Filtering log files

As we have explored in this book, one of the most valuable resources for diagnosing issues or troubleshooting is the log files. The log files are always telling the truth and learning about some CLI tools can help us filter data inside the logs and save a lot of time!

In the following, we will explore how to filter logs on OPNsense.

On the CLI, we will change our current directory to the /var/logs path, as we have learned that the logs are stored in this path.

Filtering logs

To have a continuous output of a log file, we can use the tail -f command:

root@bluebox:/var/log # tail -f system/system_`date +%Y%m%d`

Note

The `date +%Y%m%d` command will set the filename to the current date.

grep is one of the most helpful tools to filter data inside log files. We can use it to extract information more clearly:

root@bluebox:/var/log # grep --color -i error system/system_20220305.log

In the preceding example, we filter the word error inside...