Exposed in the dracut testsuite while adding tests for sysexts:
```
[ 2.972948] localhost (sd-merge)[510]: Validation of dm-verity signature failed via the kernel, trying userspace validation instead: Required key not available
[ 2.972993] localhost (sd-merge)[510]: Skipping file '/etc/verity.d/dracut.pem', suffix is not '.crt'.
[ 2.973045] localhost (sd-merge)[510]: No userspace dm-verity certificates found.
```
<term><varname>systemd.allow_userspace_verity=</varname></term>
<listitem><para>Takes a boolean argument. Controls whether disk images that are Verity protected may
- be authenticated in userspace signature checks via <filename>/etc/verity.d/</filename> (and related
- directories) public key drop-ins, or whether in-kernel signature checking only. Defaults to
+ be authenticated in userspace signature checks via <filename>/etc/verity.d/*.crt</filename> (and
+ related directories) public key drop-ins, or whether in-kernel signature checking only. Defaults to
on.</para>
<xi:include href="version-info.xml" xpointer="v256"/></listitem>
<filename>/usr/lib/</filename> it is assumed to be trusted.</para></listitem>
<listitem><para>If the disk image contains a Verity enabled disk image, along with a signature
- partition with a key in the kernel keyring or in <filename>/etc/verity.d/</filename> (and related
+ partition with a key in the kernel keyring or in <filename>/etc/verity.d/*.crt</filename> (and related
directories) the disk image is considered trusted.</para></listitem>
</orderedlist>