Open-Source Operating Systems: What Exists, What It Is For, and Which to Learn

An open-source operating system publishes its source code under a licence that lets you study, modify and share it. The main families are Linux distributions (such as Debian, Ubuntu, Fedora, Rocky Linux and AlmaLinux), the BSDs (FreeBSD, OpenBSD, NetBSD), and smaller independent projects such as Haiku. The open-source base of Android, the Android Open Source Project, also belongs here. This guide lists the main options, what each is used for, and which to learn for IT work.

Key takeaways

• Most open-source operating system use is Linux. A Linux distribution bundles the Linux kernel with system tools and a package manager.
• The BSDs are separate operating systems with their own kernels and permissive licences.
• CentOS Linux has reached end of life. CentOS Stream continues, and Rocky Linux and AlmaLinux are RHEL-compatible rebuilds.
• For Linux jobs in India, skills on a Red Hat family system and a Debian family system cover most job descriptions.
• Open source describes the licence. Support and patching depend on who maintains the system and for how long.

What is an open-source operating system?

An operating system manages hardware and runs your programs. It is open source when its source code is published under a licence that lets anyone study, change and redistribute it. Licences differ. The Linux kernel uses the GNU GPL version 2, which requires distributed modified versions to keep their source open, while the BSD systems use permissive licences that allow closed derivatives. The Open Source Definition lists the criteria a licence must meet.

Which open-source operating systems are widely used?

Android's core is open source, although most phones ship with closed Google services on top.

Current releases and support periods

These facts change, so each row links to where the project publishes them. Checked on 18 October 2026.

What happened to CentOS?

CentOS Linux was a free rebuild of Red Hat Enterprise Linux that many companies, including many in India, ran on servers. It has reached end of life and no longer receives security updates. CentOS Stream continues as a development branch just ahead of RHEL. Teams leaving CentOS Linux usually move to RHEL, Rocky Linux or AlmaLinux.

How does open source change security and support?

Open code can be reviewed by many people, but review is not guaranteed. In operations, what matters is who ships patches and for how long. A commercial subscription such as RHEL gives vendor support and certified hardware and software. A community distribution gives you free updates, and you take responsibility for reading advisories and planning upgrades before a release reaches end of life.

Which one should you learn first?

That depends on the job you want. The suggestions below are WebAsha's opinion, based on how Linux job descriptions commonly read:

• System administrator or RHCSA path: a Red Hat family system (RHEL, Rocky Linux or AlmaLinux for practice). The RHCSA exam, EX200, is based on RHEL 10.
• Cloud and DevOps: Ubuntu and Debian are common in cloud servers and container images, so learn both families' package tools, apt and dnf.
• Security: Kali Linux for testing tools, plus a general server distribution so you understand what you are defending.
• Internals or firewalls: FreeBSD or OpenBSD in a virtual machine.

How do you try them safely?

Use a virtual machine in VirtualBox, VMware or KVM and take a snapshot before you experiment. Download ISO images only from the project's official site and verify the checksum and signature published there. For example, on Linux:

sha256sum downloaded-image.iso

Compare the output with the checksum file on the project's download page.

Common mistakes

• Running CentOS Linux in production after its end of life.
• Installing a release that is close to its end of support without checking the dates above.
• Choosing a distribution from a ranking list instead of your goal.
• Assuming open source means no vendor or support plan is needed.
• Switching distributions every week instead of learning one well.

Next steps

If you are starting from zero, the Linux course is a structured path. To see where Linux skills can lead, read how to start a career with Linux. For the Red Hat route, see the RHCSA EX200 course.

Related reading

• The Future of Desktop Operating Systems | AI, Cloud Computing, Security, and Cross-Platform Integration
• What is Linux Operating System and its Evolution and Future
• Embedded Linux Growth: Edge Computing, IoT Devices and RISC-V
• Which OS Is Harder to Protect? Windows, Linux, or Android Compared

References

• Open Source Initiative: The Open Source Definition
• Red Hat Enterprise Linux life cycle
• Ubuntu release cycle
• Debian releases
• Fedora release life cycle
• FreeBSD release information
• CentOS Linux end of life
• Red Hat: EX200 RHCSA exam

Last reviewed: 18 October 2026.