodes/execnodes.h"
-#include "miscadmin.h"
 
 
 /*
@@ -34,7 +33,6 @@ extern int	numattr;
 
 
 extern void BootstrapModeMain(int argc, char *argv[]) pg_attribute_noreturn();
-extern void AuxiliaryProcessMain(AuxProcType auxtype) pg_attribute_noreturn();
 
 extern void closerel(char *name);
 extern void boot_openrel(char *name);
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 68d840d699..1b7422d636 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -421,7 +421,7 @@ extern ProcessingMode Mode;
 /*
  * Auxiliary-process type identifiers.  These used to be in bootstrap.h
  * but it seems saner to have them here, with the ProcessingMode stuff.
- * The MyAuxProcType global is defined and set in bootstrap.c.
+ * The MyAuxProcType global is defined and set in auxprocess.c.
  */
 
 typedef enum
diff --git a/src/include/postmaster/auxprocess.h b/src/include/postmaster/auxprocess.h
new file mode 100644
index 0000000000..bc3f541d29
--- /dev/null
+++ b/src/include/postmaster/auxprocess.h
@@ -0,0 +1,20 @@
+/*-------------------------------------------------------------------------
+ * auxprocess.h
+ *	  include file for functions related to auxiliary processes.
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *		src/include/postmaster/auxprocess.h
+ *-------------------------------------------------------------------------
+ */
+#ifndef AUXPROCESS_H
+#define AUXPROCESS_H
+
+#include "miscadmin.h"
+
+extern void AuxiliaryProcessMain(AuxProcType auxtype) pg_attribute_noreturn();
+
+#endif							/* AUXPROCESS_H */