So then you get impossibly fast write times, and boot disks that dont work, because they arent actually complete, if the user removes the disk when ddrescue reports that the operation is complete.
$ sudo ddrescue --force bodhi-6.0.0-64.iso /dev/sdb GNU ddrescue 1.23 Press Ctrl-C to interrupt ipos: 872349 kB, non-trimmed: 0 B, current rate: 727 MB/s opos: 872349 kB, non-scraped: 0 B, average rate: 436 MB/s non-tried: 0 B, bad-sector: 0 B, error rate: 0 B/s rescued: 872415 kB, bad areas: 0, run time: 1s pct rescued: 100.00%, read errors: 0, remaining time: n/a time since last successful read: n/a Finished Shown here, a 1 second run time, for a 700MB file to USB. But I already know this is impossible on my hardware. I'm just a dumb construction worker, but if i had to guess, ddrescue is listening to userspace libraries, rather than kernel signal processes. Here iostat reports: iostat -d Linux 5.15.0-56-generic (i) 01/10/2023 _x86_64_ (12 CPU) Device tps kB_read/s kB_wrtn/s kB_dscd/s kB_read kB_wrtn kB_dscd loop0 0.01 0.09 0.00 0.00 1133 0 0 loop1 0.01 0.09 0.00 0.00 1133 0 0 loop2 0.00 0.03 0.00 0.00 363 0 0 loop3 0.01 0.09 0.00 0.00 1090 0 0 loop4 0.01 0.04 0.00 0.00 439 0 0 loop5 0.01 0.04 0.00 0.00 438 0 0 sda 47.56 465.18 313.64 0.00 5574816 3758761 0 sdb 0.47 0.16 36.52 0.00 1932 437704 0 It appears from iostat, that the disk sdb is still being written, despite ddrescue reporting completion.