想在docker中使用Flexmonster，但是在配置环境后，发现Flexmonster需要使用systemctl来管理服务，然而在docker容器中没有systemctl可用，于是开始折腾之旅！
以下是解决办法：
1、下载systemctl
wget https://raw.githubusercontent.com/gdraheim/docker-systemctl-replacement/master/files/docker/systemctl.py
2、修改dockerfile
#安装wget
USER root
ARG INSTALL_WGET=true
RUN if [ ${INSTALL_WGET} = true ]; then \
apt-get install -y wget \
;fi
#build镜像时将当前目录中下载的systemctl.py文件拷贝到镜像/bin/systemctl，记得要将下载来的systemctl.py文件放到当前build目录，或修改dockerfile
#------------------------------------------------------------------------
# systemctl
#------------------------------------------------------------------------
USER root
ARG INSTALL_SYSTEMCTL=true
COPY ./systemctl.py /bin/systemctl
RUN if [ ${INSTALL_SYSTEMCTL} = true ]; then \
chmod +x /bin/systemctl \
;fi
#在镜像中安装python，因为默认镜像中没有安装python
USER root
ARG INSTALL_PYTHON=true
RUN if [ ${INSTALL_PYTHON} = true ]; then \
apt-get install python \
;fi
#给镜像安装sudo命令，因为镜像默认使用root，未安装sudo命令
ARG INSTALL_SUDO=true
RUN if [ ${INSTALL_SUDO} = true ]; then \
apt-get install sudo \
;fi
3、build镜像