Description

 

When an EX switch is stuck at db> prompt, capturing information will help in understanding the reason the EX switch crashed and help determine a root cause. This article explains how information can be captured for troubleshooting purposes.

 

Symptoms

 

While booting up an EX switch, it is stuck at db> prompt. How do I recover? What data should I collect if I need a Root Cause Analysis?

 

Solution

 

Perform the following steps:

  1. First, collect the following command outputs from the  db> mode / prompt: 

db> x/s version     
db> alltrace
db> ps
db> show allvms
db> show msgbuf
db> show registers
db> show lock
db> show uma

  1. After the information in Step 1 is collected, enter cont to continue: 

db> cont

Do you get the CLI prompt?

  • No - Continue with Step 3 .

  • Yes - Jump to Step 4 .

  1. Reboot, and try and recover from loader mode ( loader> ). If you do NOT get a loader> prompt, open a case with your technical support representative.

To recover the EX switch from the loader> prompt, reinstall the Junos OS software by performing a  Format Install . If a Root Cause Analysis is required after recovery, perform the steps in KB20569 - [EX/QFX] How to collect logs and files from standalone and Virtual Chassis/VCF devices [juniper.net] .

  1. At the CLI prompt, check to see if there are any core files on the switch with the command show system core-dumps . If there are core dumps, their location will be shown with the aforementioned command. You can copy them to a server by using FTP for further analysis.

 

Modification History

 

  • 2020-02-17: Article reviewed for accuracy; no changes required.

  • 2021-09-13: Article reviewed and summarized, redundant links removed. In case of core-dumps, users no longer need to go to shell to find them.