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):

# echo 1 > /proc/sys/kernel/sysrq
# echo c > /proc/sysrq-trigger

The problem is that the system crashed and rebooted, but there's no dump saved.

Here is a list of checking I've done:

[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

There's no log of the crash in the /var/log/messages 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...?

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