Step 1 - Activate kdump:
If the appliance is no longer responding, you can trigger the kernel crash dump using sysrq key combination either by the local console (keyboard) or serial console.
Before you use sysrq, you must enable this feature in the kernel. Perform this procedure while the system is in a healthy state.

To enable this feature, perform one of the following:

• From a root shell, run the sysctl -w kernel.sysrq=1 command.
  NOTE: This option is NOT persistent after you reboot the appliance.
  1. Connect to MWG using SSH and log on.
  2. Type sysctl -w kernel.sysrq=1 and press Enter. This command enables the temporary feature.
     ​
• Edit sysctl.conf and set the option kernel.sysrq=1.
  NOTE: This option IS persistent after reboot.
  1. Connect to MWG using SSH and log on.
  2. Change directory to cd /etc.
  3. Type vi sysctl.conf and press Enter.
  4. Change the entry kernel.sysrq=0 to kernel.sysrq=1.
  5. Save the changes. Type wq.

Step 2 - Set the destination for the dump
The initially configured partition probably does not contain enough space for the dump to be saved. So, you must change the location where the dump is saved to /opt/crash:

1. Connect to MWG using SSH and log on.
    
2. Create a new directory:
   Type mkdir /opt/crash and press Enter.
    
3. Change the path:
   Type sed -i 's!^path .*!path /opt/crash!' /etc/kdump.conf and press Enter.

NOTES:

• This change is persistent across reboots. No reboot is required to make the change active.
• Make sure you use the commands exactly as written above; no whitespace changes, no unicode characters, no automatic quote corrections.

To trigger the kernel crash dump:
When you see the appliance enter the error state, you can use one of three ways to trigger a kernel crash dump:

• From the serial console:
  Send a break sequence followed by C.
  NOTE: How to send a break depends on the terminal client. It must pull TX line to 0 Volt level for about 250 ms.
   
• From the local console (directly attached keyboard and monitor):
  Press Alt + SysRq + C at the same time.
  NOTE:
  • ​The SysRq key might also be labeled Print, Drucken, or S-Abf. The Alt key might also be labeled Alt Gr.
  • The SysRq key combination does not require a user to be logged in or a shell to be active.
  • To test in advance whether SysRq has been enabled correctly and the key combination works, press Alt + SysRq + H (or break + H on serial). This action prints a SysRq help message.
     
• From the RMM remote console:
  1. Open the Soft Keyboard:
     Select Keyboard, Soft Keyboard and select the Show checkbox. Or, press ALT+S.  
      
  2. In the Keyboard menu of the console window, enable Hold Right Alt Key. 
  3. On the soft keyboard, click the Prt key and then the c key.