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Cumulus Linux

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Monitoring and Troubleshooting

This chapter introduces the basics for monitoring and troubleshooting Cumulus Linux.

Serial Console

Use the serial console to debug issues if you reboot the switch often or if you do not have a reliable network connection.

The default serial console baud rate is 115200, which is the baud rate ONIE uses.

Configure the Serial Console

On x86 switches, you configure serial console baud rate by editing grub.

Incorrect configuration settings in grub cause the switch to be inaccessible through the console. Review grub changes before you implement them.

The valid values for the baud rate are:

  • 300
  • 600
  • 1200
  • 2400
  • 4800
  • 9600
  • 19200
  • 38400
  • 115200

To change the serial console baud rate:

  1. Edit the /etc/default/grub file and provide a valid value for the --speed and console variables:

    GRUB_SERIAL_COMMAND="serial --port=0x2f8 --speed=115200 --word=8 --parity=no --stop=1"
GRUB_CMDLINE_LINUX="console=ttyS1,115200n8 cl_platform=accton_as5712_54x"

  2. After you save your changes to the grub configuration, type the following at the command prompt:

    cumulus@switch:~$ update-grub

  3. If you plan on accessing the switch BIOS over the serial console, you need to update the baud rate in the switch BIOS. For more information, see this knowledge base article.

  4. Reboot the switch.

Change the Console Log Level

By default, the console prints all log messages except debug messages. To tune console logging to be less verbose so that certain levels of messages do not print, run the dmesg -n <level> command, where the log levels are:

Level Description
0 Emergency messages (the system is about to crash or is unstable).
1 Serious conditions; you must take action immediately.
2 Critical conditions (serious hardware or software failures).
3 Error conditions (often used by drivers to indicate difficulties with the hardware).
4 Warning messages (nothing serious but might indicate problems).
5 Message notifications for many conditions, including security events.
6 Informational messages.
7 Debug messages.

Only messages with a value lower than the level specified print to the console. For example, if you specify level 3, only level 2 (critical conditions), level 1 (serious conditions), and level 0 (emergency messages) print to the console:

cumulus@switch:~$ sudo dmesg -n 3

You can also run dmesg --console-level <level> command, where the log levels are emerg, alert, crit, err, warn, notice, info, or debug. For example, to print critical conditions, run the following command:

cumulus@switch:~$ sudo dmesg --console-level crit

The dmesg command applies until the next reboot.

For more details about the dmesg command, run man dmesg.

Show System Information

Cumulus Linux provides commands to obtain system information and to show the version of Cumulus Linux you are running. Use these commands when performing system diagnostics, troubleshooting performance, or submitting a support request.

To show information about the version of Cumulus Linux running on the switch, run the nv show system command:

cumulus@switch:~$ nv show system
            operational          applied
-----------  -------------------  -------
hostname     leaf01                
uptime       0:02:50                     
timezone     Etc/UTC                     
maintenance                              
  mode       disabled                    
  ports      enabled

To show system memory information in bytes, run the nv show system memory command:

cumulus@switch:~$ nv show system memory
Type      Buffers     Cache        Free         Total         Used         Utilization
--------  ----------  -----------  -----------  ------------  -----------  -----------
Physical  81661952 B  571834368 B  373276672 B  1813528576 B  786755584 B  79.4%
Swap                               0 B          0 B           0 B          0.0%

To show system CPU information, run the nv show system cpu command:

cumulus@switch:~$ nv show system cpu
             operational                  
-----------  -----------------------------
model        QEMU Virtual CPU version 2.5+
core-count   1                            
utilization  0.3%

To show general information about the switch, run the nv show platform command:

cumulus@switch:~$ nv show platform
              operational                            
------------  ---------------------------------------
system-mac    44:38:39:22:01:b1                      
manufacturer  Accton                                 
cpu           x86_64 QEMU Virtual CPU version 2.5+ x1
memory        1751856 kB                             
disk-size     n/a                                    
port-layout   n/a                                    
asic-model    n/a                                    
system-uuid   a6bfbd6d-70ac-426f-b46d-3743e16e1f4b

Diagnostics Using a cl-support File

You can generate a single export cl-support file that contains various details about switch configuration, and is useful for remote debugging and troubleshooting.

Generate a cl-support file to investigate issues before you submit a support request. You can either run the NVUE nv action generate system tech-support command or the Linux sudo cl-support command:

cumulus@switch:~$ nv action generate system tech-support
...

For more information, refer to Understanding the cl-support Output File.

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