20191023更新：最新版cloudkey系统keytool软连接到了错误位置

/usr/lib/jvm/java-8-openjdk-armhf/jre/bin/keytool -importkeystore -srckeystore unifi.p12 -srcstoretype PKCS12 -srcstorepass aircontrolenterprise -destkeystore unifi.keystore.jks -storepass aircontrolenterprise

此外新版开机证书检测脚本把cert.tar的目录改到了/root/etc/ssl/private，需要注意。更正打包命令，删除cloudkey.crt cloudkey.key unifi.keystore.jks的路径。

unifi的cloud key的web页面默认使用的是自签名的证书，打开时浏览器会提示不信任的页面，从阿里云或者其他地方免费获取证书后替换就能显示小绿锁了。想着替换一个证书而已，没想到这中间还有坑。
首先简单介绍一下cloud key的web架构
首先是80端口，请求http后会返回301跳转到https，然后打开入口页面，一个是unifi controller，一个是cloud key管理
80端口和443端口是nginx监听的，cloud key 管理页面是443端口，但是unifi controller使用的是8443端口，这个是java的
检查nginx配置发现ssl证书在/etc/ssl/private目录下，有cloudkey.crt和cloudkey.key，nginx证书替换好办，直接把新申请的域名证书内容覆盖cloudkey.crt和cloudkey.key内容即可。
麻烦的是java使用的证书，在网上找到办法，需要根据cloudkey.crt和cloudkey.key生产p12格式证书，在用工具生成Java用的证书unifi.keystore.jks，方法如下

cd /etc/ssl/private
openssl pkcs12 -export -in cloudkey.crt -inkey cloudkey.key -out unifi.p12 -name unifi -password pass:aircontrolenterprise
keytool -importkeystore -srckeystore unifi.p12 -srcstoretype PKCS12 -srcstorepass aircontrolenterprise -destkeystore unifi.keystore.jks -storepass aircontrolenterprise
service nginx restart
service unifi restart

现在使用域名打开unifi controller页面，小绿锁出现了。
然后就遇到坑了，重启发现证书又变成了自签名，这就尴尬了，重启不能保存这则么能行。google后有说cloud key重启会重置文件系统的，但是查看df -h，和经过测试，发现并不会重置，那就是有开机脚本操作了。再搜索，ubnt的英文论坛里说/usr/share/initramfs-tools/scripts/ubnt-bottom/configure-sslcert这个脚本每次开机执行，检查/etc/ssl/private/cert.tar这个压缩包里的证书是否和/etc/ssl/private里的一致。分析脚本发现，只要这个tar包只要是非0字节就会解压到临时目录，对比/etc/ssl/private里证书，如果不一致则情况重新生成，并更新cert.tar。
到此，只要保持cert.tar里面到三个文件和外面到一致就可以了。注意，打包时cloudkey.crt cloudkey.key unifi.keystore.jks三个文件不要带路径。

cd /etc/ssl/private && tar cvf /root/etc/ssl/private/cert.tar cloudkey.crt cloudkey.key unifi.keystore.jks

重启，小绿锁还在。

转一个脚本

#!/usr/bin/env bash

###################################################
# Instructions to replace self-signed certificate #
###################################################
# 1. Save this script file to your cloud key
# 2. Use chmod to make this script executable:
#    chmod u+x cloudkeycert.sh
# 3. Create a certificate signing request (CSR) and private key
#    including the Subject Alternate Name (SAN) field.
#    Chrome will complain if the SAN field is missing.
#    There are many tools out there to create the CSR and
#    key file:
#    * - XCA (https://sourceforge.net/projects/xca/)
#    * - Digicert util (https://www.digicert.com/util/)
#    * - etc.
# 4. Have the CSR signed.
# 5. Ensure the signed certificate and key are in PEM (Base64) format
# 6. In the root home directory (/root), copy the signed cert
#    and key using the following names:
#    * - Certificate -> cloudkey.crt
#    * - Private Key -> cloudkey.key
# 7. Then run this script.  It will backup the existing files
#    in case you need to back out, copy the new files into place,
#    and update the keystore file.  It will stop/start the 
#    web server (NGINX) and the Unifi services.  You may need
#    to close your browser as it may not pick up on the fact that
#    the certificate changed...
#
# OpenSSL and Keytool options copied from script:
#    /usr/share/initramfs-tools/scripts/ubnt-bottom/configure-sslcert
# the only added option to the keytool was -noprompt to force
# overwriting the unifi alias rather than requiring the user
# to answer the prompt

HOSTCERTDIR=/etc/ssl/private
HOSTCERTTAR=cert.tar
HOSTCERTS="cloudkey.crt cloudkey.key unifi.keystore.jks"
BACKUPDIR="${HOSTCERTDIR}/`/bin/date +%Y%m%d`"
BACKUPFILE="`/bin/date +%Y%m%d%H%M`-cert.tar"

echo "Stopping the unifi service"
/usr/sbin/service unifi stop

echo "Stopping the NGINX web server"
/usr/sbin/service nginx stop

# Change to certificate directory
cd ${HOSTCERTDIR}

# Create a backup of the existing bits just in case
if [ ! -d ${BACKUPDIR} ]; then
        echo "Making directory ${BACKUPDIR}"
        mkdir ${BACKUPDIR}
fi

if [ ! -f ${HOSTCERTDIR}/${BACKUPFILE} ]; then
        echo "Creating tar ${BACKUPDIR}/${BACKUPFILE}"
        /bin/tar -cf ${BACKUPDIR}/${BACKUPFILE} ${HOSTCERTS}
fi

# Copy the certificate files from /root
/bin/cp /root/cloudkey.key ${HOSTCERTDIR}/
/bin/cp /root/cloudkey.crt ${HOSTCERTDIR}/

# Build the keystore file from the cloudkey.key and cloudkey.crt
/usr/bin/openssl pkcs12 -export -in ${HOSTCERTDIR}/cloudkey.crt -inkey ${HOSTCERTDIR}/cloudkey.key \
        -out /tmp/keystore.p12 -name unifi -password pass:'' && \
/usr/bin/keytool -importkeystore -deststorepass aircontrolenterprise \
        -destkeypass aircontrolenterprise -destkeystore ${HOSTCERTDIR}/unifi.keystore.jks \
        -srckeystore /tmp/keystore.p12 -srcstoretype PKCS12 -srcstorepass '' -alias unifi -noprompt

# Create the tar file after the keystore file is created
cd ${HOSTCERTDIR}
/bin/tar -cf ${HOSTCERTTAR} ${HOSTCERTS}


echo "Starting the NGINX web server"
/usr/sbin/service nginx start

echo "Starting the unifi service"
/usr/sbin/service unifi start

echo "You may need to restart your browser so it will notice the updated certificate"