Daniel's Tech Blog

Cloud Computing, Cloud Native & Kubernetes

Running Fluent Bit on Azure Linux in Azure Kubernetes Service

In May this year, Microsoft announced the general availability of the Azure Linux support in Azure Kubernetes Service.

-> https://azure.microsoft.com/en-us/updates/generally-available-azure-linux-support-in-aks/?WT.mc_id=AZ-MVP-5000119
-> https://techcommunity.microsoft.com/t5/linux-and-open-source-blog/introducing-the-azure-linux-container-host-for-aks/ba-p/3824101?WT.mc_id=AZ-MVP-5000119

Azure Linux is Microsoft’s Linux distribution of CBL-Mariner.

-> https://github.com/microsoft/CBL-Mariner

You can choose now between using Ubuntu or Azure Linux as the host operating system for your node pools in Azure Kubernetes Service, where Ubuntu is still the default.

Today, we quickly focus on running Fluent Bit on Azure Linux in Azure Kubernetes Service.


In its Azure Kubernetes Service documentation, Microsoft highlighted current limitations when using Azure Linux until September 19, 2023.

Some addons, extensions, and open-source integrations may not be supported yet on Azure Linux. Azure Monitor, Grafana, Helm, Key Vault, and Container Insights are supported.

-> https://learn.microsoft.com/en-us/azure/aks/use-azure-linux?WT.mc_id=AZ-MVP-5000119
-> https://github.com/MicrosoftDocs/azure-docs/commit/54b63b106c932c835f8bf0cc0bb612e774f4d251

That said, they did not explicitly mention Fluent Bit as supported. But Container Insights uses the following open-source tools under the hood: Fluentd, Fluent Bit, and Telegraf.

-> https://github.com/microsoft/Docker-Provider

Hence, Fluent Bit should work without any issues on Azure Linux.


I am running an Azure Kubernetes Service cluster with Kubernetes in version 1.27.3 in my Azure subscription. The Azure Kubernetes Service cluster uses Azure Linux as the host operating system for its node pools.

Azure portal - AKS default node pool

❯ kubectl get nodes -o wide
aks-default-33543087-vmss00000l   Ready    agent   7m24s   v1.27.3    <none>        CBL-Mariner/Linux   containerd://1.6.18
aks-default-33543087-vmss00000m   Ready    agent   7m      v1.27.3    <none>        CBL-Mariner/Linux   containerd://1.6.18
aks-default-33543087-vmss00000n   Ready    agent   7m9s    v1.27.3    <none>        CBL-Mariner/Linux   containerd://1.6.18

My next step is the deployment of Fluent Bit in version 2.1.9 to the cluster by running my deployment script.

./deploy-fluent-bit.sh <resource_group> <log_analytics_workspace>

You can find my example configuration on my GitHub repository.

-> https://github.com/neumanndaniel/kubernetes/tree/master/fluent-bit

After a few seconds, Fluent Bit is up and running on Azure Linux.

Azure portal - AKS Kubernetes resource view

❯ kubectl get pods
fluent-bit-7kdtn   1/1     Running   0          2m30s
fluent-bit-brnmz   1/1     Running   0          2m38s
fluent-bit-v9wjs   1/1     Running   0          2m22s

❯ kubectl logs fluent-bit-7kdtn
Fluent Bit v2.1.9
* Copyright (C) 2015-2022 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2023/09/20 18:47:32] [ info] [fluent bit] version=2.1.9, commit=c625ad7ea4, pid=1
[2023/09/20 18:47:32] [ info] [storage] ver=1.4.0, type=memory+filesystem, sync=normal, checksum=off, max_chunks_up=128
[2023/09/20 18:47:32] [ info] [storage] backlog input plugin: storage_backlog.2
[2023/09/20 18:47:32] [ info] [cmetrics] version=0.6.3
[2023/09/20 18:47:32] [ info] [ctraces ] version=0.3.1
[2023/09/20 18:47:32] [ info] [input:storage_backlog:storage_backlog.2] initializing
[2023/09/20 18:47:32] [ info] [input:storage_backlog:storage_backlog.2] storage_strategy='memory' (memory only)
[2023/09/20 18:47:32] [ info] [input:storage_backlog:storage_backlog.2] queue memory limit: 9.5M
[2023/09/20 18:47:32] [ info] [filter:kubernetes:logs_filter_1] https=1 host= port=10250
[2023/09/20 18:47:32] [ info] [filter:kubernetes:logs_filter_1]  token updated
[2023/09/20 18:47:32] [ info] [filter:kubernetes:logs_filter_1] local POD info OK
[2023/09/20 18:47:32] [ info] [filter:kubernetes:logs_filter_1] testing connectivity with Kubelet...
[2023/09/20 18:47:33] [ info] [filter:kubernetes:logs_filter_1] connectivity OK
[2023/09/20 18:47:33] [ info] [filter:kubernetes:events_filter_1] https=1 host= port=10250
[2023/09/20 18:47:33] [ info] [filter:kubernetes:events_filter_1]  token updated
[2023/09/20 18:47:33] [ info] [filter:kubernetes:events_filter_1] local POD info OK
[2023/09/20 18:47:33] [ info] [filter:kubernetes:events_filter_1] testing connectivity with Kubelet...
[2023/09/20 18:47:33] [ info] [filter:kubernetes:events_filter_1] connectivity OK
[2023/09/20 18:47:33] [ info] [http_server] listen iface= tcp_port=2020
[2023/09/20 18:47:33] [ info] [sp] stream processor started

A few minutes later, we see the ingested log data in Log Analytics, the final proof of a correct working Fluent Bit installation on Azure Linux in Azure Kubernetes Service.

Azure Log Analytics log query


Fluent Bit works out of the box on Azure Linux with the same configuration as on Ubuntu. When you are curious to learn more about Azure Linux, have a look at the following link.

-> https://learn.microsoft.com/en-us/azure/azure-linux/?WT.mc_id=AZ-MVP-5000119



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