Remove support for automatic kubelet restart

Previously, if the system started without a kubernetes configuration
file, kiOS would start kubelet then watch for the configuration file to
appear. Once it did, it would auto restart the kubelet.

While this was a nice "magic" feature, it had a couple of drawbacks:

- It required bootstrap containers to be aware that they need to write
  the config file last - this is not always clear
- It was relatively black and white - auto restarting only works when
  the system has no configuration at all. Partial configuration could
  not use this method.
- Restarting the container runtime could not be done using this method
- The implementation was poor

For the moment, therefore, this functionality is removed - instead
bootstrap containers should explicitly restart the kubelet by requesting
it via the system socket.

pkgs/bin/init/src/exe.c

@@ -4,6 +4,7 @@
 #include "include/kmsg.h"
 
 #include <stdio.h>
+#include <string.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
 #include <unistd.h>
@@ -13,6 +14,23 @@ int should_restart_processes = 1;
 pid_t crio_pid;
 pid_t kubelet_pid;
 
+/**
+ * Set Hostname From File
+ *
+ * Checks to see if /etc/hostname exists and contains content - if it
+ * does the hostname is updated.
+ */
+static void set_hostname_from_file(void) {
+  char hostname[HOST_NAME_MAX];
+  FILE *fp = fopen("/etc/hostname", "r");
+  if (fp) {
+    if (fgets(hostname, HOST_NAME_MAX, fp)) {
+      sethostname(hostname, strlen(hostname));
+    }
+    fclose(fp);
+  }
+}
+
 /**
  * Start Exe
  *
@@ -190,6 +208,7 @@ void start_kubelet(void) {
     SET_ARG("--image-credential-provider-bin-dir", KUBELET_CREDENTIAL_PROVIDER_BIN_DIR);
   }
 
+  set_hostname_from_file();
   kubelet_pid = start_exe("/bin/kubelet", KUBELET_LOG, kubeletArgs);
 }
 

pkgs/bin/init/src/init.c

@@ -12,23 +12,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-/**
- * Set Hostname From File
- *
- * Checks to see if /etc/hostname exists and contains content - if it
- * does the hostname is updated.
- */
-static void set_hostname_from_file(void) {
-  char hostname[HOST_NAME_MAX];
-  FILE *fp = fopen("/etc/hostname", "r");
-  if (fp) {
-    if (fgets(hostname, HOST_NAME_MAX, fp)) {
-      sethostname(hostname, strlen(hostname));
-    }
-    fclose(fp);
-  }
-}
-
 /**
  * Enable IP Forwarding
  *
@@ -90,7 +73,6 @@ int main(int argc, char **argv) {
   // reasonable to do so. All our other init steps are performed in that
   // three second window.
   bring_if_up("eth0");
-  set_hostname_from_file();
   enable_ip_forwarding();
   start_socket();
   signal(SIGTERM, &soft_shutdown);
@@ -99,14 +81,6 @@ int main(int argc, char **argv) {
   // Now we are finished with our own setup, wait for crio to be ready.
   wait_for_path(CRIO_SOCK);
 
-  if (!fexists(KUBELET_CONFIG)) {
-    start_kubelet();
-    wait_for_path(KUBELET_CONFIG);
-    set_hostname_from_file();
-
-    stop_kubelet();
-  }
-
   start_kubelet();
   run_wait_loop();
 }