Kubernetes Logs & Binaries: Component Troubleshooting Reference

What are important Log and Binary files location in k8s?

Let's categorize the critical file system locations you need to know for operations, debugging, and security auditing. We can divide these into Binaries/Executables, Configuration & State, and Logging Directories.

The locations below primarily reflect standard Linux deployments (like those built with kubeadm), though I will note Windows paths where relevant.

1. Binaries and Executables

These are the static files required to bootstrap and run the node components.

• Core Kubernetes Binaries:
  • Location: /usr/bin/
  • Components: This typically includes kubeadm, kubelet, and kubectl.
  • Context: The kubelet is the primary node agent that must run directly on the host (usually via systemd), while kubectl and kubeadm are CLI tools.
• CNI Plugins (Container Network Interface):
  • Location: /opt/cni/bin/
  • Components: Network binaries like bridge, flannel, calico, or loopback.
  • Context: The container runtime looks here for the executables required to set up pod networking,.
• Container Runtime Interface (CRI) Tools:
  • Location: /usr/bin/ or /usr/local/bin/
  • Components: crictl (the CLI for CRI-compatible runtimes),.

2. Configuration, Certificates, and State

This is the "brain" of the node. These directories contain the identity of the cluster and the definition of what should be running.

• Static Pod Manifests:
  • Location: /etc/kubernetes/manifests
  • Purpose: The kubelet periodically scans this directory. Any YAML file found here is launched as a Static Pod.
  • Engineering Note: In kubeadm clusters, this is where the Control Plane components (API Server, Controller Manager, Scheduler, and sometimes etcd) live.
• PKI and Certificates:
  • Location: /etc/kubernetes/pki
  • Purpose: Contains the Certificate Authority (CA), API server certificates, and service account keys.
  • Security: This directory is highly sensitive. Compromise here equals total cluster compromise.
• Kubeconfig Files:
  • Location: /etc/kubernetes/
  • Files: admin.conf, kubelet.conf, controller-manager.conf, scheduler.conf.
  • Purpose: These define authentication/authorization context for the core components.
• Kubelet State and Config:
  • Location: /var/lib/kubelet
  • Files: config.yaml (downloaded cluster-wide config), kubeadm-flags.env (runtime flags).
• Etcd Data (Database):
  • Location: /var/lib/etcd
  • Purpose: The persistent storage for the etcd key-value store on control plane nodes.

3. Logging Locations

Logging architecture depends heavily on your OS and initialization system (usually systemd).

• Pod/Container Logs:
  • Location: /var/log/pods
  • Mechanism: The container runtime writes stdout/stderr streams here. The kubelet makes these available to kubectl logs.
  • Warning: Do not change this path lightly; many system processes imply this specific path.
• System Component Logs (Systemd):
  • Location: journald
  • Access: Use journalctl -u kubelet or journalctl -u containerd.
  • Context: On modern Linux nodes using systemd, the kubelet and container runtime write to the journal rather than a static file.
• System Component Logs (File-based/Legacy):
  • Location: /var/log/
  • Files: /var/log/kubelet.log, /var/log/kube-apiserver.log, /var/log/kube-scheduler.log,.
  • Context: This is common on systems without systemd or in specific cloud provider configurations.
• Windows Logs:
  • Location: /var/log/
  • Context: Similar to Linux, you may find logs in /var/log/ or via the application log provider.

Summary Table

Component	Path	Description
Manifests	/etc/kubernetes/manifests	Static Pod definitions (Control Plane).
Certificates	/etc/kubernetes/pki	TLS certs and keys (CA, API Server).
Kubeconfigs	/etc/kubernetes/	Auth files for system components.
Pod Logs	/var/log/pods	Stdout/Stderr from running containers.
CNI Binaries	/opt/cni/bin/	Network plugins (e.g., bridge, flannel).
Kubelet	/usr/bin/kubelet	The primary node agent binary.