unlock Xperia Neo bootloader on linux
both solutions mentioned by @Izzy and @darknight in comments could work, But I found the easiest way is to replace steps 8,9,10 of the instructions by the following terminal command:

sudo apt-get install android-tools-adb android-tools-fastboot


and then continuing as normal (and of course write fastboot instead of fastboot.exe in steps 15,16).

That saves the trouble of manually downloading and installing flashboot and configuring files and so.