title: Not able to save crash dump using kdump
body: <p>I have a VPS server on amazon's AWS Lightsail service.
  I've been testing kdump using the following two commands (to trigger an automatic kernel crash):</p>
  <pre><code># echo 1 &gt; /proc/sys/kernel/sysrq
  # echo c &gt; /proc/sysrq-trigger
  </code></pre>
  <p>The problem is that the system crashed and rebooted, but there's no dump saved.</p>
  <p>Here is a list of checking I've done:</p>
  <pre><code>[centos@server crash]$ systemctl status kdump
  ● kdump.service - Crash recovery kernel arming    
    Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; vendor preset: enabled)    
    Active: active (exited) since Mon 2019-03-18 07:43:34 UTC; 5 days ago   
   Process: 4119 ExecStart=/usr/bin/kdumpctl start (code=exited, status=0/SUCCESS)  
  Main PID: 4119 (code=exited, status=0/SUCCESS)    
    CGroup: /system.slice/kdump.service
  
  Mar 18 07:43:32 ip-.ap-northeast-1.compute.internal systemd[1]: Starting Crash recovery kernel arming...
  Mar 18 07:43:34 ip-.ap-northeast-1.compute.internal kdumpctl[4119]: kexec: loaded kdump kernel
  Mar 18 07:43:34 ip-.ap-northeast-1.compute.internal kdumpctl[4119]: Starting kdump: [OK]
  Mar 18 07:43:34 ip-.ap-northeast-1.compute.internal systemd[1]: Started Crash recovery kernel arming.
  
  
  [centos@server crash]$ dmesg | grep Reserving
  [    0.000000] Reserving 256MB of memory at 368MB for crashkernel (System RAM: 2047MB)
  
  
  [centos@server crash]$ cat /proc/cmdline
  BOOT_IMAGE=/boot/vmlinuz-3.10.0-957.1.3.el7.x86_64 root=UUID=f41e390f-835b-4223-a9bb-9b45984ddf8d ro console=tty0 crashkernel=256M console=ttyS0,115200
  
  [centos@server crash]$ grep -v ^# /etc/kdump.conf
  path /var/crash
  core_collector makedumpfile -l --message-level 1 -d 31
  default reboot
  </code></pre>
  <p>There's no log of the crash in the <code>/var/log/messages</code> indicating any error there might be. So I wonder what I might have missed. Or an AWS Lightsail VPS is not capable of saving a kdump at all...?</p>