Hi

Please find the successful test logs below:

# multipathd config
root@qau22c13n1:~# cat /etc/multipath.conf
defaults {
        find_multipaths yes
        user_friendly_names no
        reservation_key file
}

blacklist {
        devnode "^drbd[0-9]"
        device {
                vendor "VBOX"
                product "HARDDISK"
        }
}

blacklist_exceptions {
        device {
                vendor "FreeNAS"
                product "iSCSI Disk"
        }
}

# iscsi disk seen through 2 paths
root@qau22c13n1:~# multipath -l /dev/dm-15
36589cfc000000073fa706138358cd511 dm-15 TrueNAS,iSCSI Disk
size=16M features='0' hwhandler='1 alua' wp=rw
|-+- policy='service-time 0' prio=0 status=active
| `- 17:0:0:43 sdag 66:0   active undef running
`-+- policy='service-time 0' prio=0 status=enabled
  `- 16:0:0:43 sdab 65:176 active undef running

# no reservation key on disk
root@qau22c13n1:~# mpathpersist -i -k /dev/dm-15
  PR generation=0x0, 	0 registered reservation key.

# check for installed version
root@qau22c13n1:~# apt-cache policy multipath-tools
multipath-tools:
  Installed: 0.8.8-1ubuntu1.22.04.1
  Candidate: 0.8.8-1ubuntu1.22.04.1
  Version table:
 *** 0.8.8-1ubuntu1.22.04.1 500
        500 http://us.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu jammy-security/main amd64 Packages
        100 /var/lib/dpkg/status
     0.8.8-1ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu jammy/main amd64 Packages

# first try is failing as expected
root@qau22c13n1:~# mpathpersist -v2 --out --register-ignore --param-sark=0x214872831593209 /dev/dm-15
689.167643 | 36589cfc000000073fa706138358cd511: adding new path sdag
689.170397 | 36589cfc000000073fa706138358cd511: adding new path sdab
689.170519 | 36589cfc000000073fa706138358cd511: pr message=map 36589cfc000000073fa706138358cd511 setprkey key 214872831593209
689.170784 | 36589cfc000000073fa706138358cd511: message=map 36589cfc000000073fa706138358cd511 setprkey key 214872831593209 reply=map 36589cfc000000073fa706138358cd511 setprkey key 214872831593209: Missing argument
multipath-tools v0.8.8 (03/12, 2021)
CLI commands reference:
 list|show paths
 list|show paths format $format
 list|show paths raw format $format
 list|show path $path
 list|show maps|multipaths
 list|show status
 list|show daemon
 list|show maps|multipaths status
 list|show maps|multipaths stats
 list|show maps|multipaths format $format
 list|show maps|multipaths raw format $format
 list|show maps|multipaths topology
 list|show topology
 list|show maps|multipaths json
 list|show map|multipath $map topology
 list|show map|multipath $map format $format
 list|show map|multipath $map raw format $format
 list|show map|multipath $map json
 list|show config local
 list|show config
 list|show blacklist
 list|show devices
 list|show wildcards
 reset maps|multipaths stats
 reset map|multipath $map stats
 add path $path
 remove|del path $path
 add map|multipath $map
 remove|del map|multipath $map
 remove|del maps|multipaths
 switch|switchgroup map|multipath $map group $group
 reconfigure
 reconfigure all
 suspend map|multipath $map
 resume map|multipath $map
 resize map|multipath $map
 reload map|multipath $map
 reset map|multipath $map
 reinstate path $path
 fail path $path
 disablequeueing map|multipath $map
 restorequeueing map|multipath $map
 disablequeueing maps|multipaths
 restorequeueing maps|multipaths
 quit|exit
 shutdown
 getprstatus map|multipath $map
 setprstatus map|multipath $map
 unsetprstatus map|multipath $map
 forcequeueing daemon
 restorequeueing daemon
 getprkey map|multipath $map
 setprkey map|multipath $map key $key
 unsetprkey map|multipath $map
 setmarginal path $path
 unsetmarginal path $path
 unsetmarginal map|multipath $map

689.171680 | 36589cfc000000073fa706138358cd511: failed to set prkey for multipathd.
PR out: command failed
root@qau22c13n1:~# echo $?
13

# enabling -proposed packages
root@qau22c13n1:~# cat <<EOF >/etc/apt/sources.list.d/ubuntu-$(lsb_release -cs)-proposed.list
# Enable Ubuntu proposed archive
deb http://archive.ubuntu.com/ubuntu/ $(lsb_release -cs)-proposed restricted main multiverse universe
EOF

# updating apt cache
root@qau22c13n1:~# apt update
Get:1 http://archive.ubuntu.com/ubuntu jammy-proposed InRelease [270 kB]
Hit:2 https://ppa.launchpadcontent.net/linbit/linbit-drbd9-stack/ubuntu jammy InRelease                    
Hit:3 http://us.archive.ubuntu.com/ubuntu jammy InRelease                                                  
Hit:4 http://us.archive.ubuntu.com/ubuntu jammy-updates InRelease
Get:5 http://archive.ubuntu.com/ubuntu jammy-proposed/restricted amd64 Packages [147 kB]
Get:6 http://archive.ubuntu.com/ubuntu jammy-proposed/restricted Translation-en [26.2 kB]
Get:7 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages [124 kB]
Hit:8 http://us.archive.ubuntu.com/ubuntu jammy-backports InRelease
Get:9 http://archive.ubuntu.com/ubuntu jammy-proposed/main Translation-en [31.2 kB]
Get:10 http://archive.ubuntu.com/ubuntu jammy-proposed/multiverse amd64 Packages [23.4 kB]
Get:11 http://archive.ubuntu.com/ubuntu jammy-proposed/multiverse Translation-en [7804 B]
Get:12 http://archive.ubuntu.com/ubuntu jammy-proposed/universe amd64 Packages [50.4 kB]
Get:13 http://archive.ubuntu.com/ubuntu jammy-proposed/universe Translation-en [23.3 kB]
Hit:14 http://us.archive.ubuntu.com/ubuntu jammy-security InRelease
Fetched 704 kB in 1s (1045 kB/s)
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
32 packages can be upgraded. Run 'apt list --upgradable' to see them.

root@qau22c13n1:~# apt-cache policy multipath-tools
multipath-tools:
  Installed: 0.8.8-1ubuntu1.22.04.1
  Candidate: 0.8.8-1ubuntu1.22.04.2
  Version table:
     0.8.8-1ubuntu1.22.04.2 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
 *** 0.8.8-1ubuntu1.22.04.1 500
        500 http://us.archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu jammy-security/main amd64 Packages
        100 /var/lib/dpkg/status
     0.8.8-1ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu jammy/main amd64 Packages

# installing fixed package version from -proposed
root@qau22c13n1:~# sudo apt-get install multipath-tools/jammy-proposed
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Selected version '0.8.8-1ubuntu1.22.04.2' (Ubuntu:22.04/jammy-proposed [amd64]) for 'multipath-tools'
The following additional packages will be installed:
  kpartx
Suggested packages:
  multipath-tools-boot
The following packages will be upgraded:
  kpartx multipath-tools
2 upgraded, 0 newly installed, 0 to remove and 30 not upgraded.
Need to get 359 kB of archives.
After this operation, 3072 B disk space will be freed.
Do you want to continue? [Y/n] 
Get:1 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 kpartx amd64 0.8.8-1ubuntu1.22.04.2 [28.7 kB]
Get:2 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 multipath-tools amd64 0.8.8-1ubuntu1.22.04.2 [331 kB]
Fetched 359 kB in 1s (502 kB/s)         
(Reading database ... 62716 files and directories currently installed.)
Preparing to unpack .../kpartx_0.8.8-1ubuntu1.22.04.2_amd64.deb ...
Unpacking kpartx (0.8.8-1ubuntu1.22.04.2) over (0.8.8-1ubuntu1.22.04.1) ...
Preparing to unpack .../multipath-tools_0.8.8-1ubuntu1.22.04.2_amd64.deb ...
Unpacking multipath-tools (0.8.8-1ubuntu1.22.04.2) over (0.8.8-1ubuntu1.22.04.1) ...
Setting up kpartx (0.8.8-1ubuntu1.22.04.2) ...
Setting up multipath-tools (0.8.8-1ubuntu1.22.04.2) ...
Could not execute systemctl:  at /usr/bin/deb-systemd-invoke line 142.
Removing obsolete conffile /etc/init.d/multipath-tools ...
Processing triggers for man-db (2.10.2-1) ...
Processing triggers for libc-bin (2.35-0ubuntu3.1) ...
Scanning processes...                                                                                                                                                
Scanning candidates...                                                                                                                                               
Scanning linux images...                                                                                                                                             

Running kernel seems to be up-to-date.

Restarting services...
 systemctl restart multipathd.service

No containers need to be restarted.

No user sessions are running outdated binaries.

No VM guests are running outdated hypervisor (qemu) binaries on this host.

# no key registered
root@qau22c13n1:~# mpathpersist -i -k /dev/dm-15
  PR generation=0x0, 	0 registered reservation key.

# second try is working fine
root@qau22c13n1:~# mpathpersist -v2 --out --register-ignore --param-sark=0x214872831593209 /dev/dm-15
1104.293640 | 36589cfc000000073fa706138358cd511: adding new path sdag
1104.305762 | 36589cfc000000073fa706138358cd511: adding new path sdab
1104.306623 | 36589cfc000000073fa706138358cd511: pr message=setprkey map 36589cfc000000073fa706138358cd511 key 214872831593209
1104.307574 | 36589cfc000000073fa706138358cd511: message=setprkey map 36589cfc000000073fa706138358cd511 key 214872831593209 reply=ok

1104.312022 | 36589cfc000000073fa706138358cd511: pr message=setprstatus map 36589cfc000000073fa706138358cd511
1104.312688 | 36589cfc000000073fa706138358cd511: message=setprstatus map 36589cfc000000073fa706138358cd511 reply=ok

root@qau22c13n1:~# echo $?
0

# the key is correctly registered on both paths 
root@qau22c13n1:~# mpathpersist -i -k /dev/dm-15
  PR generation=0x2, 	2 registered reservation keys follow:
    0x214872831593209
    0x214872831593209
root@qau22c13n1:~#