In the "Notes for linux release 0.01", Torvalds lists the GNU software that is required to run Linux:

This quickly became the most popular adoption of GNU software.

GNU software is freely distributed, but in a different manner from public domain and "freeware" software among personal computer users.

The full text is included with GNU software such as Emacs, and is available on the web.

GAS is often used as the assembler on Linux operating systems in conjunction with other GNU software.

Linux distributions are mostly GNU software, and so they include gawk.

Some of these servers hosted software archives containing early versions of Linux and other GNU software.

This is a common feature of GNU software.

Richard Stallman's insistence on the importance of GNU software is certainly right.

Other kernels like the FreeBSD kernel also work together with GNU software to form a working operating system.