Which type of file system is created by mkfs when it is executed with the block device name only and without any additional parameters?

When the mkfs command is executed with just the block device name and no additional parameters, it defaults to creating an ext2 filesystem. The ext2 filesystem is one of the oldest and most widely used Linux file systems. As a standard choice, it does not include journaling, which makes it simpler and sometimes faster for certain uses, though it lacks some resilience against data corruption compared to its successors.

The other file systems listed are either newer or serve different use cases. XFS, for instance, is a high-performance journaling file system suited for large files and high throughput. VFAT is used for compatibility with FAT file systems, primarily for interoperability with Windows systems. Ext3 is an updated version of ext2 that includes journaling capabilities, so it would require the specification of the -j option to be created with mkfs.

Given that no additional options are specified, the default filesystem created by mkfs in this context is indeed ext2, which aligns with the behavior of historical Linux distributions and the default configuration of many systems.