如何删除快照？apt 假装它不在那里，但我仍然可以用它调用命令。
试图 rm 它说“只读文件系统”
root@tunnel:/# apt remove snap
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package 'snap' is not installed, so not removed
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@tunnel:/# snap whoami
email: -