“rename” is a very handy tool that we can use to rename multiple files on Linux. To change all upper case filenames to lower case just use:
rename 'y/A-Z/a-z/' *
To change filename img_0001.jpg .. img_XXXX.jpg to Urlaub_0001.jpg .. Urlaub_XXXX.jpg just do:
rename 's/^/Urlaub/' img*
To display the manual just type:
man rename
For more “rename” information click here.