This post will show how to change permission for directories & files via command line on Linux based operating system.
Changing permission for single directory
chmod 777 directory-name/
Changing permission for single file
chmod 644 file-name.txt
Change permission recursively
This command will also change all subfolder & files in directory name images/.
chmod -R 755 images/
Change only files in a directory & subdirectory
find . -type f -exec chmod 644 {} +
Change only directories in a directory & subdirectory
find . -type d -exec chmod 755 {} +