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kubeadm: improvements to the cert management documentation (#18397)

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- move the sections about custom certificates and external CA
to the kubeadm-certs page
- minor cleanups to the kubeadm-certs page, including updated output
for the check-expiration command
- link the implementation details page to the new locations
for custom certs and external CA
This commit is contained in:
Lubomir I. Ivanov
2020-01-03 19:45:42 +02:00
committed by Kubernetes Prow Robot
parent 70936d4dbd
commit f510b223e9
3 changed files with 55 additions and 41 deletions
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content/en/docs/reference/setup-tools/kubeadm/implementation-details.md
+3 -3
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@@ -150,12 +150,12 @@ Certificates are stored by default in `/etc/kubernetes/pki`, but this directory
1. If a given certificate and private key pair both exist, and its content is evaluated compliant with the above specs, the existing files will
be used and the generation phase for the given certificate skipped. This means the user can, for example, copy an existing CA to
`/etc/kubernetes/pki/ca.{crt,key}`, and then kubeadm will use those files for signing the rest of the certs.
See also [using custom certificates](/docs/reference/setup-tools/kubeadm/kubeadm-init/#custom-certificates)
See also [using custom certificates](/docs/tasks/administer-cluster/kubeadm/kubeadm-certs#custom-certificates)
2. Only for the CA, it is possible to provide the `ca.crt` file but not the `ca.key` file, if all other certificates and kubeconfig files
already are in place kubeadm recognize this condition and activates the ExternalCA , which also implies the `csrsigner`controller in
controller-manager won't be started
3. If kubeadm is running in [ExternalCA mode](/docs/reference/setup-tools/kubeadm/kubeadm-init/#external-ca-mode); all the certificates must be provided by the user,
because kubeadm cannot generate them by itself
3. If kubeadm is running in [external CA mode](/docs/tasks/administer-cluster/kubeadm/kubeadm-certs#external-ca-mode);
all the certificates must be provided by the user, because kubeadm cannot generate them by itself
4. In case of kubeadm is executed in the `--dry-run` mode, certificates files are written in a temporary folder
5. Certificate generation can be invoked individually with the [`kubeadm init phase certs all`](/docs/reference/setup-tools/kubeadm/kubeadm-init-phase/#cmd-phase-certs) command
content/en/docs/reference/setup-tools/kubeadm/kubeadm-init.md
+6 -25
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@@ -26,8 +26,7 @@ following steps:
1. Generates a self-signed CA (or using an existing one if provided) to set up
identities for each component in the cluster. If the user has provided their
own CA cert and/or key by dropping it in the cert directory configured via `--cert-dir`
(`/etc/kubernetes/pki` by default) this step is skipped as described in the
[Using custom certificates](#custom-certificates) document.
(`/etc/kubernetes/pki` by default).
The APIServer certs will have additional SAN entries for any `--apiserver-cert-extra-sans` arguments, lowercased if necessary.
1. Writes kubeconfig files in `/etc/kubernetes/` for
@@ -177,30 +176,12 @@ The following command can be used to generate a new key on demand:
kubeadm alpha certs certificate-key
```
### Using custom certificates {#custom-certificates}
### Certificate management with kubeadm
By default, kubeadm generates all the certificates needed for a cluster to run.
You can override this behavior by providing your own certificates.
To do so, you must place them in whatever directory is specified by the
`--cert-dir` flag or `CertificatesDir` configuration file key. By default this
is `/etc/kubernetes/pki`.
If a given certificate and private key pair exists before running `kubeadm init`,
kubeadm will not overwrite them. This means you can, for example, copy an existing
CA into `/etc/kubernetes/pki/ca.crt` and `/etc/kubernetes/pki/ca.key`,
and kubeadm will use this CA for signing the rest of the certificates.
#### External CA mode {#external-ca-mode}
It is also possible to provide just the `ca.crt` file and not the
`ca.key` file (this is only available for the root CA file, not other cert pairs).
If all other certificates and kubeconfig files are in place, kubeadm recognizes
this condition and activates the "External CA" mode. kubeadm will proceed without the
CA key on disk.
Instead, run the controller-manager standalone with `--controllers=csrsigner` and
point to the CA certificate and key.
For detailed information on certificate management with kubeadm see
[Certificate Management with kubeadm](/docs/tasks/administer-cluster/kubeadm/kubeadm-certs/).
The document includes information about using external CA, custom certificates
and certificate renewal.
### Managing the kubeadm drop-in file for the kubelet {#kubelet-drop-in}