How do I know why NetworkManager failed to initiate the VPN connection?

Question

I'm running Arch Linux, and recently updated the whole system.

Now I every time I connects to VPN with nmcli command, if it fails, I couldn't figure out the reason:

NetworkManager[15967]: <info> VPN plugin state changed: starting (3)
NetworkManager[15967]: <info> VPN connection 'XXX' (Connect) reply received.
NetworkManager[15967]: <warn> /sys/devices/virtual/net/ppp0: couldn't determine device driver; ignoring...
NetworkManager[15967]: <warn> VPN plugin failed: 1
NetworkManager[15967]: <warn> VPN plugin failed: 1
NetworkManager[15967]: <warn> VPN plugin failed: 1
NetworkManager[15967]: <info> VPN plugin state changed: stopped (6)
NetworkManager[15967]: <info> VPN plugin state change reason: 0
NetworkManager[15967]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.

Prior to the upgrade, I can see error messages from pppd, e.g "You're already logged in bla bla", now every helpful message is gone.

Any ideas? Why is the connection failed?

Solution

Change the used loglevel in your NetworkManager.conf file

[logging] This section controls NetworkManager's logging. Any settings here are overridden by the --log-level and --log-domains command-line options.

   level=<level>
          One of [ERR, WARN, INFO, DEBUG].  The ERR level logs only critical
          errors.  WARN logs warnings that may reflect operation.  INFO logs
          various  informational messages that are useful for tracking state
          and operations.   DEBUG  enables  verbose  logging  for  debugging
          purposes.   Subsequent  levels  also log all messages from earlier
          levels; thus setting the log level to INFO  also  logs  error  and
          warning messages.

But note this part:

This section controls NetworkManager's logging. Any settings here are overridden by the --log-level and --log-domains command-line options.

Comments

[slm]

Things to try here: wiki.ubuntu.com/DebuggingNetworkManager. May need to be adapted for Arch.

[daisy]

Nope, it's already installed