06efc07f46
Almost 100% mechanical change, except the fact that import/import.md is moved to import/README.md No content changes. Signed-off-by: Miek Gieben <miek@miek.nl>
261 lines
11 KiB
Groff
261 lines
11 KiB
Groff
.\" generated with Ronn/v0.7.3
|
|
.\" http://github.com/rtomayko/ronn/tree/0.7.3
|
|
.
|
|
.TH "COREDNS\-KUBERNETES" "7" "January 2019" "CoreDNS" "CoreDNS plugins"
|
|
.
|
|
.SH "NAME"
|
|
\fIkubernetes\fR \- enables the reading zone data from a Kubernetes cluster\.
|
|
.
|
|
.SH "DESCRIPTION"
|
|
This plugin implements the Kubernetes DNS\-Based Service Discovery Specification \fIhttps://github\.com/kubernetes/dns/blob/master/docs/specification\.md\fR\.
|
|
.
|
|
.P
|
|
CoreDNS running the kubernetes plugin can be used as a replacement for kube\-dns in a kubernetes cluster\. See the deployment \fIhttps://github\.com/coredns/deployment\fR repository for details on how to deploy CoreDNS in Kubernetes \fIhttps://github\.com/coredns/deployment/tree/master/kubernetes\fR\.
|
|
.
|
|
.P
|
|
stubDomains and upstreamNameservers \fIhttp://blog\.kubernetes\.io/2017/04/configuring\-private\-dns\-zones\-upstream\-nameservers\-kubernetes\.html\fR are implemented via the \fIproxy\fR plugin and kubernetes \fIupstream\fR\. See example below\.
|
|
.
|
|
.P
|
|
This plugin can only be used once per Server Block\.
|
|
.
|
|
.SH "SYNTAX"
|
|
.
|
|
.nf
|
|
|
|
kubernetes [ZONES\.\.\.]
|
|
.
|
|
.fi
|
|
.
|
|
.P
|
|
With only the directive specified, the \fIkubernetes\fR plugin will default to the zone specified in the server\'s block\. It will handle all queries in that zone and connect to Kubernetes in\-cluster\. It will not provide PTR records for services or A records for pods\. If \fBZONES\fR is used it specifies all the zones the plugin should be authoritative for\.
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
kubernetes [ZONES\.\.\.] {
|
|
resyncperiod DURATION
|
|
endpoint URL [URL\.\.\.]
|
|
tls CERT KEY CACERT
|
|
kubeconfig KUBECONFIG CONTEXT
|
|
namespaces NAMESPACE\.\.\.
|
|
labels EXPRESSION
|
|
pods POD\-MODE
|
|
endpoint_pod_names
|
|
upstream [ADDRESS\.\.\.]
|
|
ttl TTL
|
|
noendpoints
|
|
transfer to ADDRESS\.\.\.
|
|
fallthrough [ZONES\.\.\.]
|
|
ignore empty_service
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBresyncperiod\fR specifies the Kubernetes data API \fBDURATION\fR period\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBendpoint\fR specifies the \fBURL\fR for a remote k8s API endpoint\. If omitted, it will connect to k8s in\-cluster using the cluster service account\. Multiple k8s API endpoints could be specified: \fBendpoint http://k8s\-endpoint1:8080 http://k8s\-endpoint2:8080\fR\. CoreDNS will automatically perform a healthcheck and proxy to the healthy k8s API endpoint\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBtls\fR \fBCERT\fR \fBKEY\fR \fBCACERT\fR are the TLS cert, key and the CA cert file names for remote k8s connection\. This option is ignored if connecting in\-cluster (i\.e\. endpoint is not specified)\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBkubeconfig\fR \fBKUBECONFIG\fR \fBCONTEXT\fR authenticates the connection to a remote k8s cluster using a kubeconfig file\. It supports TLS, username and password, or token\-based authentication\. This option is ignored if connecting in\-cluster (i\.e\., the endpoint is not specified)\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBnamespaces\fR \fBNAMESPACE [NAMESPACE\.\.\.]\fR only exposes the k8s namespaces listed\. If this option is omitted all namespaces are exposed
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBlabels\fR \fBEXPRESSION\fR only exposes the records for Kubernetes objects that match this label selector\. The label selector syntax is described in the Kubernetes User Guide \- Labels \fIhttp://kubernetes\.io/docs/user\-guide/labels/\fR\. An example that only exposes objects labeled as "application=nginx" in the "staging" or "qa" environments, would use: \fBlabels environment in (staging, qa),application=nginx\fR\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBpods\fR \fBPOD\-MODE\fR sets the mode for handling IP\-based pod A records, e\.g\. \fB1\-2\-3\-4\.ns\.pod\.cluster\.local\. in A 1\.2\.3\.4\fR\. This option is provided to facilitate use of SSL certs when connecting directly to pods\. Valid values for \fBPOD\-MODE\fR:
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBdisabled\fR: Default\. Do not process pod requests, always returning \fBNXDOMAIN\fR
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBinsecure\fR: Always return an A record with IP from request (without checking k8s)\. This option is vulnerable to abuse if used maliciously in conjunction with wildcard SSL certs\. This option is provided for backward compatibility with kube\-dns\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBverified\fR: Return an A record if there exists a pod in same namespace with matching IP\. This option requires substantially more memory than in insecure mode, since it will maintain a watch on all pods\.
|
|
.
|
|
.IP "" 0
|
|
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBendpoint_pod_names\fR uses the pod name of the pod targeted by the endpoint as the endpoint name in A records, e\.g\., \fBendpoint\-name\.my\-service\.namespace\.svc\.cluster\.local\. in A 1\.2\.3\.4\fR By default, the endpoint\-name name selection is as follows: Use the hostname of the endpoint, or if hostname is not set, use the dashed form of the endpoint IP address (e\.g\., \fB1\-2\-3\-4\.my\-service\.namespace\.svc\.cluster\.local\.\fR) If this directive is included, then name selection for endpoints changes as follows: Use the hostname of the endpoint, or if hostname is not set, use the pod name of the pod targeted by the endpoint\. If there is no pod targeted by the endpoint, use the dashed IP address form\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBupstream\fR [\fBADDRESS\fR\.\.\.] defines the upstream resolvers used for resolving services that point to external hosts (aka External Services, aka CNAMEs)\. If no \fBADDRESS\fR is given, CoreDNS will resolve External Services against itself\. \fBADDRESS\fR can be an IP, an IP:port, or a path to a file structured like resolv\.conf\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBttl\fR allows you to set a custom TTL for responses\. The default (and minimum allowed) is 0 seconds, while the maximum is capped at 3600 seconds\. Setting TTL to 0 will prevent records from being cached\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBnoendpoints\fR will turn off the serving of endpoint records by disabling the watch on endpoints\. All endpoint queries and headless service queries will result in an NXDOMAIN\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBtransfer\fR enables zone transfers\. It may be specified multiples times\. \fBTo\fR signals the direction (only \fBto\fR is allow)\. \fBADDRESS\fR must be denoted in CIDR notation (127\.0\.0\.1/32 etc\.) or just as plain addresses\. The special wildcard \fB*\fR means: the entire internet\. Sending DNS notifies is not supported\. Deprecated \fIhttps://github\.com/kubernetes/dns/blob/master/docs/specification\.md#26\-\-\-deprecated\-records\fR pod records in the subdomain \fBpod\.cluster\.local\fR are not transferred\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBfallthrough\fR \fB[ZONES\.\.\.]\fR If a query for a record in the zones for which the plugin is authoritative results in NXDOMAIN, normally that is what the response will be\. However, if you specify this option, the query will instead be passed on down the plugin chain, which can include another plugin to handle the query\. If \fB[ZONES\.\.\.]\fR is omitted, then fallthrough happens for all zones for which the plugin is authoritative\. If specific zones are listed (for example \fBin\-addr\.arpa\fR and \fBip6\.arpa\fR), then only queries for those zones will be subject to fallthrough\.
|
|
.
|
|
.IP "\(bu" 4
|
|
\fBignore empty_service\fR return NXDOMAIN for services without any ready endpoint addresses (e\.g\., ready pods)\. This allows the querying pod to continue searching for the service in the search path\. The search path could, for example, include another Kubernetes cluster\.
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.SH "HEALTH"
|
|
This plugin implements dynamic health checking\. Currently this is limited to reporting healthy when the API has synced\.
|
|
.
|
|
.SH "WATCH"
|
|
This plugin implements watch\. A client that connects to CoreDNS using \fBcoredns/client\fR can be notified of changes to A, AAAA, and SRV records for Kubernetes services and endpoints\.
|
|
.
|
|
.SH "EXAMPLES"
|
|
Handle all queries in the \fBcluster\.local\fR zone\. Connect to Kubernetes in\-cluster\. Also handle all \fBin\-addr\.arpa\fR \fBPTR\fR requests for \fB10\.0\.0\.0/17\fR \. Verify the existence of pods when answering pod requests\. Resolve upstream records against \fB10\.102\.3\.10\fR\. Note we show the entire server block here:
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
10\.0\.0\.0/17 cluster\.local {
|
|
kubernetes {
|
|
pods verified
|
|
upstream 10\.102\.3\.10:53
|
|
}
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.P
|
|
Or you can selectively expose some namespaces:
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
kubernetes cluster\.local {
|
|
namespaces test staging
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.P
|
|
Connect to Kubernetes with CoreDNS running outside the cluster:
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
kubernetes cluster\.local {
|
|
endpoint https://k8s\-endpoint:8443
|
|
tls cert key cacert
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.SH "STUBDOMAINS AND UPSTREAMNAMESERVERS"
|
|
Here we use the \fIproxy\fR plugin to implement a stubDomain that forwards \fBexample\.local\fR to the nameserver \fB10\.100\.0\.10:53\fR\. The \fIupstream\fR option in the \fIkubernetes\fR plugin means that ExternalName services (CNAMEs) will be resolved using the respective proxy\. Also configured is an upstreamNameserver \fB8\.8\.8\.8:53\fR that will be used for resolving names that do not fall in \fBcluster\.local\fR or \fBexample\.local\fR\.
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
\&\.:53 {
|
|
kubernetes cluster\.local {
|
|
upstream
|
|
}
|
|
proxy example\.local 10\.100\.0\.10:53
|
|
proxy \. 8\.8\.8\.8:53
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.P
|
|
The configuration above represents the following Kube\-DNS stubDomains and upstreamNameservers configuration\.
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
stubDomains: |
|
|
{“example\.local”: [“10\.100\.0\.10:53”]}
|
|
upstreamNameservers: |
|
|
[“8\.8\.8\.8:53”]
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.SH "AUTOPATH"
|
|
The \fIkubernetes\fR plugin can be used in conjunction with the \fIautopath\fR plugin\. Using this feature enables server\-side domain search path completion in Kubernetes clusters\. Note: \fBpods\fR must be set to \fBverified\fR for this to function properly\.
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
cluster\.local {
|
|
autopath @kubernetes
|
|
kubernetes {
|
|
pods verified
|
|
}
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.SH "FEDERATION"
|
|
The \fIkubernetes\fR plugin can be used in conjunction with the \fIfederation\fR plugin\. Using this feature enables serving federated domains from the Kubernetes clusters\.
|
|
.
|
|
.IP "" 4
|
|
.
|
|
.nf
|
|
|
|
cluster\.local {
|
|
federation {
|
|
prod prod\.example\.org
|
|
staging staging\.example\.org
|
|
}
|
|
kubernetes
|
|
}
|
|
.
|
|
.fi
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.SH "WILDCARDS"
|
|
Some query labels accept a wildcard value to match any value\. If a label is a valid wildcard (*, or the word "any"), then that label will match all values\. The labels that accept wildcards are:
|
|
.
|
|
.IP "\(bu" 4
|
|
\fIendpoint\fR in an \fBA\fR record request: \fIendpoint\fR\.service\.namespace\.svc\.zone, e\.g\., \fB*\.nginx\.ns\.svc\.cluster\.local\fR
|
|
.
|
|
.IP "\(bu" 4
|
|
\fIservice\fR in an \fBA\fR record request: \fIservice\fR\.namespace\.svc\.zone, e\.g\., \fB*\.ns\.svc\.cluster\.local\fR
|
|
.
|
|
.IP "\(bu" 4
|
|
\fInamespace\fR in an \fBA\fR record request: service\.\fInamespace\fR\.svc\.zone, e\.g\., \fBnginx\.*\.svc\.cluster\.local\fR
|
|
.
|
|
.IP "\(bu" 4
|
|
\fIport and/or protocol\fR in an \fBSRV\fR request: \fBport_\.\fRprotocol_\.service\.namespace\.svc\.zone\., e\.g\., \fB_http\.*\.service\.ns\.svc\.cluster\.local\fR
|
|
.
|
|
.IP "\(bu" 4
|
|
multiple wild cards are allowed in a single query, e\.g\., \fBA\fR Request \fB*\.*\.svc\.zone\.\fR or \fBSRV\fR request \fB*\.*\.*\.*\.svc\.zone\.\fR
|
|
.
|
|
.IP "" 0
|
|
.
|
|
.P
|
|
For example, wildcards can be used to resolve all Endpoints for a Service as \fBA\fR records\. e\.g\.: \fB*\.service\.ns\.svc\.myzone\.local\fR will return the Endpoint IPs in the Service \fBservice\fR in namespace \fBdefault\fR: \fB*\.service\.default\.svc\.cluster\.local\. 5 IN A 192\.168\.10\.10 *\.service\.default\.svc\.cluster\.local\. 5 IN A 192\.168\.25\.15\fR This response can be randomized using the \fBloadbalance\fR plugin
|