Scenario / Goal: You are trying to add a hard drive (or new storage) to a Linux server. You want the drive usable. You attach the drive and use fdisk. Now you want to use mkfs to create a file system on it.
Problem: You are trying to use mkfs.ext4 but you get this error: "mkfs.ext4 no such file or directory while trying to determine filesystem size."
Root cause: Wrong /dev/xxx argument. This error message is misleading.
Use "cat /proc/partitions" to find the potential /dev/sdx options to choose from. Then try your mkfs.ext4 command using a /dev/ item in the results of "cat /proc/partitions". The problem should go away.