How to tail all the log files inside a folder and subfolders?

If all log files doesn't have same extension. You can use following command.

tail -f **/*

This will recursively find all *.log files in current directory and its subfolders and tail them.

find . -type f \( -name "*.log" \) -exec tail -f "$file" {} +

Or shortly with xargs:

find . -name "*.log" | xargs tail -f

To log all the files inside a folder, you can go to the folder and write

tail -f *.log

To add the subfolders to the tailf command, use

tail -f **/*.log

Of course, the regular expression can be improved to match only specific file names.