Index: head/contrib/netbsd-tests/lib/libc/gen/t_setdomainname.c
===================================================================
--- head/contrib/netbsd-tests/lib/libc/gen/t_setdomainname.c
+++ head/contrib/netbsd-tests/lib/libc/gen/t_setdomainname.c
@@ -34,11 +34,13 @@
 #include <sys/param.h>
 
 #include <atf-c.h>
+#include <err.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <string.h>
 #include <unistd.h>
 
-static char domain[MAXHOSTNAMELEN];
+#define	DOMAIN_BACKUP_FILE "domain.bak"
 
 static const char domains[][MAXHOSTNAMELEN] = {
 	"1234567890",
@@ -47,6 +49,45 @@
 	"--------------------------------------------------------------------"
 };
 
+static void
+backup_domain(void)
+{
+	char domain[MAXHOSTNAMELEN];
+	int fd;
+	size_t l;
+	ssize_t r,n = 0;
+
+	memset(domain, 0, sizeof(domain));
+
+	ATF_REQUIRE_EQ(0, getdomainname(domain, sizeof(domain)));
+	l = strnlen(domain, MAXHOSTNAMELEN);
+	fd = open(DOMAIN_BACKUP_FILE, O_WRONLY | O_CREAT | O_EXCL, 0644);
+	ATF_REQUIRE(fd >= 0);
+	while ((r = write(fd, domain + n, l - n)) > 0)
+		n += r;
+	ATF_REQUIRE_EQ(0, r);
+	close(fd);
+}
+
+static void
+restore_domain(void)
+{
+	char domain[MAXHOSTNAMELEN];
+	int fd;
+	ssize_t r, n = 0;
+
+	memset(domain, 0, sizeof(domain));
+	if ((fd = open(DOMAIN_BACKUP_FILE, O_RDONLY)) < 0)
+		err(1, "open");
+	while ((r = read(fd, domain + n, sizeof(domain) - n)) > 0)
+		n += r;
+	if (r < 0)
+		err(1, "read");
+	if (setdomainname(domain, strlen(domain)) != 0)
+		err(1, "setdomainname");
+	close(fd);
+}
+
 ATF_TC_WITH_CLEANUP(setdomainname_basic);
 ATF_TC_HEAD(setdomainname_basic, tc)
 {
@@ -59,6 +100,7 @@
 	char name[MAXHOSTNAMELEN];
 	size_t i;
 
+	backup_domain();
 	for (i = 0; i < __arraycount(domains); i++) {
 
 		(void)memset(name, 0, sizeof(name));
@@ -80,12 +122,11 @@
 		ATF_REQUIRE(strcmp(domains[i], name) == 0);
 	}
 
-	(void)setdomainname(domain, sizeof(domain));
 }
 
 ATF_TC_CLEANUP(setdomainname_basic, tc)
 {
-	(void)setdomainname(domain, sizeof(domain));
+	restore_domain();
 }
 
 ATF_TC_WITH_CLEANUP(setdomainname_limit);
@@ -100,6 +141,7 @@
 	char name[MAXHOSTNAMELEN + 1];
 
 	(void)memset(name, 0, sizeof(name));
+	backup_domain();
 
 #ifdef __FreeBSD__
 	ATF_REQUIRE(setdomainname(name, MAXHOSTNAMELEN - 1 ) == 0);
@@ -110,10 +152,10 @@
 
 ATF_TC_CLEANUP(setdomainname_limit, tc)
 {
-	(void)setdomainname(domain, sizeof(domain));
+	restore_domain();
 }
 
-ATF_TC_WITH_CLEANUP(setdomainname_perm);
+ATF_TC(setdomainname_perm);
 ATF_TC_HEAD(setdomainname_perm, tc)
 {
 	atf_tc_set_md_var(tc, "descr", "Can normal user set the domain name?");
@@ -122,24 +164,16 @@
 
 ATF_TC_BODY(setdomainname_perm, tc)
 {
+	char domain[MAXHOSTNAMELEN];
 
-	errno = 0;
+	memset(domain, 0, sizeof(domain));
 
+	errno = 0;
 	ATF_REQUIRE_ERRNO(EPERM, setdomainname(domain, sizeof(domain)) == -1);
 }
 
-ATF_TC_CLEANUP(setdomainname_perm, tc)
-{
-	(void)setdomainname(domain, sizeof(domain));
-}
-
 ATF_TP_ADD_TCS(tp)
 {
-
-	(void)memset(domain, 0, sizeof(domain));
-
-	ATF_REQUIRE(getdomainname(domain, sizeof(domain)) == 0);
-
 	ATF_TP_ADD_TC(tp, setdomainname_basic);
 	ATF_TP_ADD_TC(tp, setdomainname_limit);
 	ATF_TP_ADD_TC(tp, setdomainname_perm);
Index: head/lib/libc/tests/gen/Makefile
===================================================================
--- head/lib/libc/tests/gen/Makefile
+++ head/lib/libc/tests/gen/Makefile
@@ -72,6 +72,7 @@
 SRCS.fmtcheck2_test=	fmtcheck_test.c
 SRCS.fnmatch2_test=	fnmatch_test.c
 
+TEST_METADATA.setdomainname_test+=	is_exclusive=true
 TESTS_SUBDIRS=	execve
 TESTS_SUBDIRS+=	posix_spawn