diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index f27a83e1f8..9f7aef1a93 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.577 2009/04/05 04:19:58 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/postmaster/postmaster.c,v 1.578 2009/05/02 22:02:37 tgl Exp $
  *
  * NOTES
  *
@@ -315,6 +315,7 @@ extern int	optreset;			/* might not be declared by system headers */
 /*
  * postmaster.c - function prototypes
  */
+static void getInstallationPaths(const char *argv0);
 static void checkDataDir(void);
 
 #ifdef USE_BONJOUR
@@ -493,11 +494,8 @@ PostmasterMain(int argc, char *argv[])
 											  ALLOCSET_DEFAULT_MAXSIZE);
 	MemoryContextSwitchTo(PostmasterContext);
 
-	if (find_my_exec(argv[0], my_exec_path) < 0)
-		elog(FATAL, "%s: could not locate my own executable path",
-			 argv[0]);
-
-	get_pkglib_path(my_exec_path, pkglib_path);
+	/* Initialize paths to installation files */
+	getInstallationPaths(argv[0]);
 
 	/*
 	 * Options setup
@@ -690,15 +688,6 @@ PostmasterMain(int argc, char *argv[])
 		ExitPostmaster(1);
 	}
 
-#ifdef EXEC_BACKEND
-	/* Locate executable backend before we change working directory */
-	if (find_other_exec(argv[0], "postgres", PG_BACKEND_VERSIONSTR,
-						postgres_exec_path) < 0)
-		ereport(FATAL,
-				(errmsg("%s: could not locate matching postgres executable",
-						progname)));
-#endif
-
 	/*
 	 * Locate the proper configuration files and data directory, and read
 	 * postgresql.conf for the first time.
@@ -1062,6 +1051,58 @@ PostmasterMain(int argc, char *argv[])
 }
 
 
+/*
+ * Compute and check the directory paths to files that are part of the
+ * installation (as deduced from the postgres executable's own location)
+ */
+static void
+getInstallationPaths(const char *argv0)
+{
+	DIR		   *pdir;
+
+	/* Locate the postgres executable itself */
+	if (find_my_exec(argv0, my_exec_path) < 0)
+		elog(FATAL, "%s: could not locate my own executable path", argv0);
+
+#ifdef EXEC_BACKEND
+	/* Locate executable backend before we change working directory */
+	if (find_other_exec(argv0, "postgres", PG_BACKEND_VERSIONSTR,
+						postgres_exec_path) < 0)
+		ereport(FATAL,
+				(errmsg("%s: could not locate matching postgres executable",
+						argv0)));
+#endif
+
+	/*
+	 * Locate the pkglib directory --- this has to be set early in case we try
+	 * to load any modules from it in response to postgresql.conf entries.
+	 */
+	get_pkglib_path(my_exec_path, pkglib_path);
+
+	/*
+	 * Verify that there's a readable directory there; otherwise the
+	 * Postgres installation is incomplete or corrupt.  (A typical cause
+	 * of this failure is that the postgres executable has been moved or
+	 * hardlinked to some directory that's not a sibling of the installation
+	 * lib/ directory.)
+	 */
+	pdir = AllocateDir(pkglib_path);
+	if (pdir == NULL)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not open directory \"%s\": %m",
+						pkglib_path),
+				 errhint("This may indicate an incomplete PostgreSQL installation, or that the file \"%s\" has been moved away from its proper location.",
+						 my_exec_path)));
+	FreeDir(pdir);
+
+	/*
+	 * XXX is it worth similarly checking the share/ directory?  If the
+	 * lib/ directory is there, then share/ probably is too.
+	 */
+}
+
+
 /*
  * Validate the proposed data directory
  */
diff --git a/src/backend/utils/misc/tzparser.c b/src/backend/utils/misc/tzparser.c
index f7d6c84514..cc688dcaba 100644
--- a/src/backend/utils/misc/tzparser.c
+++ b/src/backend/utils/misc/tzparser.c
@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/tzparser.c,v 1.7 2009/01/01 17:23:53 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/tzparser.c,v 1.8 2009/05/02 22:02:37 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -326,12 +326,41 @@ ParseTzFile(const char *filename, int depth,
 	tzFile = AllocateFile(file_path, "r");
 	if (!tzFile)
 	{
-		/* at level 0, if file doesn't exist, guc.c's complaint is enough */
+		/*
+		 * Check to see if the problem is not the filename but the directory.
+		 * This is worth troubling over because if the installation share/
+		 * directory is missing or unreadable, this is likely to be the first
+		 * place we notice a problem during postmaster startup.
+		 */
+		int			save_errno = errno;
+		DIR		   *tzdir;
+
+		snprintf(file_path, sizeof(file_path), "%s/timezonesets",
+				 share_path);
+		tzdir = AllocateDir(file_path);
+		if (tzdir == NULL)
+		{
+			ereport(tz_elevel,
+					(errcode_for_file_access(),
+					 errmsg("could not open directory \"%s\": %m",
+							file_path),
+					 errhint("This may indicate an incomplete PostgreSQL installation, or that the file \"%s\" has been moved away from its proper location.",
+							 my_exec_path)));
+			return -1;
+		}
+		FreeDir(tzdir);
+		errno = save_errno;
+
+		/*
+		 * otherwise, if file doesn't exist and it's level 0, guc.c's
+		 * complaint is enough
+		 */
 		if (errno != ENOENT || depth > 0)
 			ereport(tz_elevel,
 					(errcode_for_file_access(),
 					 errmsg("could not read time zone file \"%s\": %m",
 							filename)));
+
 		return -1;
 	}