Comment 9 for bug 2051153

Verification part II:
upgrade to proposed, then also re-install (to showcase future updates)
You can see that this update not only finally works, but also correctly backs up the former version (there is nothing we can do for former former versions).

root@j-vm:~# apt-cache policy qemu-block-extra; apt install -y --reinstall qemu-block-extra; systemctl status run-qemu.mount; ls -laF /run/qemu/
qemu-block-extra:
  Installed: 1:6.2+dfsg-2ubuntu6.16
  Candidate: 1:6.2+dfsg-2ubuntu6.17
  Version table:
     1:6.2+dfsg-2ubuntu6.17 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
 *** 1:6.2+dfsg-2ubuntu6.16 500
        500 http://archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu jammy-security/main amd64 Packages
        100 /var/lib/dpkg/status
     1:6.2+dfsg-2ubuntu6 500
        500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  qemu-system-common qemu-system-data qemu-system-gui qemu-system-x86 qemu-utils
Suggested packages:
  samba vde2 debootstrap
The following packages will be upgraded:
  qemu-block-extra qemu-system-common qemu-system-data qemu-system-gui qemu-system-x86 qemu-utils
6 upgraded, 0 newly installed, 0 to remove and 40 not upgraded.
Need to get 15.4 MB of archives.
After this operation, 5120 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-system-gui amd64 1:6.2+dfsg-2ubuntu6.17 [220 kB]
Get:2 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-block-extra amd64 1:6.2+dfsg-2ubuntu6.17 [68.1 kB]
Get:3 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-system-x86 amd64 1:6.2+dfsg-2ubuntu6.17 [10.1 MB]
Get:4 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-system-common amd64 1:6.2+dfsg-2ubuntu6.17 [2047 kB]
Get:5 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-utils amd64 1:6.2+dfsg-2ubuntu6.17 [1525 kB]
Get:6 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-system-data all 1:6.2+dfsg-2ubuntu6.17 [1431 kB]
Fetched 15.4 MB in 3s (5868 kB/s)
(Reading database ... 72988 files and directories currently installed.)
Preparing to unpack .../0-qemu-system-gui_1%3a6.2+dfsg-2ubuntu6.17_amd64.deb ...
Unpacking qemu-system-gui (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.16) ...
Preparing to unpack .../1-qemu-block-extra_1%3a6.2+dfsg-2ubuntu6.17_amd64.deb ...
Unpacking qemu-block-extra (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.16) ...
Preparing to unpack .../2-qemu-system-x86_1%3a6.2+dfsg-2ubuntu6.17_amd64.deb ...
Unpacking qemu-system-x86 (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.16) ...
Preparing to unpack .../3-qemu-system-common_1%3a6.2+dfsg-2ubuntu6.17_amd64.deb ...
Unpacking qemu-system-common (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.16) ...
Preparing to unpack .../4-qemu-utils_1%3a6.2+dfsg-2ubuntu6.17_amd64.deb ...
Unpacking qemu-utils (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.16) ...
Preparing to unpack .../5-qemu-system-data_1%3a6.2+dfsg-2ubuntu6.17_all.deb ...
Unpacking qemu-system-data (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.16) ...
Setting up qemu-system-common (1:6.2+dfsg-2ubuntu6.17) ...
Setting up qemu-system-data (1:6.2+dfsg-2ubuntu6.17) ...
Setting up qemu-utils (1:6.2+dfsg-2ubuntu6.17) ...
Setting up qemu-block-extra (1:6.2+dfsg-2ubuntu6.17) ...
Setting up qemu-system-x86 (1:6.2+dfsg-2ubuntu6.17) ...
Setting up qemu-system-gui (1:6.2+dfsg-2ubuntu6.17) ...
Processing triggers for hicolor-icon-theme (0.17-2) ...
Processing triggers for man-db (2.10.2-1) ...
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.
● run-qemu.mount - Prepare /run/qemu to allow still running qemu binaries of former builds (after package upgrades) to fallback-load modules from there
     Loaded: loaded (/proc/self/mountinfo; enabled; vendor preset: enabled)
     Active: active (mounted) since Mon 2024-02-05 10:40:29 UTC; 2min 0s ago
      Where: /run/qemu
       What: tmpfs
      Tasks: 0 (limit: 1171)
     Memory: 8.0K
        CPU: 2ms
     CGroup: /system.slice/run-qemu.mount

Feb 05 10:40:29 j-vm systemd[1]: Mounting Prepare /run/qemu to allow still running qemu binaries of former builds (after package upgrades) to fallback-load modules from there...
Feb 05 10:40:29 j-vm systemd[1]: Mounted Prepare /run/qemu to allow still running qemu binaries of former builds (after package upgrades) to fallback-load modules from there.
total 0
drwxr-xr-x 3 root root 60 Feb 5 10:42 ./
drwxr-xr-x 29 root root 840 Feb 5 10:38 ../
drwxr-xr-x 2 root root 140 Feb 5 10:42 Debian_1_6.2+dfsg-2ubuntu6.16/
root@j-vm:~# sleep 10s
root@j-vm:~# apt-cache policy qemu-block-extra; apt install -y --reinstall qemu-block-extra; systemctl status run-qemu.mount; ls -laF /run/qemu/
qemu-block-extra:
  Installed: 1:6.2+dfsg-2ubuntu6.17
  Candidate: 1:6.2+dfsg-2ubuntu6.17
  Version table:
 *** 1:6.2+dfsg-2ubuntu6.17 500
        500 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1:6.2+dfsg-2ubuntu6.16 500
        500 http://archive.ubuntu.com/ubuntu jammy-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu jammy-security/main amd64 Packages
     1:6.2+dfsg-2ubuntu6 500
        500 http://archive.ubuntu.com/ubuntu jammy/main amd64 Packages
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 40 not upgraded.
Need to get 68.1 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu jammy-proposed/main amd64 qemu-block-extra amd64 1:6.2+dfsg-2ubuntu6.17 [68.1 kB]
Fetched 68.1 kB in 0s (144 kB/s)
(Reading database ... 72988 files and directories currently installed.)
Preparing to unpack .../qemu-block-extra_1%3a6.2+dfsg-2ubuntu6.17_amd64.deb ...
Unpacking qemu-block-extra (1:6.2+dfsg-2ubuntu6.17) over (1:6.2+dfsg-2ubuntu6.17) ...
Setting up qemu-block-extra (1:6.2+dfsg-2ubuntu6.17) ...
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.
● run-qemu.mount - Prepare /run/qemu to allow still running qemu binaries of former builds (after package upgrades) to fallback-load modules from there
     Loaded: loaded (/proc/self/mountinfo; enabled; vendor preset: enabled)
     Active: active (mounted) since Mon 2024-02-05 10:40:29 UTC; 2min 52s ago
      Where: /run/qemu
       What: tmpfs
      Tasks: 0 (limit: 1171)
     Memory: 8.0K
        CPU: 2ms
     CGroup: /system.slice/run-qemu.mount

Feb 05 10:40:29 j-vm systemd[1]: Mounting Prepare /run/qemu to allow still running qemu binaries of former builds (after package upgrades) to fallback-load modules from there...
Feb 05 10:40:29 j-vm systemd[1]: Mounted Prepare /run/qemu to allow still running qemu binaries of former builds (after package upgrades) to fallback-load modules from there.
total 0
drwxr-xr-x 4 root root 80 Feb 5 10:43 ./
drwxr-xr-x 29 root root 840 Feb 5 10:38 ../
drwxr-xr-x 2 root root 140 Feb 5 10:42 Debian_1_6.2+dfsg-2ubuntu6.16/
drwxr-xr-x 2 root root 140 Feb 5 10:43 Debian_1_6.2+dfsg-2ubuntu6.17/

Overall this verified that it works again.