But of course, like any immutable system, there are mutable parts (otherwise, we couldn’t create any configuration files). OSTree handles this with “overlays” (actually, we use OverlayFS) that allow a read-write filesystem to be layered on top of the immutable system. For example, the /etc and /var directories are writable, while the rest of the system is read-only.
But what if it’s not fine? Even back in 1996, before a single component of the ISS was launched into orbit, NASA foresaw the possibility of an even worse worst-case scenario: an uncontrolled reentry. The crux of this scenario involves multiple systems failing in an improbable but not completely impossible cascade. Cabin depressurization could damage the avionics. The electrical power system could go offline, along with thermal control and data handling. Without these, systems controlling coolant and even propellant could break down. Unmoored, the ISS would edge slowly toward Earth, maybe over a year or two, with no way to control where it is headed or where its debris might land. And no, we could not save ourselves by blowing the station up. This would be extremely dangerous and almost certainly create an enormous amount of space trash—which is how we got into this hypothetical mess in the first place.，更多细节参见新收录的资料
，详情可参考新收录的资料
В России ответили на имитирующие высадку на Украине учения НАТО18:04
then \p{utf8}&~(a) means “not a, but only valid UTF-8”. no special byte-boundary logic, just another constraint composed into the pattern.。新收录的资料对此有专业解读