diff --git a/libnetwork/etchosts/etchosts.go b/libnetwork/etchosts/etchosts.go
index 7832ebe673..35845fe94a 100644
--- a/libnetwork/etchosts/etchosts.go
+++ b/libnetwork/etchosts/etchosts.go
@@ -8,7 +8,6 @@ import (
 	"net/netip"
 	"os"
 	"regexp"
-	"strings"
 	"sync"
 )
 
@@ -71,56 +70,27 @@ func Drop(path string) {
 
 // Build function
 // path is path to host file string required
-// IP, hostname, and domainname set main record leave empty for no master record
 // extraContent is an array of extra host records.
-func Build(path, IP, hostname, domainname string, extraContent []Record) error {
-	return build(path, IP, hostname, domainname, defaultContentIPv4, defaultContentIPv6, extraContent)
+func Build(path string, extraContent []Record) error {
+	return build(path, defaultContentIPv4, defaultContentIPv6, extraContent)
 }
 
 // BuildNoIPv6 is the same as Build, but will not include IPv6 entries.
-func BuildNoIPv6(path, IP, hostname, domainname string, extraContent []Record) error {
-	if isIPv6(IP) {
-		IP = ""
-	}
-
+func BuildNoIPv6(path string, extraContent []Record) error {
 	var ipv4ExtraContent []Record
 	for _, rec := range extraContent {
-		if !isIPv6(rec.IP) {
+		addr, err := netip.ParseAddr(rec.IP)
+		if err != nil || !addr.Is6() {
 			ipv4ExtraContent = append(ipv4ExtraContent, rec)
 		}
 	}
-
-	return build(path, IP, hostname, domainname, defaultContentIPv4, ipv4ExtraContent)
+	return build(path, defaultContentIPv4, ipv4ExtraContent)
 }
 
-func isIPv6(s string) bool {
-	addr, err := netip.ParseAddr(s)
-	return err == nil && addr.Is6()
-}
-
-func build(path, IP, hostname, domainname string, contents ...[]Record) error {
+func build(path string, contents ...[]Record) error {
 	defer pathLock(path)()
 
 	buf := bytes.NewBuffer(nil)
-	if IP != "" {
-		// set main record
-		var mainRec Record
-		mainRec.IP = IP
-		// User might have provided a FQDN in hostname or split it across hostname
-		// and domainname.  We want the FQDN and the bare hostname.
-		fqdn := hostname
-		if domainname != "" {
-			fqdn += "." + domainname
-		}
-		mainRec.Hosts = fqdn
-
-		if hostName, _, ok := strings.Cut(fqdn, "."); ok {
-			mainRec.Hosts += " " + hostName
-		}
-		if _, err := mainRec.WriteTo(buf); err != nil {
-			return err
-		}
-	}
 
 	// Write content from function arguments
 	for _, content := range contents {
diff --git a/libnetwork/etchosts/etchosts_test.go b/libnetwork/etchosts/etchosts_test.go
index 96bb10fb3c..9f7f061ec3 100644
--- a/libnetwork/etchosts/etchosts_test.go
+++ b/libnetwork/etchosts/etchosts_test.go
@@ -21,7 +21,7 @@ func TestBuildDefault(t *testing.T) {
 
 	// check that /etc/hosts has consistent ordering
 	for i := 0; i <= 5; i++ {
-		err = Build(file.Name(), "", "", "", nil)
+		err = Build(file.Name(), nil)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -42,7 +42,7 @@ func TestBuildNoIPv6(t *testing.T) {
 	d := t.TempDir()
 	filename := filepath.Join(d, "hosts")
 
-	err := BuildNoIPv6(filename, "fdbb:c59c:d015::2", "an.example", "", []Record{
+	err := BuildNoIPv6(filename, []Record{
 		{
 			Hosts: "another.example",
 			IP:    "fdbb:c59c:d015::3",
@@ -58,94 +58,6 @@ func TestBuildNoIPv6(t *testing.T) {
 	assert.Check(t, is.DeepEqual(string(content), "127.0.0.1\tlocalhost\n10.11.12.13\tanother.example\n"))
 }
 
-func TestBuildHostnameDomainname(t *testing.T) {
-	file, err := os.CreateTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.Remove(file.Name())
-
-	err = Build(file.Name(), "10.11.12.13", "testhostname", "testdomainname", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	content, err := os.ReadFile(file.Name())
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if expected := "10.11.12.13\ttesthostname.testdomainname testhostname\n"; !bytes.Contains(content, []byte(expected)) {
-		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
-	}
-}
-
-func TestBuildHostname(t *testing.T) {
-	file, err := os.CreateTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.Remove(file.Name())
-
-	err = Build(file.Name(), "10.11.12.13", "testhostname", "", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	content, err := os.ReadFile(file.Name())
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if expected := "10.11.12.13\ttesthostname\n"; !bytes.Contains(content, []byte(expected)) {
-		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
-	}
-}
-
-func TestBuildHostnameFQDN(t *testing.T) {
-	file, err := os.CreateTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.Remove(file.Name())
-
-	err = Build(file.Name(), "10.11.12.13", "testhostname.testdomainname.com", "", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	content, err := os.ReadFile(file.Name())
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if expected := "10.11.12.13\ttesthostname.testdomainname.com testhostname\n"; !bytes.Contains(content, []byte(expected)) {
-		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
-	}
-}
-
-func TestBuildNoIP(t *testing.T) {
-	file, err := os.CreateTemp("", "")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.Remove(file.Name())
-
-	err = Build(file.Name(), "", "testhostname", "", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	content, err := os.ReadFile(file.Name())
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if expected := ""; !bytes.Contains(content, []byte(expected)) {
-		t.Fatalf("Expected to find '%s' got '%s'", expected, content)
-	}
-}
-
 func TestUpdate(t *testing.T) {
 	file, err := os.CreateTemp("", "")
 	if err != nil {
@@ -153,7 +65,12 @@ func TestUpdate(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	if err := Build(file.Name(), "10.11.12.13", "testhostname", "testdomainname", nil); err != nil {
+	if err := Build(file.Name(), []Record{
+		{
+			"testhostname.testdomainname testhostname",
+			"10.11.12.13",
+		},
+	}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -194,7 +111,7 @@ func TestUpdateIgnoresPrefixedHostname(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	if err := Build(file.Name(), "10.11.12.13", "testhostname", "testdomainname", []Record{
+	if err := Build(file.Name(), []Record{
 		{
 			Hosts: "prefix",
 			IP:    "2.2.2.2",
@@ -245,7 +162,7 @@ func TestDeleteIgnoresPrefixedHostname(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -293,7 +210,7 @@ func TestAddEmpty(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -310,7 +227,7 @@ func TestAdd(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -341,7 +258,7 @@ func TestDeleteEmpty(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -381,7 +298,7 @@ func TestDelete(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -437,7 +354,7 @@ func TestConcurrentWrites(t *testing.T) {
 	}
 	defer os.Remove(file.Name())
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -502,7 +419,7 @@ func benchDelete(b *testing.B) {
 		b.StartTimer()
 	}()
 
-	err = Build(file.Name(), "", "", "", nil)
+	err = Build(file.Name(), nil)
 	if err != nil {
 		b.Fatal(err)
 	}
diff --git a/libnetwork/sandbox_dns_unix.go b/libnetwork/sandbox_dns_unix.go
index 40f1a7b46f..a03f4ae419 100644
--- a/libnetwork/sandbox_dns_unix.go
+++ b/libnetwork/sandbox_dns_unix.go
@@ -120,7 +120,7 @@ func (sb *Sandbox) buildHostsFile() error {
 	if en, ok := sb.ipv6Enabled(); ok && !en {
 		buildf = etchosts.BuildNoIPv6
 	}
-	if err := buildf(sb.config.hostsPath, "", sb.config.hostName, sb.config.domainName, extraContent); err != nil {
+	if err := buildf(sb.config.hostsPath, extraContent); err != nil {
 		return err
 	}