Move auto-generated resolv.conf out of /tmp to prevent accidental cleanup

pkg/agent/config/config.go

@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"github.com/k3s-io/k3s/pkg/agent/proxy"
+	agentutil "github.com/k3s-io/k3s/pkg/agent/util"
 	"github.com/k3s-io/k3s/pkg/cli/cmds"
 	"github.com/k3s-io/k3s/pkg/clientaccess"
 	"github.com/k3s-io/k3s/pkg/containerd"
@@ -306,12 +307,13 @@ func locateOrGenerateResolvConf(envInfo *cmds.Agent) string {
 		}
 	}
 
-	tmpConf := filepath.Join(os.TempDir(), version.Program+"-resolv.conf")
-	if err := ioutil.WriteFile(tmpConf, []byte("nameserver 8.8.8.8\n"), 0444); err != nil {
-		logrus.Errorf("Failed to write %s: %v", tmpConf, err)
+	resolvConf := filepath.Join(envInfo.DataDir, "agent", "etc", "resolv.conf")
+	if err := agentutil.WriteFile(resolvConf, "nameserver 8.8.8.8\n"); err != nil {
+		logrus.Errorf("Failed to write %s: %v", resolvConf, err)
 		return ""
 	}
-	return tmpConf
+	logrus.Warnf("Host resolv.conf includes loopback or multicast nameservers - kubelet will use autogenerated resolv.conf with nameserver 8.8.8.8")
+	return resolvConf
 }
 
 func get(ctx context.Context, envInfo *cmds.Agent, proxy proxy.Proxy) (*config.Node, error) {