回答:
あなたが欲しいupdate-rc.d mysql disable
。update-rc.dマンページで述べたように、削除したくない場合:
A common system administration error is to delete the links with the
thought that this will "disable" the service, i.e., that this will pre‐
vent the service from being started. However, if all links have been
deleted then the next time the package is upgraded, the package's
postinst script will run update-rc.d again and this will reinstall
links at their factory default locations
Debian 8(Jessy)はデフォルトでsystemdを使用しているため、これを試してください。
systemctl list-units | grep mysql # check for mysql unit name
systemctl disable mysql.service # or whatever you find at prev step