Debian 11 couldn't determine device type, assuming default (plain)

[David Christensen <dpchrist@holgerdanske.com>]

debian-user:

I have:

2022-01-29 22:09:45 dpchrist@laalaa ~
$ cat /etc/debian_version ; uname -a
11.2
Linux laalaa 5.10.0-11-amd64 #1 SMP Debian 5.10.92-1 (2022-01-18) x86_64 
GNU/Linux


It has encrypted swap (and root), created by the Debian installer.

2022-01-29 22:14:17 dpchrist@laalaa ~
$ grep sdb2 /etc/crypttab
sdb2_crypt /dev/disk/by-partuuid/544032f5-02 /dev/urandom 
cipher=aes-xts-plain64,size=256,swap,discard


When I boot and enter the root passphrase, I see the following warning 
anywhere from two to a dozen or more times:

cryptsetup: WARNING: sdb2_crypt: couldn't determine device type, 
assuming default (plain)


What is causing the warning?


How do I fix whatever is causing problem(s), so that no warning is 
displayed?


David