`man chattr` says: "A file with the `a' attribute set can only be open in append mode for writing. Only the superuser or a process possessing the CAP_LINUX_IM

`man chattr` says: "A file with the `a' attribute set can only be open in append mode for writing. Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute."