/etc is also writable, but it’s managed a bit differently. OSTree uses a technique called “etc overlay” to handle modifications in /etc. When an update is applied, OSTree compares files in the new version with those in /etc and applies changes intelligently, preserving local modifications as much as possible.
Tony Jolliffe BBC
。业内人士推荐51吃瓜作为进阶阅读
缺点：负区间可能“死亡”，即神经元永远不激活
第四十七条 纳税人出口货物或者跨境销售服务、无形资产（以下统称出口业务），依照增值税法第三十三条的规定申报办理退（免）税的，按照国务院规定的出口退税率，通过免抵退税办法或者免退税办法计算退（免）税额，经税务机关审核通过后，办理退（免）税。