If you run docker network ls and do not see a network that you’re looking for, what is the most likely culprit?culprit?
- That node is not a worker node.
- That node is not a manager node.
- You’re not authorized to see the network.
- That node doesn’t have a container running that uses that network. (Ans)
What does –update-parallelism control?
- The time between updating tasks
- The number of tasks updated at the same time (Ans)
- What to do when an update fails
- Whether or not to update all tasks at once, or one at a time
Which published port mode would you use to load balance requests across all containers for a service?
- Host
- None
- Ingress
- Bridge (Ans)
- LoadBalanced
If you only have a replicated service, what will happen when you add a new node to the cluster?
- The pending task for the service will be assigned to the new node and a container will be started.
- The existing containers for the service will be rebalanced so that a fair share are placed onto the new node.
- Nothing will run on the new node unless you change the service. (Ans)
- A new task will be allocated to the new node for the global service.
If you want multiple containers for an application, what command is easiest to use to go from a service with one task replicas to two?
- docker clone …
- docker service rm; docker service create –replicas 2 …
- docker service scale …
- docker service update –replicas 2 … (Ans)
- docker run …
On a swarm, if a container dies that’s part of a service, and a new container is created, what concept explains this?
- High Availability
- Desired State Reconciliation (Ans)
- Scheduling
- Service Scaling
What does the “*” mean in the output of docker node ls?
- The nearest manager
- The leader
- A worker node
- The node you’re connected to (Ans)
Joining a node as a manager by default that node will perform __ role(s).
- Manager only
- Leader only
- Manager and Worker (Ans)
- Replica only
- Slave and Replica
Which of the following would you use to decrease the time between health checks?
- retries
- CMD
- timeout
- interval (Ans)
Assuming you have a stack called APIS, what is the equivalent of docker service ls for stacks?
- docker stack deploy
- docker stack services APIS (Ans)
- docker stack ps APIS
- docker stack ls
What happens to containers on a node that you drain?
- They’re shut down until you make the node active again.
- They keep running, just no new work is allowed to be put onto the node.
- They’re snapshotted and migrated to other nodes.
- They’re terminated and migrated as new containers on other nodes. (Ans)
Assuming you have a service named web, what will the dns query tasks.web return?
- The Swarm Load Balancer
- Individual container IPs for the web service (Ans)
- The web service’s Virtual IP
What does –update-delay control?
- What to do when an update fails
- The number of tasks updated at the same time
- The time between updating tasks (Ans)
- Whether or not to update all tasks at once, or one at a time
What command do you use to create containers on a swarm?
- docker service create (Ans)
- docker swarm run
- docker run
- docker-compose up
Which of the following has a one-to-one relationship with a container?
- Task (Ans)
- Service
- Image
- Swarm
What can you put in front of a swarm so that end users don’t have to pick a node, nor deal with node failures, to access a service with a published port?
- Round Robin DNS to all nodes
- Load Balancer to all nodes (Ans)
- Single DNS entry to one node
When no nodes in the cluster fulfill the constraints of a service, what is the status of the service?
- Failed
- Running
- Pending (Ans)
- Started
What does “starting” mean in terms of health checks?
- The health check has not yet run for a new container. (Ans)
- This shows each time the health check runs to indicate that it is starting.
- The health checking service is starting up and is not ready to run health checks.
What happens when Docker Swarm Mode detects an unhealthy container?
- Restarts the container
- Shuts the corresponding task down and starts a new one (Ans)
- Nothing, health checks are not integrated into Swarm Mode.
- Sends an email to the system operator
Which of the following would you use to avoid recreating a task on a recoverable application failure?
- retries (Ans)
- timeout
- interval
- CMD
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