Commands CheatSheet

Nano

Ctrl + G: Display Nano's help menu.
Ctrl + K: Cut the current line.
Ctrl + U: Paste the cut text.
Ctrl + C: Display current line and column number.
Ctrl + P: Move cursor to the previous line.
Ctrl + N: Move cursor to the next line.
Ctrl + A: Move cursor to the beginning of the current line.
Ctrl + E: Move cursor to the end of the current line.
Ctrl + \: Move cursor to a specific line number.
Ctrl + W: Search for text.
Alt + W: Repeat search in the opposite direction.
Ctrl + \: Replace text.

UNIX

whoami: Get current user

Kubernetes

Command and Args

command: Setting the Primary Command

• Think of command as the heart of the action, defining the main command to be run within a container.
• Specify it as an array of strings, with each element representing a part of the command.

command: ["echo", "Hello from the container!"]

args: Providing Additional Arguments

• Need to pass extra information to the command? That’s where args come in.

args: ["This message is brought to you by args."]

Security Contexts

Can be configured at the POD level or the CONTAINER level.

• For the POD

...
kind: Pod
...
spec:
    securityContext:
        runAsUser: 1000

• For the CONTAINER. Capabilities are only supported at the container level.

...
kind: Pod
...
spec:
    containers:
        securityContext:
            runAsUser: 1000
            capabilities: 
                add: ["MAC_ADMIN"]

ServiceAccounts

User account is used by humans, service account is used by applications. SA creates a secret with the token that you have to use from the applications in the header "Autorization: Bearer token"

• kubectl commands

k create serviceaccount name
k describe serviceaccount name #to get the related secret name with the token
k create token sa-name # From 1.24 the token is not auto-generated and now is time bound

Resource Request

• Memory: M/G/K/Gi/Mi/Ki
• CPU: 1/100m

...
kind: Pod
...
spec:
  containers:
  - name:
    resources:
      requests:
        memory: "4Gi"
        cpu: 2
      limits:
        memory:
        cpu:

Taints and Tolerations

Nodes have taints and Pods have tolerations to certain taints. If both match, the scheduler place the pod in the node.

kubectl describe node node-name | grep Taint
kubectl taint nodes node-name key=value:taint-effect
# tain-effect can be NoSchedule | PreferNoSchedule | NoExecute

...
kind: Pod
...
spec:
  tolerations:
  - key: "key"
    operator: "equal"
    value: "value"
    effect: "taint-effect"

Docker

Users

• When running the container

docker run --user=1000 ubuntu sleep 3600
docker run --cap-add MAC_ADMIN
docker run --cap-remove KILL

• Or from the Dockerfile

FROM ubuntu
USER 1000