bin/60526: dump(8) should warn before dumping r/w file systems w/o snapshot

["campbell+netbsd%mumble.net@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60526
>Category:       bin
>Synopsis:       dump(8) should warn before dumping r/w file systems w/o snapshot
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 01 17:45:00 +0000 2026
>Originator:     Taylor R Campbell
>Release:        current, 11, 10, 9, ..., 2
>Organization:
Acme Backup Dump Truck Crashes LLC
>Environment:
>Description:
dump(8) has -X and -x <snapdir> to make dumping from snapshots easy.

However, it is also easy to accidentally dump a live r/w file system.

Perhaps dump(8) should warn, or require an extra option, before doing that.

And perhaps it can suggest using -X/-x to make that more discoverable.
>How-To-Repeat:
dump -0af /backups/root.dump /
>Fix:
Yes, please.