最近需要SSL证书，又不想花钱买，正好看到linux基金会去年底上线了新的开源项目，免费推广SSL遂尝试。
Let's Encrypt 介绍
Let’s Encrypt is a free, automated, and open certificate authority (CA), run for the public’s benefit. It is a service provided by the Internet Security Research Group (ISRG).
We give people the digital certificates they need in order to enable HTTPS (SSL/TLS) for websites, for free, in the most user-friendly way we can. We do this because we want to create a more secure and privacy-respecting Web.
The key principles behind Let’s Encrypt are:
Free: Anyone who owns a domain name can use Let’s Encrypt to obtain a trusted certificate at zero cost.
Automatic: Software running on a web server can interact with Let’s Encrypt to painlessly obtain a certificate, securely configure it for use, and automatically take care of renewal.
Secure: Let’s Encrypt will serve as a platform for advancing TLS security best practices, both on the CA side and by helping site operators properly secure their servers.
Transparent: All certificates issued or revoked will be publicly recorded and available for anyone to inspect.
Open: The automatic issuance and renewal protocol will be published as an open standard that others can adopt.
Cooperative: Much like the underlying Internet protocols themselves, Let’s Encrypt is a joint effort to benefit the community, beyond the control of any one organization.
We have a page with more detailed information about how the Let’s Encrypt CA works.
以下内容来源于dockhub上的xataz/letsencrypt，有修改
1.编辑Dockerfile如下（部分内容来源于网络：xazta）
FROM alpine:3.5
ENV CERTBOT_VER v0.11.1
LABEL description="Letsencrypt based on alpine"
tags="latest 0.11.1 0.1"
maintainer="shawn.qian"
build_ver="2017022401"
RUN BUILD_DEPS="py2-pip
gcc
musl-dev
python2-dev
libffi-dev
openssl-dev"
&& apk add -U ${BUILD_DEPS}
tini
dialog
python
libssl1.0
&& pip install --no-cache virtualenv
&& virtualenv --no-site-packages -p python2 /usr/certbot/venv
&& /usr/certbot/venv/bin/pip install --no-cache-dir certbot==$CERTBOT_VER
&& pip uninstall --no-cache-dir -y virtualenv
&& apk del ${BUILD_DEPS}
&& rm -rf /var/cache/apk/* /root/.cache/pip
EXPOSE 80 443
VOLUME /etc/letsencrypt/
ENTRYPOINT ["/sbin/tini","--","/usr/certbot/venv/bin/certbot"]
CMD ["--help"]
保存文件，运行
docker build -t yourreposname/letsencrypt
安静等待build完成
2. 执行
sudo docker run -it --rm
-v /etc/letsencrypt:/etc/letsencrypt
-p 443:443 yourreposname/letsencrypt certonly
--standalone
--agree-tos
-m yourmailadd@mail.com
-d your.domain.com
P.S
1.本案例使用443端口，请保持你的443端口畅通，成功后会在/etc/letsencrypt下生成live/your.domain.com文件夹，里面就是你的证书文件了。
2. yourreposname/letsencrypt 其中"yourreposname"改成你的仓库名
cert.pem 申请的服务器证书文件
privkey.pem 服务器证书对应的私钥
chain.pem 除服务器证书外，浏览器解析所需的其他全部证书，比如根证书和中间证书
fullchain.pem 包含服务器证书的全部证书链文件