Linux is not Unix because

Linux is not Unix because of several reasons:

1. Different Origins: Unix was developed by AT&T's Bell Labs back in the 1960s and 1970s. Linux, on the other hand, was created by Linus Torvalds in 1991 while he was a student at the University of Helsinki.

2. Licensing: Unix operating systems are proprietary with different versions of it being owned by different organizations. Linux, however, is free and open-source software. Anyone can download, modify, and distribute it.

3. System Architecture: Unix and Linux have different system architectures. Unix systems have a monolithic kernel where all OS services run in kernel space. Linux, however, uses a modular kernel, which allows it to add and remove modules from the kernel as needed.

4. User Base: Unix is mainly used in servers, workstations, and mainframes. Linux is used in a much wider range of devices, from personal computers, servers, mobile devices, to embedded systems, and more.

5. Commands: While Linux is Unix-like and they share many similar commands, there are differences in command syntax and default shells. For example, the default shell in Unix is the Bourne shell, while Linux uses the Bourne Again shell.

6. Filesystem hierarchy: Both Unix and Linux use a hierarchical file system structure, but the directory names and organization can be different.

In conclusion, while Linux was inspired by Unix and shares many similarities, it is not Unix due to differences in origin, licensing, system architecture, user base, commands, and filesystem hierarchy.