1. Linux：
Linux 是一组开源的类 Unix 操作系统，由 Linus Torvalds 开发。它是一个打包的 Linux 发行版。一些最常用的 Linux 发行版是 Debian、Fedora 和 Ubuntu。它基本上是用C语言和汇编语言编写的。 Linux 中使用的内核是 Monolithic 内核。 Linux 发行版的目标系统是云计算、嵌入式系统、移动设备、个人计算机、服务器、大型计算机和超级计算机。 Linux 的第一个版本于 1991 年推出。用于个人计算机的 Linux 的最新版本是 5.6(内核)。
2. FreeBSD：
FreeBSD 是 FreeBSD 项目提供的免费开源操作系统。它是在两个类 Unix 操作系统 Berkeley Software Distribution (BSD) 和 Research Unix 的基础上设计的。它与 Linux 操作系统非常相似。它是早期著名的操作系统之一，但与其他操作系统相比，现在使用较少。 FreeBSD 的第一个版本于 1993 年推出。FreeBSD 的最新稳定版本是 12.1。
Linux 和 FreeBSD 的区别：
| LINUX | FREEBSD |
|---|---|
| It was developed by Linus Torvalds. | It was developed by The FreeBSD Project. |
| It was launched in 1991. | It was launched in 1993. |
| It is designed for personal computers of all companies. | It is not designed for personal computers. |
| Its target system types are embedded systems, mobile devices, personal computers, servers, mainframe computers and supercomputers. | Its target system types are server, workstation, NAS and embedded systems. |
| Computer architectures supported by Linux are IA-32, x86-64, ARM, PowerPC and SPARC. | Computer architectures supported by FreeBSD are IA-32, x86-64, ARM, MIPS and PowerPC. |
| Kernel used in Linux is Monolithic. | Its kernel type is Monolithic with modules. |
| Its package management depends on the distribution. | Its package management is Port collections/packages. |
| Its native APIs are LINUX/POSIX. | Its native APIs are BSD/POSIX. |
| The file systems supported by Linux are ext2, ext3, ext4, btrfs, ReiserFS, FAT, ISO 9660, UDF and NFS. | The file systems supported by FreeBSD are UFS2, ZFS, ext2, ext3, FAT, ISO 9660, UDF and NFS. |
| It has preferred license of GNU GPLv2 (kernel). | It has preferred license of BSD. |
| The non-native APIs supported through its subsystems are Mono, Java, Win16 and Win32. | The non-native APIs supported through its subsystems are Mono, Java, Win16, Win32 and Linux. |