A file with the `i' attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be written to the file. Only the superuser or a process possessing the CAPLINUXIMMUTABLE capability can set or clear this attribute.
目测是被设置了 immutable 属性。
试试:
如果有这个 i 的话,
sudo chattr -i some_file
干掉它,然后就可以修改了。