Batch renaming files on the command line

The default command line application for batch renaming files in Ubuntu 16.04 is called "rename":
rename 's/tk98i_/wt_tk98_/' *.tif
It uses Perl regular expressions with and the s/old/new/ syntax. The example above renames all files with the .tif extensions and replaces the th98i_ expression with wt_tk98_.
Here are some more examples:

BSD and Linux

I am used to the fact that a Linux installer honours a pre-existing install of Windows and offers to setup the computer with a dual-boot option during installation. Vice-versa no Windows installer honours any other pre-exisiting OS. Therefore I was surprised that when I tried to install Ubuntu 16.04 on my PFSense box (FreeBSD), the Ubuntu installer did not even see that a BSD install exists on the drive. I chose the "erase all" option, but when I rebooted after the installer has finished, the system went straight into PFSense without giving me any option to select Ubuntu.