chmod Recursive permission change (i.e. in the directory and its sub-directories)

If you have a folder with a lot of files and sub-folders inside it and you want to change permission on all the files, then you should run chmod command(changing permission to xxx) with a -R at the end.

chmod -R 777 (folder name)

in case you got the error that you do not have permission, you have to login as root(su command and then password)at Ubuntu run :

sudo chmod -R 777 (folder name)