What and where is the default kubeadm config file? - kubernetes

Question

Using kubeadm init initializes the control plane with default configuration options.
Is there a way to see what default values/configuration it will use for the control plane, how can I view that configuration file, and where is it stored?

Answer 1

Found the command: ( just in case someone needs it)
C02W84XMHTD5:~ iahmad$ kubectl get configMap kubeadm-config -o yaml --namespace=kube-system
apiVersion: v1
data:
MasterConfiguration: |
api:
advertiseAddress: 192.168.64.4
bindPort: 8443
controlPlaneEndpoint: localhost
apiServerExtraArgs:
admission-control: Initializers,NamespaceLifecycle,LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,NodeRestriction,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,ResourceQuota
auditPolicy:
logDir: /var/log/kubernetes/audit
logMaxAge: 2
path: ""
authorizationModes:
- Node
- RBAC
certificatesDir: /var/lib/minikube/certs/
cloudProvider: ""
criSocket: /var/run/dockershim.sock
etcd:
caFile: ""
certFile: ""
dataDir: /data/minikube
endpoints: null
image: ""
keyFile: ""
imageRepository: k8s.gcr.io
kubeProxy:
config:
bindAddress: 0.0.0.0
clientConnection:
acceptContentTypes: ""
burst: 10
contentType: application/vnd.kubernetes.protobuf
kubeconfig: /var/lib/kube-proxy/kubeconfig.conf
qps: 5
clusterCIDR: ""
configSyncPeriod: 15m0s
conntrack:
max: null
maxPerCore: 32768
min: 131072
tcpCloseWaitTimeout: 1h0m0s
tcpEstablishedTimeout: 24h0m0s
enableProfiling: false
healthzBindAddress: 0.0.0.0:10256
hostnameOverride: ""
iptables:
masqueradeAll: false
masqueradeBit: 14
minSyncPeriod: 0s
syncPeriod: 30s
ipvs:
minSyncPeriod: 0s
scheduler: ""
syncPeriod: 30s
metricsBindAddress: 127.0.0.1:10249
mode: ""
nodePortAddresses: null
oomScoreAdj: -999
portRange: ""
resourceContainer: /kube-proxy
udpIdleTimeout: 250ms
kubeletConfiguration: {}
kubernetesVersion: v1.10.0
networking:
dnsDomain: cluster.local
podSubnet: ""
serviceSubnet: 10.96.0.0/12
noTaintMaster: true
nodeName: minikube
privilegedPods: false
token: ""
tokenGroups:
- system:bootstrappers:kubeadm:default-node-token
tokenTTL: 24h0m0s
tokenUsages:
- signing
- authentication
unifiedControlPlaneImage: ""

Answer 2

kubeadm config print init-defaults (cf. join-defaults) will show the defaults:
$ kubeadm config print init-defaults
apiVersion: kubeadm.k8s.io/v1beta2
bootstrapTokens:
- groups:
- system:bootstrappers:kubeadm:default-node-token
token: abcdef.0123456789abcdef
ttl: 24h0m0s
usages:
- signing
- authentication
kind: InitConfiguration
localAPIEndpoint:
advertiseAddress: 1.2.3.4
bindPort: 6443
nodeRegistration:
criSocket: /var/run/dockershim.sock
name: k1.london.vultr
taints:
- effect: NoSchedule
key: node-role.kubernetes.io/master
---
apiServer:
timeoutForControlPlane: 4m0s
apiVersion: kubeadm.k8s.io/v1beta2
certificatesDir: /etc/kubernetes/pki
clusterName: kubernetes
controllerManager: {}
dns:
type: CoreDNS
etcd:
local:
dataDir: /var/lib/etcd
imageRepository: k8s.gcr.io
kind: ClusterConfiguration
kubernetesVersion: v1.16.0
networking:
dnsDomain: cluster.local
serviceSubnet: 10.96.0.0/12
scheduler: {}
(kubeadm v1.16.0)
As far as I can tell these are built-in defaults, and there is no overridable defaults file, i.e. to supply a different config file it is necessary to pass --config=<file>.