rancher-docs/versioned_docs/version-2.12/troubleshooting/kubernetes-components/troubleshooting-etcd-nodes.md at 42a6a3d2fb0e6b9dcc1f48fc3fb1620008caaa47

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Manuel Simón Nóvoa 64269bea22 Docs: Migrate etcd troubleshooting guide from RKE/Docker to RKE2/K3s/containerd

- Updates `troubleshooting-etcd-nodes.md` to replace Docker-based commands with `crictl` and `etcdctl` for RKE2 and K3s.
- Replaces `curl` connectivity checks with `openssl s_client` to support etcd 3.5+ gRPC requirements and isolate transport layer testing.
- Adds prerequisites section with necessary environment exports.
- Updates all `etcdctl` commands to use explicit inline certificate paths for RKE2 and K3s.
- Replaces shell-dependent container commands with host-side processing to support distroless images.
- Updates log level configuration instructions for RKE2/K3s config files.

2026-03-23 12:25:51 +01:00

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title

title
Troubleshooting etcd Nodes

This section contains commands and tips for troubleshooting nodes with the etcd role in RKE2 and K3s clusters.

Prerequisites

As RKE2 and K3s rely on containerd as the container runtime, crictl replaces Docker for container management. Before proceeding with the troubleshooting commands, configure your environment by exporting the following variables:

RKE2

export PATH=$PATH:/var/lib/rancher/rke2/bin/
export CRI_CONFIG_FILE=/var/lib/rancher/rke2/agent/etc/crictl.yaml
etcdcontainer=$(crictl ps --name etcd --quiet)

K3s

⚠️ Warning

K3s does not include etcdctl in the system PATH. If you need to perform etcd troubleshooting on a K3s cluster, you may need to install it or locate it within the K3s data directory.

export PATH=$PATH:/usr/local/bin
export CRI_CONFIG_FILE=/var/lib/rancher/k3s/agent/etc/crictl.yaml

Checking if the etcd Container is Running

RKE2: The container for etcd should be in the Running state.

crictl ps --name etcd

Example output:

CONTAINER           IMAGE               CREATED             STATE               NAME                ATTEMPT             POD ID              POD                 NAMESPACE
f1e289d202ed0       11ad16872a9cf       58 minutes ago      Running             etcd                0                   7b56aab8204ea       etcd-cluster1     kube-system

K3s: Etcd runs as an embedded process in the K3s service. Check the service status:

systemctl status k3s

etcd Logging

The logs can contain information on what the problem could be.

RKE2:

crictl logs $etcdcontainer

K3s:

journalctl -u k3s | grep -i etcd

Log	Explanation
`health check for peer xxx could not connect: dial tcp IP:2380: getsockopt: connection refused`	A connection to the address shown on port 2380 cannot be established. Check if the etcd container is running on the host with the address shown.
`xxx is starting a new election at term x`	The etcd cluster has lost its quorum and is trying to establish a new leader. This can happen when the majority of the nodes running etcd go down/unreachable.
`connection error: desc = "transport: Error while dialing dial tcp 0.0.0.0:2379: i/o timeout"; Reconnecting to {0.0.0.0:2379 0 <nil>}`	The host firewall is preventing network communication.
`rafthttp: request cluster ID mismatch`	The node with the etcd instance logging `rafthttp: request cluster ID mismatch` is trying to join a cluster that has already been formed with another peer. The node should be removed from the cluster, and re-added.
`rafthttp: failed to find member`	The cluster state (`/var/lib/etcd`) contains wrong information to join the cluster. The node should be removed from the cluster, the state directory should be cleaned and the node should be re-added.

etcd Cluster and Connectivity Checks

The address where etcd is listening depends on the address configuration of the host etcd is running on. If an internal address is configured for the host etcd is running on, the endpoint for etcdctl needs to be specified explicitly. If any of the commands respond with Error: context deadline exceeded, the etcd instance is unhealthy (either quorum is lost or the instance is not correctly joined in the cluster)

Check etcd Members on all Nodes

Output should contain all the nodes with the etcd role and the output should be identical on all nodes.

RKE2: Run the command inside the etcd container.

crictl exec $etcdcontainer etcdctl member list \
  --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt \
  --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key \
  --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl member list \
  --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt \
  --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key \
  --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Example output:

1c424074df86e854, started, cluster-node1-f289ac71, https://IP:2380, https://IP:2379, false
45c68c44c5a792ff, started, cluster-node2-67e3cf6f, https://IP:2380, https://IP:2379, false
7c584f77c5180258, started, cluster-node3-e976bc00, https://IP:2380, https://IP:2379, false

Check Endpoint Status

The values for RAFT TERM should be equal and RAFT INDEX should be not be too far apart from each other.

RKE2:

crictl exec $etcdcontainer etcdctl endpoint status --write-out table --endpoints=$(crictl exec $etcdcontainer etcdctl member list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | cut -d, -f5 | sed -e 's/ //g' | paste -sd ',') --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl endpoint status --write-out table --endpoints=$(etcdctl member list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | cut -d, -f5 | sed -e 's/ //g' | paste -sd ',') --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Example output:

+-----------------+------------------+---------+---------+-----------+-----------+------------+
| ENDPOINT        |        ID        | VERSION | DB SIZE | IS LEADER | RAFT TERM | RAFT INDEX |
+-----------------+------------------+---------+---------+-----------+-----------+------------+
| https://IP:2379 | 333ef673fc4add56 |  3.6.7  |   24 MB |     false |        72 |      66887 |
| https://IP:2379 | 5feed52d940ce4cf |  3.6.7  |   24 MB |      true |        72 |      66887 |
| https://IP:2379 | db6b3bdb559a848d |  3.6.7  |   25 MB |     false |        72 |      66887 |
+-----------------+------------------+---------+---------+-----------+-----------+------------+

Check Endpoint Health

RKE2:

crictl exec $etcdcontainer etcdctl endpoint health --endpoints=$(crictl exec $etcdcontainer etcdctl member list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | cut -d, -f5 | sed -e 's/ //g' | paste -sd ',') --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl endpoint health --endpoints=$(etcdctl member list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | cut -d, -f5 | sed -e 's/ //g' | paste -sd ',') --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Example output:

https://IP:2379 is healthy: successfully committed proposal: took = 2.113189ms
https://IP:2379 is healthy: successfully committed proposal: took = 2.649963ms
https://IP:2379 is healthy: successfully committed proposal: took = 2.451201ms

Check Connectivity on etcd Ports

In modern versions of Kubernetes, the etcd database (versions 3.5 and newer) introduced significant architectural changes regarding network traffic handling. Previously, etcd permitted standard HTTP REST requests on its primary client port (2379). However, to enhance performance and security, etcd 3.5+ strictly enforces the gRPC protocol on this port.
If you attempt to use standard HTTP tools like curl to test connectivity on port 2379, the etcd server will automatically terminate the connection or return an error. This behavior often leads administrators to misinterpret the result as a closed port or a node failure.

Since standard HTTP clients can no longer probe the primary etcd ports, the transport layer must be utilized for network troubleshooting. Using openssl s_client instead of curl bypasses the gRPC application requirement, allowing the raw TCP and TLS handshake to be tested directly.

These script isolate the network and security infrastructure from the database application. A successful Verify return code: 0 (ok) explicitly confirms four critical infrastructure components:

Network Path: Routing is functional, and firewalls permit traffic on TCP port 2379 or 2380.
Process Availability: The etcd service is running and actively listening on the designated port.
Certificate Validity: The TLS certificates are active, correctly formatted, and have not expired.
Mutual Authentication (mTLS): The node successfully authenticates against the cluster's specific Certificate Authority (CA).

How these tests differ from the etcdctl endpoint health test:

If etcdctl endpoint health test is failing, run these Connectivity Ports test scripts. If the scripts succeed, your network and certificates are intact, and the issue is likely confined to the etcd database itself. If these scripts fail, the issue is related to a firewall/network restriction, or certificate expiration.

Port TCP/2379

RKE2:

for endpoint in $(crictl exec $etcdcontainer etcdctl member list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | cut -d, -f5); do
  echo "Validating connection to ${endpoint} (Client)";
  echo | openssl s_client -connect ${endpoint#https://} \
    -CAfile /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt \
    -cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt \
    -key /var/lib/rancher/rke2/server/tls/etcd/server-client.key 2>/dev/null | grep -E 'Verify return code' || echo "Connection Failed/Timeout"
done

K3s:

for endpoint in $(etcdctl member list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | cut -d, -f5); do
  echo "Validating connection to ${endpoint} (Client)";
  echo | openssl s_client -connect ${endpoint#https://} \
    -CAfile /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt \
    -cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt \
    -key /var/lib/rancher/k3s/server/tls/etcd/server-client.key 2>/dev/null | grep -E 'Verify return code' || echo "Connection Failed/Timeout"
done

Example output:

Validating connection to https://IP:2379/health (Client)
Verify return code: 0 (ok)
Validating connection to https://IP:2379/health (Client)
Verify return code: 0 (ok)
Validating connection to https://IP:2379/health (Client)
Verify return code: 0 (ok)

Port TCP/2380

RKE2:

for endpoint in $(crictl exec $etcdcontainer etcdctl member list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | cut -d, -f4); do
  echo "Validating connection to ${endpoint} (Peer)";
  echo | openssl s_client -connect ${endpoint#https://} \
    -CAfile /var/lib/rancher/rke2/server/tls/etcd/peer-ca.crt \
    -cert /var/lib/rancher/rke2/server/tls/etcd/peer-server-client.crt \
    -key /var/lib/rancher/rke2/server/tls/etcd/peer-server-client.key 2>/dev/null | grep -E 'Verify return code' || echo "Connection Failed/Timeout"
done

K3s:

for endpoint in $(etcdctl member list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | cut -d, -f4); do
  echo "Validating connection to ${endpoint} (Peer)";
  echo | openssl s_client -connect ${endpoint#https://} \
    -CAfile /var/lib/rancher/k3s/server/tls/etcd/peer-ca.crt \
    -cert /var/lib/rancher/k3s/server/tls/etcd/peer-server-client.crt \
    -key /var/lib/rancher/k3s/server/tls/etcd/peer-server-client.key 2>/dev/null | grep -E 'Verify return code' || echo "Connection Failed/Timeout"
done

Example output:

Validating connection to https://IP:2380/version (Peer)
Verify return code: 0 (ok)
Validating connection to https://IP:2380/version (Peer)
Verify return code: 0 (ok)
Validating connection to https://IP:2380/version (Peer)
Verify return code: 0 (ok)

etcd Alarms

etcd will trigger alarms, for instance when it runs out of space.

RKE2:

crictl exec $etcdcontainer etcdctl alarm list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl alarm list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Example output when NOSPACE alarm is triggered:

memberID:x alarm:NOSPACE
memberID:x alarm:NOSPACE
memberID:x alarm:NOSPACE

etcd Space Errors

Related error messages are etcdserver: mvcc: database space exceeded or applying raft message exceeded backend quota. Alarm NOSPACE will be triggered.

Resolutions:

Compact the Keyspace
Defrag All etcd Members
Check Endpoint Status
Disarm Alarm

Compact the Keyspace

RKE2:

rev=$(crictl exec $etcdcontainer etcdctl endpoint status --write-out json --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | egrep -o '"revision":[0-9]*' | egrep -o '[0-9]*' | head -1)
crictl exec $etcdcontainer etcdctl compact "$rev" --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

rev=$(etcdctl endpoint status --write-out json --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | egrep -o '"revision":[0-9]*' | egrep -o '[0-9]*' | head -1)
etcdctl compact "$rev" --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Example output:

compacted revision xxx

Defrag All etcd Members

RKE2:

crictl exec $etcdcontainer etcdctl defrag --endpoints=$(crictl exec $etcdcontainer etcdctl member list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | cut -d, -f5 | sed -e 's/ //g' | paste -sd ',') --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl defrag --endpoints=$(etcdctl member list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | cut -d, -f5 | sed -e 's/ //g' | paste -sd ',') --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Example output:

Finished defragmenting etcd member[https://IP:2379]. took xx.xxxxxxms
Finished defragmenting etcd member[https://IP:2379]. took xx.xxxxxxms
Finished defragmenting etcd member[https://IP:2379]. took xx.xxxxxxms

Disarm Alarm

After verifying that the DB size went down after compaction and defragmenting, the alarm needs to be disarmed for etcd to allow writes again.

RKE2:

crictl exec $etcdcontainer etcdctl alarm list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt
crictl exec $etcdcontainer etcdctl alarm disarm --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt
crictl exec $etcdcontainer etcdctl alarm list --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl alarm list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt
etcdctl alarm disarm --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt
etcdctl alarm list --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

Configure Log Level

:::note

You can no longer dynamically change the log level in etcd v3.5 or later.

:::

etcd v3.5 And Later

To configure the log level for etcd, edit the cluster configuration YAML:

services:
  etcd:
    extra_args:
      log-level: "debug"

After modifying the configuration, restart the service (systemctl restart rke2-server or systemctl restart k3s) if you are configuring a stand-alone cluster.

etcd Content

If you want to investigate the contents of your etcd, you can either watch streaming events or you can query etcd directly, see below for examples.

Watch Streaming Events

RKE2:

crictl exec $etcdcontainer etcdctl watch --prefix /registry --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl watch --prefix /registry --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

If you only want to see the affected keys (and not the binary data), you can append | grep -a ^/registry to the command to filter for keys only.

Query etcd Directly

RKE2:

crictl exec $etcdcontainer etcdctl get /registry --prefix=true --keys-only --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt

K3s:

etcdctl get /registry --prefix=true --keys-only --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt

You can process the data to get a summary of count per key, using the command below:

RKE2:

crictl exec $etcdcontainer etcdctl get /registry --prefix=true --keys-only --cert /var/lib/rancher/rke2/server/tls/etcd/server-client.crt --key /var/lib/rancher/rke2/server/tls/etcd/server-client.key --cacert /var/lib/rancher/rke2/server/tls/etcd/server-ca.crt | grep -v ^$ | awk -F'/' '{ if ($3 ~ /cattle.io/) {h[$3"/"$4]++} else { h[$3]++ }} END { for(k in h) print h[k], k }' | sort -nr

K3s:

etcdctl get /registry --prefix=true --keys-only --cert /var/lib/rancher/k3s/server/tls/etcd/server-client.crt --key /var/lib/rancher/k3s/server/tls/etcd/server-client.key --cacert /var/lib/rancher/k3s/server/tls/etcd/server-ca.crt | grep -v ^$ | awk -F'/' '{ if ($3 ~ /cattle.io/) {h[$3"/"$4]++} else { h[$3]++ }} END { for(k in h) print h[k], k }' | sort -nr

Replacing Unhealthy etcd Nodes

When a node in your etcd cluster becomes unhealthy, the recommended approach is to fix or remove the failed or unhealthy node before adding a new etcd node to the cluster.

21 KiB Raw Blame History

Prerequisites

RKE2

K3s

⚠️ Warning

Checking if the etcd Container is Running

etcd Logging

etcd Cluster and Connectivity Checks

Check etcd Members on all Nodes

Check Endpoint Status

Check Endpoint Health

Check Connectivity on etcd Ports

Port TCP/2379

Port TCP/2380

etcd Alarms

etcd Space Errors

Compact the Keyspace

Defrag All etcd Members

Disarm Alarm

Configure Log Level

etcd v3.5 And Later

etcd Content

Watch Streaming Events

Query etcd Directly

Replacing Unhealthy etcd Nodes

21 KiB

Raw Blame History