Disable swap for kubelet (#67)

Author: wenxuan0923

aks-flex-node-sudoers

@@ -99,6 +99,7 @@ aks-flex-node ALL=(root) NOPASSWD:SETENV: /usr/bin/test *, /bin/test *
 aks-flex-node ALL=(root) NOPASSWD:SETENV: /sbin/sysctl --system
 aks-flex-node ALL=(root) NOPASSWD:SETENV: /sbin/modprobe overlay
 aks-flex-node ALL=(root) NOPASSWD:SETENV: /sbin/modprobe br_netfilter
+aks-flex-node ALL=(root) NOPASSWD:SETENV: /sbin/swapoff -a
 
 # Configuration file management and reading
 aks-flex-node ALL=(root) NOPASSWD:SETENV: /bin/tee /etc/sysctl.d/k8s.conf

pkg/components/system_configuration/system_configuration_installer.go

@@ -54,15 +54,19 @@ func (i *Installer) Validate(ctx context.Context) error {
 
 // configureSysctl creates and applies sysctl configuration for Kubernetes
 func (i *Installer) configureSysctl() error {
+	// Disable swap immediately - kubelet sees no active swap devices
+	// so it can start successfully. This is a critical step for kubelet compatibility.
+	if err := i.disableSwap(); err != nil {
+		return fmt.Errorf("failed to disable swap: %w", err)
+	}
+
 	sysctlConfig := `# Kubernetes sysctl settings
 net.bridge.bridge-nf-call-iptables = 1
 net.bridge.bridge-nf-call-ip6tables = 1
 net.ipv4.ip_forward = 1
 vm.overcommit_memory = 1
 kernel.panic = 10
-kernel.panic_on_oops = 1
-# Disable swap permanently - required for kubelet
-vm.swappiness = 0`
+kernel.panic_on_oops = 1`
 
 	// Create sysctl directory if it doesn't exist
 	if err := utils.RunSystemCommand("mkdir", "-p", sysctlDir); err != nil {
@@ -111,6 +115,20 @@ func (i *Installer) configureResolvConf() error {
 	return nil
 }
 
+// disableSwap disables swap immediately for kubelet compatibility
+func (i *Installer) disableSwap() error {
+	i.logger.Info("Disabling swap for kubelet compatibility")
+
+	// Disable all swap devices immediately
+	if err := utils.RunSystemCommand("swapoff", "-a"); err != nil {
+		i.logger.WithError(err).Warning("Failed to disable swap - may not be enabled")
+	} else {
+		i.logger.Info("Swap disabled successfully")
+	}
+
+	return nil
+}
+
 // GetName returns the step name
 func (i *Installer) GetName() string {
 	return "SystemConfigured"

pkg/utils/utils.go

@@ -20,7 +20,7 @@ import (
 
 // sudoCommandLists holds the command lists for sudo determination
 var (
-	alwaysNeedsSudo = []string{"apt", "apt-get", "dpkg", "systemctl", "mount", "umount", "modprobe", "sysctl", "azcmagent", "usermod", "kubectl"}
+	alwaysNeedsSudo = []string{"apt", "apt-get", "dpkg", "systemctl", "mount", "umount", "modprobe", "sysctl", "azcmagent", "usermod", "kubectl", "swapoff"}
 	conditionalSudo = []string{"mkdir", "cp", "chmod", "chown", "mv", "tar", "rm", "bash", "install", "ln", "cat"}
 	systemPaths     = []string{"/etc/", "/usr/", "/var/", "/opt/", "/boot/", "/sys/"}
 )