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This page is part of the debugging series — pages with debugging details for a variety of Ubuntu packages.

Contents

Bug Summary
Understanding your bug and getting more information
Getting debug logs
A Testcase
Netplan

Bug Summary

If a network-manager bug report is about not being able to connect the title or summary should be in the format:

"[CHIPSET] cannot connect to (ENCRYPT_METHOD)"

where the CHIPSET is the wireless driver used and ENCRYPT_METHOD is the encryption method used by your wireless network.

Understanding your bug and getting more information

There is a lot of debugging information available on the GNOME Live wiki: NetworkManager/Debugging.
You can also take a look at Darren Albers' FAQ.
There is additional information on DebuggingNetworkManager/ReasonCodes for disconnection and network changes available.

Getting debug logs

You can then follow developers' intructions on a bug report for the exact command line to use; or run it directly as such.

Getting NetworkManager debug logs

By default, the NetworkManager log level is set to info. You can use nmcli to modify the logging level:

$ sudo nmcli general logging level DEBUG domains ALL

You do not need to restart NetworkManager to begin seeing debug messages logged to journalctl. You can watch the NetworkManager logs:

$ sudo journalctl -f -u NetworkManager

Getting ModemManager debug logs

Manually run with debug enabled:

$ sudo /usr/sbin/ModemManager --debug
$ sudo /usr/sbin/NetworkManager --debug --log-level=DEBUG

Getting wpasupplicant debug logs

Change the log level:

$ sudo wpa_cli log_level debug

You do not need to restart wpa_supplicant to begin seeing debug messages logged to journalctl. You can watch the wpa_supplicant logs:

$ sudo journalctl -f -u wpa_supplicant

Getting a capture of syslog

Mixing and mashing the above is perfectly acceptable as well if you want to see how NetworkManager and other parts of the stack interact together.

In order to understand whats going on and track down issues, its good to have a full log. To do so, capture the complete test case and submit the whole file (don't cut out what you think is important). Please add markers in the log file so the bug triager can easily see what actions the user takes at what point of time (this isn't essential, but helps a lot).

To capture the syslog, do:

$ tail -n0 -f /var/log/syslog > /tmp/syslog

and to stop capturing do Ctrl-C (you will have to type your other commands in an other window or tab)

Adding markers is just like adding new lines with an editor that show the triager what happened at what point of time. You can also do this on the fly as you test with the command logger "[ clicked on wireless network 'ubuntu']" .

Example marker:

Sep  6 08:12:30 ...

[ clicked on wireless network 'ubuntu']

Sep  6 08:12:31 ...
...

Handling 3G / modem issues

Here are a few extra things that are very helpful to add in case of issues with 3G.

The output of udevadm for tty devices, and output of lsusb:

$ udevadm info --query=all --path=/sys/class/tty/... --attribute-walk

$ lsusb

Captive portal

You can check the status from the cli using:

$ nmcli networking connectivity check

Since 1.38, you can set Environment=NM_LOG_CONCHECK=1 in NetworkManager.service and restart the service to get additional debug logging about connectivity checking.

A Testcase

A good testcase is a step by step instruction to reproduce your bug starting with driver unloaded and NetworkManager stopped.

First, stop NetworkManager and unload your driver:

$ sudo systemctl stop NetworkManager
$ sudo modprobe -r DRIVER

Next, load the driver and start NetworkManager:

$ sudo modprobe DRIVER
$ sudo systemctl start NetworkManager

Netplan

A configuration abstraction mechanism has added to NetworkManager as of Ubuntu 23.10, called Netplan. There is a whole library of netplan documentation available. However here is a very basic amount of netplan debugging.

Netplan uses the files in /etc/netplan/*.yaml to generate the running profiles you find at /run/NetworkManager/system-connections/*.nmconnection. If you suspect a feature defined in your /etc/netplan/*.yaml files is not being used, it is a good idea to check that the content matches up.

If you find a netplan bug, please report it here: https://bugs.launchpad.net/netplan/+filebug