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Monitoring System Hardware

You can monitor system hardware with the following commands and utilities:

  • NVUE
  • decode-syseeprom
  • smond
  • sensors
  • watchdog

NVUE Commands

You can run NVUE commands to monitor your system hardware.

nv show platform hardwareShows platform hardware information on the switch, such as the base MAC address, model and manufacturer, memory, Cumulus Linux release, serial number and system MAC address.
nv show system cpuShows information about the switch CPU, such as the core-count, the model, and the utilization percentage.
nv show platform environmentShows a list of sensors, fans, LEDs, and PSUs on the switch.
nv show platform environment fanShows information about the fans on the switch, such as the minimum, maximum and current speed, the fan state, and the fan direction.
nv show platform environment ledShows information about the LEDs on the switch, such as the LED name and color.
nv show platform environment psuShows information about the PSUs on the switch, such as the PSU name and state.
nv show platform environment sensorShows information about the sensors on the switch, such as the critical, maximum, minimum and current temperature and the current state of the sensor.

The following example shows the nv show platform hardware command output:

cumulus@switch:~$ nv show platform hardware
-------------  -----------------
base-mac       44:38:39:22:01:7A
cpu            n/a              
disk-size      n/a              
manufacturer   Cumulus          
memory         1758728 kB       
model          VX               
part-number    5.8.0            
port-layout    n/a              
product-name   VX               
serial-number  44:38:39:22:01:7a
system-mac     44:38:39:22:01:b1
asic-model     n/a              
asic-vendor    n/a

The following example shows the nv show platform environment fan command output. The airflow direction must be the same for all fans. If Cumulus Linux detects that the fan airflow direction is not uniform, it logs a message in the var/log/syslog file.

cumulus@switch:~$ nv show platform environment fan
Name      Fan Direction  Limit variance  Max Speed  Min Speed  Current Speed (RPM)  Fan State
--------  -------------  --------------  ---------  ---------  -------------------  ---------
Fan1      F2B            15              29000      2500       6000                 ok       
Fan2      F2B            15              29000      2500       6000                 ok       
Fan3      F2B            15              29000      2500       6000                 ok       
Fan4      F2B            15              29000      2500       6000                 ok       
Fan5      F2B            15              29000      2500       6000                 ok       
Fan6      F2B            15              29000      2500       6000                 ok       
PSU1Fan1  F2B            15              29000      2500       6000                 ok       
PSU2Fan1  F2B            15              29000      2500       6000                 ok    

If the airflow direction for all fans is not in the same (front to back or back to front), cooling is suboptimal for the switch, rack, and even the entire data center.

decode-syseeprom Command

Use the decode-syseeprom command to retrieve information about the switch EEPROM. If the EEPROM is writable, you can set values on the EEPROM.

The following is example decode-syseeprom command output. The output is different on different switches:

cumulus@switch:~$ decode-syseeprom
TlvInfo Header:
   Id String:    TlvInfo
   Version:      1
   Total Length: 629
TLV Name             Code Len Value
-------------------- ---- --- -----
Product Name         0x21  64 MSN3700C
Part Number          0x22  20 MSN3700-CSBFO
Serial Number        0x23  24 MT2043X05294
Base MAC Address     0x24   6 1C:34:DA:24:C9:00
Manufacture Date     0x25  19 10/21/2020 20:57:29
Device Version       0x26   1 1
MAC Addresses        0x2A   2 254
Manufacturer         0x2B   8 Mellanox
Vendor Extension     0xFD  52 0x00 0x00 0x81 0x19 0x00 0x2E 0x00 0x02 0x07 0x98 0x00 0x00 0x31 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 0x07 
Platform Name        0x28  64 x86_64-mlnx_msn3700C-r0
ONIE Version         0x29  23 2019.11-5.2.0020-115200
CRC-32               0xFE   4 0x11D0954D
(checksum valid)

The decode-syseeprom command includes the following options:

-h, -helpDisplays the help message and exits.
-aPrints the base MAC address for switch interfaces.
-rPrints the number of MAC addresses allocated for the switch interfaces.
-sSets the EEPROM content (if the EEPROM is writable). You can provide arguments in the command line in a comma separated list in the form <field>=<value>.
  • . , and = are not allowed in field names and values.
  • Any field not specified defaults to the current value.

NVIDIA Spectrum switches do not support this option.
-j, --jsonDisplays JSON output.
-t <target>Prints the target EEPROM information (board, psu2, psu1).
--serial, -ePrints the device serial number.
-mPrints the base MAC address for the management interfaces.
--initClears and initializes the board EEPROM cache.

Run the dmidecode command to retrieve hardware configuration information populated in the BIOS.

Run apt-get to install the lshw program on the switch, which also retrieves hardware configuration information.


The smond service monitors system units like power supply and fan, updates the corresponding LEDs, and logs the change in state. The cpld registers detect changes in system unit state. smond utilizes these registers to read all sources, which determines the health of the unit and updates the system LEDs.

Run the sudo smonctl command to display sensor information for the various system units:

cumulus@switch:~$ sudo smonctl
Board                                             :  OK
Fan                                               :  OK
PSU1                                              :  OK
PSU2                                              :  BAD
Temp1     (Networking ASIC Die Temp Sensor       ):  OK
Temp10    (Right side of the board               ):  OK
Temp2     (Near the CPU (Right)                  ):  OK
Temp3     (Top right corner                      ):  OK
Temp4     (Right side of Networking ASIC         ):  OK
Temp5     (Middle of the board                   ):  OK
Temp6     (P2020 CPU die sensor                  ):  OK
Temp7     (Left side of the board                ):  OK
Temp8     (Left side of the board                ):  OK
Temp9     (Right side of the board               ):  OK

When the switch is not powered on, smonctl shows the PSU status as BAD instead of POWERED OFF or NOT DETECTED. This is a known limitation.

The smonctl command includes the following options:

Option Description
-s <sensor>, --sensor <sensor>Displays data for the specified sensor.
-v, --verboseDisplays detailed hardware sensors data.

The following command example shows detailed information about FAN6 on the switch. The information includes the fan state, the current, minimum, and maximum speed, the limit variance, and the fan direction.

cumulus@switch:~$ smonctl -s FAN6 -v
Fan6(Fan Tray 3 Rear):  OK 
fan:8282 RPM   (max = 25000 RPM, min = 4500 RPM, limit_variance = 15 direction = F2B)

For more information, read man smond and man smonctl.

sensors Command

Run the sensors command to monitor the health of your switch hardware, such as power, temperature and fan speeds. This command executes lm-sensors.

Even though you can use the sensors command to monitor the health of your switch hardware, the smond daemon is the recommended method for monitoring hardware health. See smond Daemon above.

For example:

cumulus@switch:~$ sensors
Adapter: i2c-1-mux (chan_id 0)
temp1:        +39.0 C  (high = +75.0 C, hyst = +25.0 C)

Adapter: i2c-1-mux (chan_id 0)
temp1:        +35.5 C  (high = +75.0 C, hyst = +25.0 C)

Adapter: i2c-1-mux (chan_id 1)
in1:         +11.87 V
in2:         +11.98 V
power1:       12.98 W
curr1:        +1.09 A

Adapter: i2c-1-mux (chan_id 2)
fan1:        13320 RPM  (div = 1)
fan2:        13560 RPM

  • Output from the sensors command varies depending upon the switch.
  • If you only plug in one PSU, the fan is at maximum speed.

The following table shows the sensors command options.

-c --config-fileSpecify a configuration file; use - after -c to read the configuration file from stdin; by default, sensors references the configuration file in /etc/sensors.d/.
-s --setExecute set statements in the configuration file (root only); sensors -s runs one time at boot and applies all the settings to the boot drivers.
-f --fahrenheitShow temperatures in degrees Fahrenheit.
-A --no-adapter
-A --bus-list
Do not show the adapter for each chip.
Generate bus statements for sensors.conf.
-uGenerate raw output.
-jGenerate json output.
-vShow the program version.

Hardware Watchdog

Cumulus Linux includes a simplified version of the wd_keepalive(8) daemon instead of the one in the standard watchdog Debian package. wd_keepalive writes to a file called /dev/watchdog periodically (at least one time per minute) to prevent the switch from resetting. Each write delays the reboot time by another minute. After one minute of inactivity, where wd_keepalive does not write to /dev/watchdog, the switch resets itself.

Cumulus Linux enables the watchdog by default, which starts when you boot the switch (before switchd starts).

To disable the watchdog, disable and stop the wd_keepalive service:

cumulus@switch:~$ sudo systemctl disable wd_keepalive ; systemctl stop wd_keepalive 

You can modify the settings for the watchdog, such as the timeout and the scheduler priority, in the /etc/watchdog.conf configuration file.