I'm looking for a linux command to search a folder directory and it's subfolders for a file by name and replace all of them with a copy of another file. Any idea?
Assuming you have the replacement file in your home directory (~), you can use find to do the replacing. This will find all boom.txt files and replace them with the replace.txt file (keeping the boom.txt name).
find . -name "boom.txt" -exec cp ~/replace.txt {} \;
Adding to the answer by user1683793, the following command can also be an alternative for the copy and replace. This command is verified on Mintty(Windows 10).
find . -name "boom.txt" -print -exec cp ~/replace.txt {} \;