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[MX/PTX] How to collect vmhost coredumps from Next Generation Routing Engine (NG-RE)



Article ID: KB32864 KB Last Updated: 13 Mar 2020Version: 2.0

This article describes how to collect vmhost core files from both Junos OS VM and Linux based host (VMHost) in a Next Generation Routing Engine (NG-RE) hardware.


NG-RE is a the RE model sharing common infrastructure for multiple platforms such as MX and PTX.

NG-RE models:

  • RE-S-X6-64G: 6-core Haswell CPU, Wellsburg PCH based routing engine with 64GB DRAM and 2x 64GB SSD storage for MX240/MX480/MX960
  • REMX2K-X8-64G: 8-core Haswell CPU, Wellsburg PCH based routing engine with 64GB DRAM and 2x 64GB SSD storage for MX2020 and MX2010
  • RE-PTX-X8-64G/CB2-PTX: 8-core Haswell CPU, Wellsburg PCH based routing engine with 64GB DRAM and 2x 64GB SSD storage for PTX5K

The NG-RE has a virtualized architecture where Junos OS runs as a virtual machine over a Linux based host (VMHost). When the system boots, Junos OS is automatically launched. At the end of the boot, a login prompt is seen. The NG-RE is based on the popular hypervisor/emulator combination of kvm/qemu.

Junos OS is the only VM operating in the administrative context, although the scope is available for expansion with other VMs in the future.

Refer to the Next Generation Routing Engine Technical Introduction​ for more details.

In NG-RE, there are two levels of coredumps to be collected for JTAC analysis:

  1. Junos OS VM 
  2. Linux based host (VMHost)

Steps for collecting 'vmhost' coredumps:

1. Check if any crashes occurred on the vmhost:

user@host> show vmhost crash
Compute cluster: cluster1-re-cc
Compute node: cluster1-re-cn                  
   Crash Info
   total 0  <<< 0 means there is no crashes in vmhost
2. If there are any vmhost coredumps, copy them from /var/crash on the vmhost using these steps:

a. Login to shell:

labroot> start shell;
% su

b. Login to host:

root@:/var/home/lab # vhclient -s     
Last login: Wed Mar  1 19:34:22 CST 2017 from local-node on pts/1

c. Check if there is a vmhost core file:

vmhost# ls /var/crash

d. Copy the core file to Junos /var/tmp:

request vmhost file-copy crash from-jnode <core-node-xxx.0.tgz> to-vjunos /var/tmp/<core-node-xxx.0.tgz>


Now the files can be directly copied from Routing Engine to any local host using FTP, SCP, JWEB, or mounted USB.

Note: FTP, SSH and HTTP are configured under the system services stanza.

Modification History:

2020-03-12: Added related link to Next Generation Routing Engine Technical Introduction​.

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