1. Linux：
Linux是由Linus Torvalds开发的一组类似于Unix的开源操作系统。它是Linux发行版的打包。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。 1991年发布了第一个Linux版本。用于个人计算机的最新Linux版本是5.6(内核)。
2. FreeBSD：
FreeBSD是FreeBSD项目提供的一个免费的开源操作系统。它是基于两个类似Unix的操作系统Berkeley Software Distribution(BSD)和Research Unix设计的。它与Linux操作系统非常相似。它是较早的著名操作系统之一，但是现在与其他操作系统相比，它的使用率有所降低。 FreeBSD的第一个版本于1993年发布。FreeBSD的最新稳定版本是12.1。
Linux和FreeBSD之间的区别：
| 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. |