What exactly is an ext4 signature and why am I removing it?

Question

I was following the steps from an Ask Ubuntu answer (Increase partition size on which Ubuntu is installed?) to enlarge an Ubuntu VM I have and I'm wondering what is actually being removed here:

Partition #1 contains a ext4 signature

Do you want to remove the signature? [Y]es/[N]o:

I found this definition:

File Signature or Magic Number is a protocol set of constant numerical and text values used to identify file format. In other words, every file type requires a unique signature in order for an operating system to recognize it, classify it and show it to an end user

So files have signatures and file systems have signatures as well? If this is the case would removing the signature just replace the signature with the same value, if I'm just enlarging the VM with the same ext4 type filesystem?

Follow up question: Is Ubuntu asking me permission to delete the signature to make me aware that this will erase an entire partition?

Answer 1

Assuming you follow those directions exactly, you are correct. Gparted is emitting a confirmation, to make sure that you selected the correct partion. For instance, someone intending to delete a swap partition might want to be sure that it is, in fact, a swap partition that is being removed.

If you follow the directions in the guide, the end result will still be working: this message is just a confirmation. However, be sure that your data is backed up, and that you have prepared a rescue disk (such as GRML), which has recovery tools like TestDisk installed.