x86_64

View documentation for the original command

$ tldr setarch

x86_64 is not a standalone executable command. It is an architecture identifier reported by system information tools. To query the system's architecture, use commands like:

uname [OPTION]...
arch

uname -m / --machine
    Prints the machine hardware name, which for 64-bit x86 systems is typically `x86_64`.

uname -a / --all
    Prints all system information, including the machine hardware name (e.g., `x86_64`).

arch
    A simplified command that is equivalent to `uname -m` and prints the machine architecture name (e.g., `x86_64`). This command takes no options.

The x86_64 identifier refers to the 64-bit extension of the x86 instruction set architecture (ISA), originally developed by AMD (known as AMD64) and later adopted by Intel (Intel 64). It is the predominant architecture for modern personal computers, servers, and workstations running Linux.

Unlike the earlier 32-bit x86 (often referred to as i386, i486, i586, i686), x86_64 provides a 64-bit virtual address space, allowing systems to utilize significantly more than 4GB of RAM directly. It also introduces additional general-purpose registers and expands the size of existing registers, leading to improved performance for many applications. When you see 'x86_64' on a Linux system, it indicates that the kernel and user-space programs are compiled for and running on this 64-bit architecture, taking full advantage of its capabilities.

While x86_64 itself is not a directly executable command, it is the standard output for commands like `uname -m` or `arch` on compatible systems, serving as a critical piece of system information.

x86_64 is an architecture identifier, not a directly callable command. Attempting to execute `x86_64` as a command will result in a 'command not found' error. It strictly refers to the underlying hardware and the compilation target for software. System administrators and developers use this identifier to ensure software compatibility and optimize performance.

64-bit Registers: Expands general-purpose registers (GPRs) to 64 bits and doubles their count from 8 to 16.

Larger Virtual Address Space: Enables applications to access far more than 4GB of memory, overcoming the 32-bit memory limit.

RIP-Relative Addressing: Improves position-independent code (PIC) generation, crucial for shared libraries, making code more efficient.

No Segmentation (for flat memory model): While segmentation is technically present for compatibility, it's largely unused in modern 64-bit operating systems like Linux, which primarily operate with a flat memory model for simplicity and performance.

On various Linux systems, you might encounter other terms referring to the x86_64 architecture, such as amd64 (especially prevalent in Debian/Ubuntu and some BSD contexts) or Intel64. However, x86_64 is the most universally accepted and platform-agnostic identifier for this architecture across the Linux ecosystem.

The x86_64 architecture originated from AMD's development of AMD64 (also known as x86-64) in the early 2000s, extending the existing 32-bit x86 instruction set. Intel later adopted a compatible instruction set, initially calling it EM64T or IA-32e, now commonly referred to as Intel 64. These extensions allowed for 64-bit computing while maintaining backward compatibility with 32-bit x86 software. Linux distributions rapidly adopted x86_64, making it the default and most widely supported architecture for servers and desktop systems due to its significant performance benefits and ability to address large amounts of memory.

uname(1), arch(1), lscpu(1), file(1)