Android AlarmManager after reboot

I'm not sure if I understand the boot receiver and how to then restart all the alarms.

Just call your code to call setRepeating() (or whatever) on AlarmManager.

For example, in this sample project, PollReceiver is set to receive BOOT_COMPLETED. In onReceive(), it reschedules the alarms:

package com.commonsware.android.schedsvc;

import android.app.AlarmManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.SystemClock;

public class PollReceiver extends BroadcastReceiver {
  private static final int PERIOD=5000;

  @Override
  public void onReceive(Context ctxt, Intent i) {
    scheduleAlarms(ctxt);
  }

  static void scheduleAlarms(Context ctxt) {
    AlarmManager mgr=
        (AlarmManager)ctxt.getSystemService(Context.ALARM_SERVICE);
    Intent i=new Intent(ctxt, ScheduledService.class);
    PendingIntent pi=PendingIntent.getService(ctxt, 0, i, 0);

    mgr.setRepeating(AlarmManager.ELAPSED_REALTIME,
                     SystemClock.elapsedRealtime() + PERIOD, PERIOD, pi);
  }
}