1. Testing restart on package upgrade
$ lxc launch ubuntu:jammy j --vm
$ lxc shell j
# pidof multipathd
2444
# echo "deb http://archive.ubuntu.com/ubuntu $(lsb_release -cs)-proposed restricted main multiverse universe" | sudo tee /etc/apt/sources.list.d/ubuntu-$(lsb_release -cs)-proposed.list
$ apt update -y && apt install -y multipath-tools -t $(lsb_release -cs)-proposed
<cut here>
Preparing to unpack .../kpartx_0.8.8-1ubuntu1.22.04.3_amd64.deb ...
Unpacking kpartx (0.8.8-1ubuntu1.22.04.3) over (0.8.8-1ubuntu1.22.04.1) ...
Preparing to unpack .../multipath-tools_0.8.8-1ubuntu1.22.04.3_amd64.deb ...
Unpacking multipath-tools (0.8.8-1ubuntu1.22.04.3) over (0.8.8-1ubuntu1.22.04.1) ...
Setting up kpartx (0.8.8-1ubuntu1.22.04.3) ...
Setting up multipath-tools (0.8.8-1ubuntu1.22.04.3) ...
The warning about having to reload systemd units can be safely ignored. Please see LP: #203509
8 for details.
Warning: The unit file, source configuration file or drop-ins of multipathd.service changed on
 disk. Run 'systemctl daemon-reload' to reload units.
Could not execute systemctl:  at /usr/bin/deb-systemd-invoke line 142.
Removing obsolete conffile /etc/init.d/multipath-tools ...
< cut here>
# pidof multipathd
3118
# systemctl status multipathd.{service,socket} | grep Active -B2
● multipathd.service - Device-Mapper Multipath Device Controller
     Loaded: loaded (/lib/systemd/system/multipathd.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-10-16 14:59:19 UTC; 37s ago
--
○ multipathd.socket - multipathd control socket
     Loaded: loaded (/lib/systemd/system/multipathd.socket; enabled; vendor preset: enabled)
     Active: inactive (dead) since Mon 2023-10-16 14:59:18 UTC; 38s ago

2. Downgrading
# apt install -y multipath-tools=0.8.8-1ubuntu1.22.04.1 --allow-downgrades
# pidof multipathd
3512
# systemctl status multipathd.{service,socket} | grep Active -B2
● multipathd.service - Device-Mapper Multipath Device Controller
     Loaded: loaded (/lib/systemd/system/multipathd.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-10-16 15:01:30 UTC; 29s ago
--
● multipathd.socket - multipathd control socket
     Loaded: loaded (/lib/systemd/system/multipathd.socket; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-10-16 15:01:29 UTC; 29s ago



3. Installing a fresh package (no warning message here because dpkg is lt-nl)
# apt purge multipath-tools -y
# apt install -y multipath-tools -t $(lsb_release -cs)-proposed
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Suggested packages:
  multipath-tools-boot
The following NEW packages will be installed:
  multipath-tools
0 upgraded, 1 newly installed, 0 to remove and 53 not upgraded.
Need to get 331 kB of archives.
After this operation, 1252 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 multipath-tools amd64 0.8.8-1ubuntu1.22.04.3 [331 kB]
Fetched 331 kB in 1s (461 kB/s)     
Selecting previously unselected package multipath-tools.
(Reading database ... 56636 files and directories currently installed.)
Preparing to unpack .../multipath-tools_0.8.8-1ubuntu1.22.04.3_amd64.deb ...
Unpacking multipath-tools (0.8.8-1ubuntu1.22.04.3) ...
Setting up multipath-tools (0.8.8-1ubuntu1.22.04.3) ...
Created symlink /etc/systemd/system/multipath-tools.service → /lib/systemd/system/multipathd.s
ervice.
Created symlink /etc/systemd/system/sysinit.target.wants/multipathd.service → /lib/systemd/sys
tem/multipathd.service.
Created symlink /etc/systemd/system/sockets.target.wants/multipathd.socket → /lib/systemd/syst
em/multipathd.socket.
Could not execute systemctl:  at /usr/bin/deb-systemd-invoke line 142.
Processing triggers for man-db (2.10.2-1) ...
Processing triggers for libc-bin (2.35-0ubuntu3.4) ...
Scanning processes...                                                                         
Scanning linux images...                                                                      

Running kernel seems to be up-to-date.

No services need to be restarted.

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.

# systemctl status multipathd.{service,socket} | grep Active -B2
● multipathd.service - Device-Mapper Multipath Device Controller
     Loaded: loaded (/lib/systemd/system/multipathd.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-10-16 15:03:20 UTC; 15min ago
--
○ multipathd.socket - multipathd control socket
     Loaded: loaded (/lib/systemd/system/multipathd.socket; enabled; vendor preset: enabled)
     Active: inactive (dead)


4. Upgrading to a future package
# wget https://launchpad.net/ubuntu/+archive/primary/+files/kpartx_0.8.8-1ubuntu1.22.04.3_amd64.deb
# wget https://launchpad.net/ubuntu/+archive/primary/+files/multipath-tools_0.8.8-1ubuntu1.22.04.3_amd64.deb
# mkdir tmp
# dpkg-deb -R multipath-tools_0.8.8-1ubuntu1.22.04.3_amd64.deb tmp/
# sed -i s/1ubuntu1.22.04.3/1ubuntu1.22.04.4/g tmp/DEBIAN/control
# dpkg-deb -b tmp/ mpath22.04.4.deb
# mkdir kpartxtmp
# dpkg-deb -R kpartx_0.8.8-1ubuntu1.22.04.3_amd64.deb kpartxtmp/
# sed -i s/1ubuntu1.22.04.3/1ubuntu1.22.04.4/g kpartxtmp/DEBIAN/control
# dpkg-deb -b kpartxtmp/ kpartx22.04.4.deb
# dpkg -i kpartx22.04.4.deb
# dpkg -i mpath22.04.4.deb
# dpkg -l multipath-tools | grep multipath-tools | awk '{print $3}'
0.8.8-1ubuntu1.22.04.4
# systemctl status multipathd.{service,socket} | grep Active -B2
● multipathd.service - Device-Mapper Multipath Device Controller
     Loaded: loaded (/lib/systemd/system/multipathd.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-10-16 15:33:03 UTC; 5s ago
--
○ multipathd.socket - multipathd control socket
     Loaded: loaded (/lib/systemd/system/multipathd.socket; enabled; vendor preset: enabled)
     Active: inactive (dead)


5. Testing multipath-tools functionality after upgading from current main
# apt purge multipath-tools
# apt install -y multipath-tools=0.8.8-1ubuntu1.22.04.1
# apt install -y lsscsi open-iscsi tgt
Copy the following lines to a script and execute it

```
targetname="iqn.2016-11.foo.com:target.iscsi"
cwd=$(pwd)
testdir="/mnt/tgtmpathtest"
localhost="127.0.0.1"
portal="${localhost}:3260"
maxpaths=4
backfn="backingfile"
expectwwid="60000000000000000e00000000010001"
testdisk="/dev/disk/by-id/wwn-0x${expectwwid}"
### Setup mpath devices
# Restart tgtd to make sure modules are all loaded
service tgt restart || echo "Failed to restart tgt" >&2
# prep SINGLE test file
truncate --size 100M ${backfn}
# create target
tgtadm --lld iscsi --op new --mode target --tid 1 -T "${targetname}"
# allow all to bind the target
tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL
# set backing file
tgtadm --lld iscsi --op new --mode logicalunit --tid 1 --lun 1 -b "${cwd}/${backfn}"
# scan for targets (locally)
iscsiadm --mode discovery --type sendtargets --portal ${localhost}
# login
echo "login #1"
iscsiadm --mode node --targetname "${targetname}" --portal ${portal} --login
# duplicate this session (always 1)
for i in $(seq 2 ${maxpaths})
do
    echo "extra login #${i}"
    iscsiadm --mode session -r 1 --op new
done
udevadm settle
sleep 5 # sleep a bit to allow device to be created.
# status summary
echo "Status after initial setup"
tgtadm --lld iscsi --mode target --op show
tgtadm --lld iscsi --op show --mode conn --tid 1
iscsiadm --mode session -P 1
lsscsi -liv
multipath -v3 -ll
dmsetup table
echo "Test WWN should now point to DM"
readlink "${testdisk}" | grep dm
```

# multipath -ll
mpatha (360000000000000000e00000000010001) dm-0 IET,VIRTUAL-DISK
size=100M features='0' hwhandler='0' wp=rw
|-+- policy='service-time 0' prio=1 status=active
| `- 8:0:0:1  sdc 8:32 active ready running
|-+- policy='service-time 0' prio=1 status=enabled
| `- 7:0:0:1  sdb 8:16 active ready running
|-+- policy='service-time 0' prio=1 status=enabled
| `- 10:0:0:1 sde 8:64 active ready running
`-+- policy='service-time 0' prio=1 status=enabled
  `- 9:0:0:1  sdd 8:48 active ready running
# lsblk
NAME     MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
loop0      7:0    0  40.8M  1 loop  /snap/snapd/20092
loop1      7:1    0 111.9M  1 loop  /snap/lxd/24322
loop2      7:2    0  63.5M  1 loop  /snap/core20/2015
sda        8:0    0    10G  0 disk  
├─sda1     8:1    0   9.9G  0 part  /
├─sda14    8:14   0     4M  0 part  
└─sda15    8:15   0   106M  0 part  /boot/efi
sdb        8:16   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
sdc        8:32   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
sdd        8:48   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
sde        8:64   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
# apt install -y multipath-tools -t $(lsb_release -cs)-proposed
# dpkg -l multipath-tools | grep multipath-tools | awk '{print $3}'
0.8.8-1ubuntu1.22.04.3
# multipath -ll
mpatha (360000000000000000e00000000010001) dm-0 IET,VIRTUAL-DISK
size=100M features='0' hwhandler='0' wp=rw
|-+- policy='service-time 0' prio=1 status=active
| `- 8:0:0:1  sdc 8:32 active ready running
|-+- policy='service-time 0' prio=1 status=enabled
| `- 7:0:0:1  sdb 8:16 active ready running
|-+- policy='service-time 0' prio=1 status=enabled
| `- 10:0:0:1 sde 8:64 active ready running
`-+- policy='service-time 0' prio=1 status=enabled
  `- 9:0:0:1  sdd 8:48 active ready running
root@j:~# lsblk
NAME     MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
loop0      7:0    0  40.8M  1 loop  /snap/snapd/20092
loop1      7:1    0 111.9M  1 loop  /snap/lxd/24322
loop2      7:2    0  63.5M  1 loop  /snap/core20/2015
sda        8:0    0    10G  0 disk  
├─sda1     8:1    0   9.9G  0 part  /
├─sda14    8:14   0     4M  0 part  
└─sda15    8:15   0   106M  0 part  /boot/efi
sdb        8:16   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
sdc        8:32   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
sdd        8:48   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath 
sde        8:64   0   100M  0 disk  
└─mpatha 253:0    0   100M  0 mpath