# Operating Systems

> Overview of Linux distributions and Microsoft Windows for server, container, and AI/GPU workloads, including support lifecycle, EOL dates, and comparison.

---

## Distribution overview

| Distribution | Family | Package manager | Init | Security | Reference platform |
|-------------|--------|----------------|------|----------|-------------------|
| **Ubuntu LTS** | Debian | apt (deb) | systemd | AppArmor | NVIDIA DGX, widest AI/GPU support |
| **Debian** | Debian | apt (deb) | systemd | AppArmor | General-purpose server, stability |
| **RHEL** | Red Hat | dnf (rpm) | systemd | SELinux | Enterprise standard, SAP, Oracle DB |
| **Rocky Linux** | Red Hat | dnf (rpm) | systemd | SELinux | RHEL binary compatible (free) |
| **AlmaLinux** | Red Hat | dnf (rpm) | systemd | SELinux | RHEL binary compatible (free) |
| **SLES** | SUSE | zypper (rpm) | systemd | AppArmor | HPC, SAP, mainframe |
| **OpenSUSE Leap** | SUSE | zypper (rpm) | systemd | AppArmor | Desktop, development |
| **OpenSUSE Tumbleweed** | SUSE | zypper (rpm) | systemd | AppArmor | Rolling release, bleeding edge |
| **Fedora** | Red Hat | dnf (rpm) | systemd | SELinux | Desktop, technology preview |
| **Arch Linux** | Independent | pacman | systemd | — | Rolling, power users |
| **Alpine Linux** | Independent | apk | OpenRC | — | Container image, embedded |
| **Flatcar Container Linux** | Independent | — (image-based) | systemd | — | K8s worker node, minimal footprint |
| **Bottlerocket** | Independent | — (image-based) | systemd | — | AWS K8s, minimal footprint |

---

## Support lifecycle and EOL dates

> **Standard:** base support (bug fixes, security). **LTS/ELS:** extended support (security only).
> ESM = Ubuntu Extended Security Maintenance, EUS = RHEL Extended Update Support, LTSS = SUSE Long Term Service Pack Support.

### Ubuntu LTS

| Version | Release | Standard support | ESM / Ubuntu Pro | Note |
|---------|---------|-----------------|------------------|------|
| **20.04 LTS** (Focal) | 2020-04 | End 2025-04 | End 2030-04 | Last release with Python 2 |
| **22.04 LTS** (Jammy) | 2022-04 | End 2027-04 | End 2032-04 | NVIDIA DGX standard |
| **24.04 LTS** (Noble) | 2024-04 | End 2029-04 | End 2034-04 | Latest GPU/CUDA support |
| **26.04 LTS** (planned) | 2026-04 | End 2031-04 | End 2036-04 | — |

### RHEL

| Version | Release | Full support | Maintenance support | Extended life cycle |
|---------|---------|-------------|-------------------|-------------------|
| **7** | 2014-06 | End 2019-08 | End 2024-06 | End 2028-06 (ELS) |
| **8** | 2019-05 | End 2024-05 | End 2029-05 | End 2034-06 (ELS) |
| **9** | 2022-05 | End 2027-05 | End 2032-05 | End 2037-06 (ELS) |
| **10** (planned) | 2025 | End 2029 | End 2034 | — |

### Rocky Linux / AlmaLinux

| Version | Release | Support until | RHEL compatible | Note |
|---------|---------|-------------|-----------------|------|
| **8** | 2021-06 | 2029-05 | Yes (since RHEL 8.4) | Alma/Rocky |
| **9** | 2022-07 | 2032-05 | Yes (since RHEL 9.0) | Alma/Rocky |

### Debian

| Version | Release | Full support | LTS support | ELTS (paid) |
|---------|---------|-------------|-------------|-------------|
| **11** (Bullseye) | 2021-08 | 2024-08 | End 2026-08 | End 2028-08 |
| **12** (Bookworm) | 2023-06 | 2026-06 | End 2028-06 | End 2030-06 |
| **13** (Trixie) | 2025 (expected) | ~3 years post-release | ~5 years post-release | — |

### SLES

| Version | Release | General support | LTSS | Note |
|---------|---------|---------------|------|------|
| **15 SP3** | 2021-06 | End 2024-12 | End 2027-12 | — |
| **15 SP4** | 2022-06 | End 2025-12 | End 2028-12 | — |
| **15 SP5** | 2023-06 | End 2026-12 | End 2029-12 | Current SP |
| **15 SP6** | 2024-10 | End 2027-12 | End 2030-12 | — |

### Fedora

| Version | Release | EOL | Note |
|---------|---------|-----|------|
| **38** | 2023-04 | 2024-05 | — |
| **39** | 2023-11 | 2024-12 | — |
| **40** | 2024-04 | 2025-05 | — |
| **41** | 2024-11 | 2025-12 | — |

Fedora releases a new version every ~6 months, EOL ~13 months after release. Serves as upstream for RHEL.

### Alpine Linux

| Version | Release | EOL |
|---------|---------|-----|
| **3.18** | 2023-05 | 2025-05 |
| **3.19** | 2023-12 | 2025-12 |
| **3.20** | 2024-05 | 2026-05 |
| **3.21** | 2024-12 | 2026-12 |

---

## Kernel version per distribution

| Distribution | Kernel (default) | Kernel (HWE/enhanced) | Note |
|------------|-----------------|----------------------|------|
| Ubuntu 22.04 LTS | 5.15 (GA) | 6.5+ (HWE) | HWE from 22.04.2 |
| Ubuntu 24.04 LTS | 6.8 | — | — |
| RHEL 8 | 4.18 | — | Backported features |
| RHEL 9 | 5.14 | — | Backported features |
| RHEL 10 | 6.11+ (expected) | — | — |
| Rocky/Alma 8 | 4.18 | — | Same as RHEL 8 |
| Rocky/Alma 9 | 5.14 | — | Same as RHEL 9 |
| Debian 11 | 5.10 | 6.1 (backports) | — |
| Debian 12 | 6.1 | — | — |
| SLES 15 SP5 | 5.14 | — | — |
| SLES 15 SP6 | 6.4 | — | — |
| Fedora 40 | 6.8+ | — | Rolling upstream |
| Alpine 3.20 | 6.6 | — | — |

---

## Use case comparison

| Use case | Recommended distribution | Rationale |
|----------|------------------------|-----------|
| **AI/GPU cluster (DGX)** | Ubuntu 22.04 LTS / DGX OS | NVIDIA standard, CUDA, MLNX_OFED |
| **Enterprise K8s (OpenShift)** | RHEL 9 / RHCOS | Red Hat support, GPU Operator |
| **Vanilla K8s (on-prem)** | Ubuntu 22.04 LTS + Flatcar (workers) | Community support, minimal worker image |
| **HPC cluster (Slurm)** | Rocky Linux 9 / Ubuntu 22.04 | EL ecosystem + Lustre, or Ubuntu |
| **Traditional enterprise DB (Oracle, SAP)** | RHEL 9 / SLES 15 | Vendor certification |
| **Container host** | Ubuntu 22.04 / Alpine | Broad image compatibility / min size |
| **Development / desktop** | Fedora / Ubuntu 24.04 / OpenSUSE Tumbleweed | Latest packages, HW support |
| **Embedded / IoT** | Debian / Alpine / Yocto | Minimal footprint, stability |
| **Edge inference** | Ubuntu (ARM) / NVIDIA JetPack | Jetson, GPU support |
| **Mainframe (IBM z/Arch)** | SLES 15 / RHEL 9 | IBM certification |

---

## Package management comparison

| Feature | apt (Debian/Ubuntu) | dnf (RHEL/Rocky/Alma/Fedora) | zypper (SUSE) | pacman (Arch) | apk (Alpine) |
|---------|--------------------|------------------------------|---------------|---------------|-------------|
| **Package format** | .deb | .rpm | .rpm | .pkg.tar.zst | .apk |
| **Repo management** | /etc/apt/sources.list | /etc/yum.repos.d/ | /etc/zypp/repos.d/ | /etc/pacman.conf | /etc/apk/repositories |
| **Lock file** | — (apt-mark hold) | — (exclude) | — (lock) | — (IgnorePkg) | — |
| **Transactional update** | No | Yes (dnf history) | Yes (zypper history) | No | No |
| **Rollback** | No (manual) | Yes (dnf history rollback) | Yes (snapper + zypper) | No | No |
| **Delta updates** | Yes (apt-xapian) | Yes (deltarpm) | Yes (zsync) | No | No |
| **Version (as of 2025)** | apt 2.7+ | dnf 4.18+ | zypper 1.14+ | pacman 6.1+ | apk 2.14+ |

---

## Security model comparison

| Feature | SELinux (RHEL derivatives) | AppArmor (Ubuntu/Debian/SUSE) |
|---------|--------------------------|-------------------------------|
| **Type** | Mandatory Access Control (MAC) | Mandatory Access Control (MAC) |
| **Labeling** | Context-based (user:role:type) | Path-based (profile per executable) |
| **Configuration** | Policy (modules, booleans) | Profiles (text, in /etc/apparmor.d/) |
| **Modes** | Enforcing / Permissive / Disabled | Enforce / Complain / Disabled |
| **Learning curve** | Steep (complex policies) | Moderate (simpler profiles) |
| **Default in** | RHEL, Rocky, Alma, Fedora | Ubuntu, Debian, SLES, OpenSUSE |
| **Use case** | Enterprise multi-tenant, regulated | General-purpose server, app containment |
| **Container integration** | SELinux labels on container | AppArmor profile on container |

Additional layers:
- **seccomp** — syscall filtering (default in containerd, Docker)
- **Capabilities** — Linux capabilities (drop all except required)
- **cgroups v2** — resource isolation (CPU, memory, IO, PID)
- **User namespaces** — rootless containers (Podman, Docker rootless)

---

## Recommended migration path for EOL distributions

| From | To | Recommended approach |
|------|-----|---------------------|
| Ubuntu 20.04 (EOL 2025) | Ubuntu 22.04 or 24.04 | `do-release-upgrade` or fresh install |
| RHEL 7 (EOL 2024) | RHEL 8 or 9 | `leapp` upgrade, or fresh install |
| Rocky/Alma 8 | Rocky/Alma 9 | `dnf upgrade --releasever=9` |
| Debian 11 (EOL LTS 2026) | Debian 12 | `apt full-upgrade` + new sources.list |
| SLES 15 SP4 (EOL 2025) | SLES 15 SP6 | `zypper migration` |
| Fedora 40 (EOL 2025) | Fedora 42+ | `dnf system-upgrade` |

---

## Microsoft Windows

### Windows Server — editions

| Edition | Price (approx) | Core limits | VM rights | Use case |
|---------|---------------|-------------|-----------|----------|
| **Datacenter** | ~$6,155 (2025) | Unlimited | Unlimited Windows VMs per host | Virtualization, SDDC, S2D, HCI |
| **Standard** | ~$1,069 (2025) | 2 CPU, unlimited cores | 2 Windows VMs + Hyper-V host | General server, AD, file server |
| **Essentials** | ~$501 (2025) | 1 CPU, max 10 users | — | Small business (≤25 users) |
| **Azure Edition** | Pay-as-you-go | Per Azure VM | Per Azure | Azure-only, hotpatching |

Licensing: Windows Server Standard and Datacenter are licensed **per core** (min 16 core/server + 8 core/VM).

### Windows Server — support lifecycle

> **Mainstream:** regular updates (bug fixes, security, features). **Extended:** security updates only (free).
> **ESU:** Extended Security Updates (paid tier, ~$45–300/core/year).

| Version | Release | Mainstream support | Extended support | ESU | Note |
|---------|---------|------------------|-----------------|-----|------|
| **2012 R2** | 2013-11 | 2018-10 | 2023-10 | End 2026-10 (year 3) | ESU paid, final year |
| **2016** | 2016-10 | 2022-01 | 2027-01 | — | Last with Desktop Experience |
| **2019** | 2019-01 | 2024-01 | 2029-01 | — | Last with Nano Server (1803 only) |
| **2022** | 2021-09 | 2026-10 | 2031-10 | — | Current, TPM 2.0, Credential Guard |
| **2025** | 2024-11 | 2029-10 | 2034-10 | — | Hotpatching, PowerShell 7, SMB over QUIC |

### Windows Server — version vs edition feature grid

| Version | Hyper-V | Storage Spaces Direct | Software-defined networking | Containers | GPU DDA / vGPU | WSL2 |
|---------|---------|---------------------|---------------------------|------------|---------------|------|
| 2016 Standard | Yes | No (DC only) | No (DC only) | Windows only | Yes | No |
| 2016 Datacenter | Yes | Yes | Yes | Windows | Yes | No |
| 2019 Standard | Yes | No | No | Windows | Yes | No |
| 2019 Datacenter | Yes | Yes | Yes | Windows | Yes | No |
| 2022 Standard | Yes | No | No | Windows + Linux | Yes | No |
| 2022 Datacenter | Yes | Yes | Yes | Windows + Linux (2022.2+) | Yes | No |
| 2025 Datacenter | Yes | Yes | Yes | Windows + Linux | Yes | Yes |

### Windows Desktop — support lifecycle

> **E = Enterprise, Pro = Professional, Home = Consumer**
> LTSC = Long Term Servicing Channel (stable, no feature updates)

| Version | Release | EOL (Home/Pro) | EOL (Enterprise) | LTSC EOL | Note |
|---------|---------|---------------|-----------------|----------|------|
| **10 21H2** | 2021-11 | — | 2024-06 | — |
| **10 22H2** | 2022-10 | 2025-10 | 2025-10 | — | Final Windows 10 |
| **10 LTSC 2021** | 2021-11 | — | — | 2032-01 | IoT Enterprise LTSC |
| **11 22H2** | 2022-09 | 2024-10 | 2025-10 | — |
| **11 23H2** | 2023-10 | 2025-11 | 2026-11 | — |
| **11 24H2** | 2024-10 | 2026-10 | 2027-10 | — | First with Recall, Copilot+ |
| **11 LTSC 2024** | 2024-10 | — | — | 2029-10 | Enterprise LTSC |

Windows 10 support **ended 2025-10-14** — last version with classic Control Panel.

### Windows vs Linux — comparison

| Feature | Windows Server | RHEL / Ubuntu |
|---------|---------------|---------------|
| **License (server)** | $500–6,000 (per core) + CAL | $0–800 (per node subscription) |
| **License (desktop)** | $100–200 (OEM/retail) | Free |
| **Support cost** | Included in license (SA/ESU) | $200–1,300/node/year (RHEL) |
| **Package management** | MSI, AppX, winget, NuGet | APT, DNF, Zypper |
| **Package count** | ~10,000 (chocolatey) | ~60,000+ (Ubuntu repo) |
| **Desktop GUI** | Windows Shell (mandatory) | Optional (GNOME, KDE, XFCE…) |
| **Server GUI** | Windows Shell (core-only since 2022) | CLI-only (standard) |
| **Kernel** | NT hybrid kernel (kernel-mode Win32) | Monolithic Linux kernel |
| **Device support** | OEM driver model (WHQL) | Open source + vendor drivers |
| **Container types** | Windows + Linux (WSL2) | Linux (Docker, Podman, containerd) |
| **Container registry** | Docker Hub, ACR, Nexus | Docker Hub, Quay, GHCR, Nexus… |
| **Container image size** | ~4–8 GB (Windows Server Core) | ~100 MB – 1 GB (Alpine/Ubuntu) |
| **GPU passthrough** | DDA (Discrete Device Assignment) | GPU Direct, VFIO, SR-IOV |
| **AI/ML support** | WSL2 (CUDA), Azure ML | Native CUDA, ROCm, oneAPI |
| **CUDA support** | Yes (via WSL2 or Docker) | Native (nvidia-container-toolkit) |
| **Orchestration** | AD / GPO / SCCM / WAC | Ansible, Puppet, Salt, Foreman |
| **RBAC/AAA** | Active Directory (+ Kerberos) | LDAP, FreeIPA, SSSD, AD |
| **Remote management** | RDP, WinRM, PowerShell Remoting | SSH, Cockpit, Webmin |
| **Filesystem** | NTFS, ReFS, CSVFS | ext4, XFS, Btrfs, ZFS |
| **Max file system size** | 256 TB (NTFS), 1.2 YB (ReFS) | 1 EB (XFS), 16 EB (ZFS) |
| **Hypervisor** | Hyper-V (Type 1) | KVM (Type 2-like), Xen |
| **Dynamic memory** | Hyper-V Dynamic Memory | KSM, virtio-balloon (KVM) |
| **Live migration** | Hyper-V Live Migration | KVM Live Migration, vMotion |

### Windows specific features

| Feature | Description | Linux alternative |
|---------|------------|-------------------|
| **Active Directory** | Identity, auth, GPO, DNS, DHCP | FreeIPA, Samba AD DC, 389-ds, SSSD |
| **Group Policy** | Central desktop/server configuration | Ansible, Puppet, Salt (agent-based) |
| **Hyper-V + S2D** | Hyper-converged storage and virtualization (HCI) | Proxmox Ceph / oVirt + Gluster |
| **Failover Clustering** | Cluster-aware apps (SQL, File Server) | Pacemaker + Corosync + DRBD |
| **IIS** | Web server, ASP.NET host | Nginx, Apache (.NET host possible) |
| **PowerShell** | Scripting, Desired State Configuration | Bash, Python, Ansible |
| **Windows Admin Center** | GUI management | Cockpit, Webmin |
| **BitLocker** | Full disk encryption | LUKS + cryptsetup |
| **Windows Defender** | Antivirus + EDR | ClamAV, Wazuh, Osquery |
| **SQL Server** | Relational database | PostgreSQL, MySQL, MariaDB |

### Recommended OS per use case (including Windows)

| Use case | OS | Rationale |
|----------|-----|-------|
| **Active Directory / GPO / hybrid ID** | Windows Server 2022/2025 | AD is Windows-only |
| **SQL Server (failover cluster)** | Windows Server Datacenter + SQL EE | Always On FCI, ReFS |
| **Exchange / SharePoint** | Windows Server 2022 | Windows-only |
| **Enterprise desktop management** | Windows 11 Enterprise + Intune/SCCM | GPO, AD, enterprise MDM |
| **.NET / ASP.NET apps** | Windows Server / Linux (.NET Core) | .NET 6+ runs on Linux |
| **HCI (Microsoft stack)** | Windows Server Datacenter + S2D + Hyper-V | Azure Stack HCI |
| **Virtualization (mixed workload)** | Windows Server Datacenter (Hyper-V) | Linux + Windows VMs under one |
| **AI/GPU inference** | Linux (Ubuntu) + CUDA | NVIDIA optimal; WSL2 alternative |
| **Container orchestration (Windows nodes)** | Windows Server 2022/2025 + containerd | Windows Pods in AKS on-prem |
| **Tier 2 apps / web / API** | Ubuntu or RHEL (Linux) | Lower TCO, smaller footprint |

### Windows Server migration paths

| From | To | Recommended approach |
|------|-----|---------------------|
| Windows Server 2012 R2 (EOL 2023) | Windows Server 2022/2025 | In-place upgrade or fresh + migration |
| Windows Server 2016 (EOL 2027) | Windows Server 2022/2025 | In-place upgrade or fresh |
| Windows Server 2019 | Windows Server 2022/2025 | In-place upgrade (`Setup.exe /auto upgrade`) |
| Windows Server 2022 | Windows Server 2025 | In-place upgrade or fresh |
| Windows Server → Cloud | Azure VM / Azure Stack HCI | Azure Migrate, Storage Migration Service |
| Windows Server → Linux | Ubuntu / RHEL (re-platform) | Migrate app to .NET Core or alternative |

### Windows — API and operational limits

| Limit | Windows Server | Windows Desktop |
|-------|---------------|----------------|
| **Max RAM** | 24 TB (2025 Datacenter) | 2 TB (Pro/Enterprise), 128 GB (Home) |
| **Max CPU sockets** | 64 (Datacenter), 2 (Standard) | 2 |
| **Max CPU cores** | Unlimited | 128 (Pro), 64 (Home) |
| **Max file size (NTFS)** | 256 TB | 256 TB |
| **Max file size (ReFS)** | 18.4 EB (2025) | — |
| **Max volume size (NTFS)** | 256 TB | 256 TB |
| **Max volume size (ReFS)** | 1.2 YB (theoretical) | — |
| **Max dedup volume** | 64 TB (Data Deduplication) | — |
| **Max cluster nodes** | 64 (Failover Cluster) | — |
| **Max VM per host** | Unlimited (Datacenter) | — |
| **VM memory per VM** | 12 TB (2022+) | — |
| **VM vCPU per VM** | 240 (2022+) | — |
| **Concurrent RDP** | 2 (admin), 200+ (RDS CAL) | 1 (Home), more (RDP host) |
| **PowerShell Remoting** | Unlimited (WinRM) | Yes (WinRM) |

---

## Related

- [AI-INFRASTRUCTURE.en.md](AI-INFRASTRUCTURE.en.md) — OS for AI workloads, GPU drivers, kernel parameters
- [KUBERNETES.en.md](KUBERNETES.en.md) — container runtime, orchestration
- [HYPERVISORS.en.md](HYPERVISORS.en.md) — hypervisors, VM host OS
- [DATACENTERS.en.md](DATACENTERS.en.md) — DC layout, HW platforms

## Sources

Links, books, and standards: [sources/infrastructure/sources.en.md](sources/infrastructure/sources.en.md)

*Last revision: 2026-06-18*