On Sun, 12 Mar 2023 22:47:39 -0400
Steve Litt <slitt@???> wrote:

> The preceding confuses me a little because my first instinct would be
> that sync wouldn't work on a read-only filesystem, because what sync
> does is write cached disk writes to disk. A quick web search yielded
> nothing on this subject. But perhaps sync *does* work on readonly
> filesystems. If that's the case, leaving out the sync would leave
> cached writes and perhaps would trigger a journal recovery on the next
> reboot. So if you haven't yet, but a sync command after you've
> unmounted all disk partitions and set the root partition read-only.

I recall being confused when I learned about SysRq-REISUB because I
also found references to SysRq-REISUSB where S is Sync.

-

https://en.wikipedia.org/wiki/Magic_SysRq_key

unRaw
tErminate (SIGTERM to all)
kIll      (SIGKILL to all)
Sync
Unmount      (remount all as read-only)
reBoot