1、停止服务

service zabbix-server stop

2、新建快照

3、备份配置、zabbix文件

 mkdir /home/vica/zabbix-backup/
 cp /etc/zabbix/zabbix_server.conf /home/vica/zabbix-backup/
 cp /etc/apache2/conf-enabled/zabbix.conf /home/vica/zabbix-backup/
 cp -R /usr/share/zabbix/ /home/vica/zabbix-backup/
 cp -R /usr/share/doc/zabbix-* /home/vica/zabbix-backup/

4、 Debian 8更新repository 配置（删除→安装）

rm -Rf /etc/apt/sources.list.d/zabbix.list
wget https://repo.zabbix.com/zabbix/4.0/debian/pool/main/z/zabbix-release/zabbix-release_4.0-2+jessie_all.deb
dpkg -i zabbix-release_4.0-2+jessie_all.deb

5、升级zabbix组件

apt update
apt-get install --only-upgrade zabbix-server-mysql zabbix-frontend-php zabbix-agent

6、启动zabbix组件

service zabbix-server start
service zabbix-proxy start
service zabbix-agent start

后续Tips：
升级后访问页面报错

Database error The frontend does not match Zabbix database. Current database version (mandatory/optional): 3010047/3010047. Required mandatory version: 4000000. Contact your system administrator.

手动修改版本

update dbversion set mandatory=4000000;

zabbix4.0字体路径(graphfont.ttf)
/usr/share/zabbix/assets/fonts/