view logs
This is a guide to viewing WeeWX log messages.
In its default configuration, WeeWX sends log messages to the system logging facility. This means that the system is responsible for things like ensuring that running multiple instances of weewxd do not corrupt the log, and that the system is responsible for rotating log files so that they do not fill up the disks.
There are many different system loggers available. For example, linux systems have syslog, rsyslog, syslog-ng, and/or systemd-journald, BSD systems typically have syslog and newsyslog. Most of these save the log messages to file, and the system takes care of rotating the log files so that they do not fill up the local storage. Some can be configured to send the logs to a remote logging server, which can make managing multiple machines much easier, and provides security benefits as well.
This document describes some of the configurations you might encounter when you use the system logging facility.
If you want to change the logging configuration, see the Wiki article about How to customize logging
The system logging facility has different log levels. For example, a message about something that is important but non-fatal might be a WARNING, a message about normal report generation might be INFO, and DEBUG messages will appear if you enable verbose logging. Messages about events that adversely affect WeeWX operation will typically be at the ERROR level. These messages include a mis-configured driver or extension, a failed attempt to upload data, or failure to save data to the database,
When you enable debug in the WeeWX configuration file, this enables many more messages, but at the DEBUG level. These messages can help you diagnose problems with hardware, report generation, and network issues.
In a default, functional WeeWX installation, all of the log messages will be at the INFO level. So if you do not see messages from WeeWX in your system logs, be sure that your system is recording all log levels.
Most Linux systems are configured to record all of the log levels. BSD systems such as FreeBSD and OpenBSD are configured to record only error messages. The article about How to customize logging explains how to change a BSD logging configuration.
On systems that use syslog, when weewxd or any service or extension emits a log message, that message goes to the system's logger. The system then saves the log messages to a file. Some operating systems use /var/log/syslog (Debian, Ubuntu, MacOS), while others use /var/log/messages (Redhat, Fedora, CentOS, Rocky, FreeBSD, OpenBSD). In some configurations, you might see messages from WeeWX in both /var/log/syslog and /var/log/messages.
You can use standard tools such as head, tail, more, or less to view those messages.
Here are some examples:
# look at the last 10 messages
sudo tail -10 /var/log/syslog
# look at the first 20 messages, just from weewxd
sudo grep weewxd /var/log/messages | head -20
# watch all of the messages from weewxd as they arrive (ctrl-c to stop)
sudo tail -f /var/log/messages | grep weewxd
# watch the messages from weectl as they arrive, and save them to a file weectl.log
sudo tail -f /var/log/syslog | grep weectl > ~/weectl.log
# watch messages from every WeeWX process and save them to a file
sudo tail -f /var/log/syslog | grep wee | tee ~/weewx.log
On most modern Linux systems, the sudo is required, since the system logs are visible only to the system administration accounts.
On systems that use systemd, there is a program called systemd-journald that manages some (or all) of the system logging. On some systems that use systemd, there is no syslog - they use systemd-journald exclusively. Others include both syslog and systemd-journald. On systems with systemd-journald, you might be able to use the journalctl tool to view messages from WeeWX.
Here are some examples:
# look at the messages only from the weewx service
sudo journalctl -u weewx
# view all of the message contents, not just the first few words of each line
sudo journalctl -u weewx | more
# view the messages from the weectl utility
sudo journalctl -t weectl
# view messages from both weewxd and weectl
sudo journalctl -t weewxd -t weectl
# view messages from every WeeWX process as they arrive and save to file
sudo journalctl -f -t weewxd -t weectl | tee ~/weewx.log
There is a program called logger that you can use to test the behavior of your system's logging facilities.
# view all of the options to the logger program
man logger
# send a simple message with priority 'info'
logger -p info "this is my first message"
