---
title: Generate Certificates Manually
content_type: task
weight: 30
---

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When using client certificate authentication, you can generate certificates
manually through [`easyrsa`](https://github.com/OpenVPN/easy-rsa), [`openssl`](https://github.com/openssl/openssl) or [`cfssl`](https://github.com/cloudflare/cfssl).

<!-- body -->

### easyrsa

**easyrsa** can manually generate certificates for your cluster.

1. Download, unpack, and initialize the patched version of `easyrsa3`.

   ```shell
   curl -LO https://dl.k8s.io/easy-rsa/easy-rsa.tar.gz
   tar xzf easy-rsa.tar.gz
   cd easy-rsa-master/easyrsa3
   ./easyrsa init-pki
   ```
1. Generate a new certificate authority (CA). `--batch` sets automatic mode;
   `--req-cn` specifies the Common Name (CN) for the CA's new root certificate.

   ```shell
   ./easyrsa --batch "--req-cn=${MASTER_IP}@`date +%s`" build-ca nopass
   ```

1. Generate server certificate and key.

   The argument `--subject-alt-name` sets the possible IPs and DNS names the API server will
   be accessed with. The `MASTER_CLUSTER_IP` is usually the first IP from the service CIDR
   that is specified as the `--service-cluster-ip-range` argument for both the API server and
   the controller manager component. The argument `--days` is used to set the number of days
   after which the certificate expires.
   The sample below also assumes that you are using `cluster.local` as the default
   DNS domain name.

   ```shell
   ./easyrsa --subject-alt-name="IP:${MASTER_IP},"\
   "IP:${MASTER_CLUSTER_IP},"\
   "DNS:kubernetes,"\
   "DNS:kubernetes.default,"\
   "DNS:kubernetes.default.svc,"\
   "DNS:kubernetes.default.svc.cluster,"\
   "DNS:kubernetes.default.svc.cluster.local" \
   --days=10000 \
   build-server-full server nopass
   ```

1. Copy `pki/ca.crt`, `pki/issued/server.crt`, and `pki/private/server.key` to your directory.

1. Fill in and add the following parameters into the API server start parameters:

   ```shell
   --client-ca-file=/yourdirectory/ca.crt
   --tls-cert-file=/yourdirectory/server.crt
   --tls-private-key-file=/yourdirectory/server.key
   ```

### openssl

**openssl** can manually generate certificates for your cluster.

1. Generate a ca.key with 2048bit:

   ```shell
   openssl genrsa -out ca.key 2048
   ```

1. According to the ca.key generate a ca.crt (use `-days` to set the certificate effective time):

   ```shell
   openssl req -x509 -new -nodes -key ca.key -subj "/CN=${MASTER_IP}" -days 10000 -out ca.crt
   ```

1. Generate a server.key with 2048bit:

   ```shell
   openssl genrsa -out server.key 2048
   ```

1. Create a config file for generating a Certificate Signing Request (CSR).

   Be sure to substitute the values marked with angle brackets (e.g. `<MASTER_IP>`)
   with real values before saving this to a file (e.g. `csr.conf`).
   Note that the value for `MASTER_CLUSTER_IP` is the service cluster IP for the
   API server as described in previous subsection.
   The sample below also assumes that you are using `cluster.local` as the default
   DNS domain name.

   ```ini
   [ req ]
   default_bits = 2048
   prompt = no
   default_md = sha256
   req_extensions = req_ext
   distinguished_name = dn

   [ dn ]
   C = <country>
   ST = <state>
   L = <city>
   O = <organization>
   OU = <organization unit>
   CN = <MASTER_IP>

   [ req_ext ]
   subjectAltName = @alt_names

   [ alt_names ]
   DNS.1 = kubernetes
   DNS.2 = kubernetes.default
   DNS.3 = kubernetes.default.svc
   DNS.4 = kubernetes.default.svc.cluster
   DNS.5 = kubernetes.default.svc.cluster.local
   IP.1 = <MASTER_IP>
   IP.2 = <MASTER_CLUSTER_IP>

   [ v3_ext ]
   authorityKeyIdentifier=keyid,issuer:always
   basicConstraints=CA:FALSE
   keyUsage=keyEncipherment,dataEncipherment
   extendedKeyUsage=serverAuth,clientAuth
   subjectAltName=@alt_names
   ```

1. Generate the certificate signing request based on the config file:

   ```shell
   openssl req -new -key server.key -out server.csr -config csr.conf