How to fix Error response from daemon: This node is not a swarm manager in Docker

First, check if your Docker node is part of a swarm and what its role is:

docker info --format '{{.Swarm.LocalNodeState}}'

Possible outputs:
- inactive - Not part of any swarm
- active - Part of a swarm (check role next)
- pending - In process of joining a swarm
- locked - Swarm is locked, needs to be unlocked

If active, check if you're a manager:

docker info --format '{{.Swarm.ControlAvailable}}'

Returns true for managers, false for workers.

If docker info shows Swarm: inactive, initialize a new swarm:

docker swarm init

This creates a new single-node swarm with your current node as the manager.

If you have multiple network interfaces, specify which IP to advertise:

docker swarm init --advertise-addr <YOUR_IP>

After initialization, your node becomes both a manager and a worker by default.

If a swarm already exists and you need to join it as a manager, get the join token from an existing manager:

On an existing manager node:

docker swarm join-token manager

This outputs a command like:

docker swarm join --token SWMTKN-1-xxx <MANAGER_IP>:2377

On the node you want to add:

Run the command output from above. Your node will join as a manager.

If you're on a manager node and need to promote a worker:

# List all nodes
docker node ls

# Promote a worker to manager
docker node promote <NODE_ID_OR_HOSTNAME>

You can also demote a manager to worker if needed:

docker node demote <NODE_ID_OR_HOSTNAME>

Note: Always maintain an odd number of managers for proper quorum.

If swarm stopped working after system sleep or restart on Docker Desktop:

Option 1: Restart Docker Desktop
- Right-click the Docker icon in the system tray
- Select "Restart"

Option 2: Leave and reinitialize swarm

docker swarm leave --force
docker swarm init

Option 3: Reset Docker Desktop to factory defaults
- Open Docker Desktop Settings
- Go to "Troubleshoot" or "Reset"
- Click "Reset to factory defaults" (this removes all containers, images, and volumes)

Confirm swarm is working:

# Check swarm status
docker info | grep -A 5 "Swarm"

# List nodes (should work without error)
docker node ls

# Test service creation
docker service create --name test-nginx --replicas 1 nginx
docker service ls
docker service rm test-nginx

If all commands succeed, swarm mode is working correctly.