I think you would really benefit from reading the " Book " downloadable from here http://tinycorelinux.net/book.html
to learn how TC operates.
BTW, the recommended method to achieve persistence of custom files on subsequent reboots is to add these individual files to your backup.
This is just one form of "persistence" you'll find others in the book
There is a "BackUp/Restore" gui in "ControlPanel" to assist with adding files to /opt/.filetool.lst that you want to keep. Also you can add files to/opt/.xfiletool.lst
for files you wish to exclude from the backup.
Or you may enter
to view available options
Backup is enabled by default. You may need to verify that a backup file exists, if not then create one by first verifying there is a file in filetool.lst to backup then use
a backup file is created in the tce directory, usually named something like "/tce/mydata*.tgz
Then you only need to add custom config files to .filetool.lst followed by running the backup tool to save the files.
You can also use this command to make a quick backup