K3S Sysbox Blog Post #478
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K3S Sysbox Blog Post #478
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Signed-off-by: galal-hussein <[email protected]>
brandond
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Sep 30, 2025
dereknola
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Sep 30, 2025
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| title: Sysbox Runtime With K3S | |||
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| title: Sysbox Runtime With K3S | |
| title: Sysbox Runtime With K3s |
We don't refer to the product as K3S in the docs unless its a ENV_VAR (e.g. INSTALL_K3S_VERSION). Its always K3s when written in docs. k3s is reserved for use in the CLI examples, as the "actual binary" name.
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| The K3s binary bundles all the components needed to run a production-ready, CNCF-conformant Kubernetes cluster including containerd, runc, kubelet, and more. In this post we will discuss how containerd communicates with OCI runtimes and will discuss adding another container runtime (Sysbox) to k3s and how it can be used to run system pods in your environment. |
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| The K3s binary bundles all the components needed to run a production-ready, CNCF-conformant Kubernetes cluster including containerd, runc, kubelet, and more. In this post we will discuss how containerd communicates with OCI runtimes and will discuss adding another container runtime (Sysbox) to k3s and how it can be used to run system pods in your environment. | |
| The K3s binary bundles all the components needed to run a production-ready, CNCF-conformant Kubernetes cluster including containerd, runc, kubelet, and more. In this post we will discuss how containerd communicates with OCI runtimes and will discuss adding another container runtime (Sysbox) to K3s and how it can be used to run system pods in your environment. |
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| [Sysbox](https://github.com/nestybox/sysbox) is an open-source, next-generation container runtime created by Nestybox. Unlike traditional runtimes (such as runc), Sysbox is designed to let you run **system containers**. It primarily leverages **Linux user namespaces** and other features to provide containers that behave more like lightweight virtual machines. | ||
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| This means you can run workloads like Docker, Systemd, containerd, or even k3s inside your pods — all without requiring privileged mode. |
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| This means you can run workloads like Docker, Systemd, containerd, or even k3s inside your pods — all without requiring privileged mode. | |
| This means you can run workloads like Docker, Systemd, containerd, or even K3s inside your pods — all without requiring privileged mode. |
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| In short, Sysbox bridges the gap between application containers and virtual machines, enabling use cases like running Kubernetes-in-Kubernetes (K8s-in-K8s), CI/CD pipelines that need full OS-like environments, or development sandboxes with VM-level isolation but container speed. | ||
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| **Important note**: Currently, Sysbox officially supports **CRI-O** only. CRI-O has native support for Linux user namespaces, which Sysbox relies on. While containerd added user namespace support starting in version v2.0, there was a [bug](https://github.com/nestybox/sysbox/issues/958) in sysbox-runc that prevented it from working properly with Sysbox. |
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| **Important note**: Currently, Sysbox officially supports **CRI-O** only. CRI-O has native support for Linux user namespaces, which Sysbox relies on. While containerd added user namespace support starting in version v2.0, there was a [bug](https://github.com/nestybox/sysbox/issues/958) in sysbox-runc that prevented it from working properly with Sysbox. | |
| :::info | |
| Currently, Sysbox officially supports **CRI-O** only. CRI-O has native support for Linux user namespaces, which Sysbox relies on. While containerd added user namespace support starting in version v2.0, there was a [bug](https://github.com/nestybox/sysbox/issues/958) in sysbox-runc that prevented it from working properly with Sysbox. | |
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Use an admonition.
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| # Running Sysbox-runc With K3S | ||
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| In order to run `sysbox-runc` with k3s you need to have a running k3s cluster, and then you can proceed by installing the latest version of sysbox, However since the fix for containerd support hasn't been yet integrated to sysbox main repo only in `sysbox-runc`, we need to build the binaries from source to get the latest updates. |
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| In order to run `sysbox-runc` with k3s you need to have a running k3s cluster, and then you can proceed by installing the latest version of sysbox, However since the fix for containerd support hasn't been yet integrated to sysbox main repo only in `sysbox-runc`, we need to build the binaries from source to get the latest updates. | |
| In order to run `sysbox-runc` with K3s you need to have a running K3s cluster, and then you can proceed to install the latest version of sysbox, However, since the fix for containerd support hasn't yet been integrated to sysbox main repo only in `sysbox-runc`, we need to build the binaries from source to get the latest updates. |
| - Creating secure developer sandboxes that behave like lightweight VMs. | ||
| - Running system daemons or nested container engines inside pods. | ||
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| While Sysbox is officially supported with CRI-O today, the recent fixes in `sysbox-runc` allow it to run on containerd as well — making it possible to integrate with k3s. The integration is still evolving, but it shows how the container ecosystem is moving beyond traditional app containers toward more flexible "system containers." |
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| While Sysbox is officially supported with CRI-O today, the recent fixes in `sysbox-runc` allow it to run on containerd as well — making it possible to integrate with k3s. The integration is still evolving, but it shows how the container ecosystem is moving beyond traditional app containers toward more flexible "system containers." | |
| While Sysbox is officially supported with CRI-O today, the recent fixes in `sysbox-runc` allow it to run on containerd as well — making it possible to integrate with K3s. The integration is still evolving, but it shows how the container ecosystem is moving beyond traditional app containers toward more flexible "system containers." |
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| While Sysbox is officially supported with CRI-O today, the recent fixes in `sysbox-runc` allow it to run on containerd as well — making it possible to integrate with k3s. The integration is still evolving, but it shows how the container ecosystem is moving beyond traditional app containers toward more flexible "system containers." | ||
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| If you’re experimenting with k3s and want to explore system workloads inside pods, Sysbox provides a compelling way to do so while maintaining Kubernetes-native workflows. No newline at end of file |
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| If you’re experimenting with k3s and want to explore system workloads inside pods, Sysbox provides a compelling way to do so while maintaining Kubernetes-native workflows. | |
| If you’re experimenting with K3s and want to explore system workloads inside pods, Sysbox provides a compelling way to do so while maintaining Kubernetes-native workflows. |
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| Sysbox brings a powerful capability to Kubernetes: the ability to run system-level workloads inside containers with strong isolation, without requiring privileged mode. When combined with k3s, this opens the door to new use cases such as: | ||
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| - Running Kubernetes-in-Kubernetes clusters for virtual clusters (k3k). |
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| - Running Kubernetes-in-Kubernetes clusters for virtual clusters (k3k). | |
| - Running Kubernetes-in-Kubernetes clusters for virtual clusters ([k3k](https://github.com/rancher/k3k)). |
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| ## Conclusion | ||
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| Sysbox brings a powerful capability to Kubernetes: the ability to run system-level workloads inside containers with strong isolation, without requiring privileged mode. When combined with k3s, this opens the door to new use cases such as: |
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| Sysbox brings a powerful capability to Kubernetes: the ability to run system-level workloads inside containers with strong isolation, without requiring privileged mode. When combined with k3s, this opens the door to new use cases such as: | |
| Sysbox brings a powerful capability to Kubernetes: the ability to run system-level workloads inside containers with strong isolation, without requiring privileged mode. When combined with K3s, this opens the door to new use cases such as: |
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| ## Sysbox Runtime | ||
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| [Sysbox](https://github.com/nestybox/sysbox) is an open-source, next-generation container runtime created by Nestybox. Unlike traditional runtimes (such as runc), Sysbox is designed to let you run **system containers**. It primarily leverages **Linux user namespaces** and other features to provide containers that behave more like lightweight virtual machines. |
There was a problem hiding this comment.
Suggested change
| [Sysbox](https://github.com/nestybox/sysbox) is an open-source, next-generation container runtime created by Nestybox. Unlike traditional runtimes (such as runc), Sysbox is designed to let you run **system containers**. It primarily leverages **Linux user namespaces** and other features to provide containers that behave more like lightweight virtual machines. | |
| [Sysbox](https://github.com/nestybox/sysbox) is an open-source, next-generation container runtime created by Nestybox. Unlike traditional runtimes (such as runc), Sysbox is designed to let you run "system containers". It primarily leverages **Linux user namespaces** and other features to provide containers that behave more like lightweight virtual machines. |
To match the tone at the end of the article.
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