Thank you Brian for accepting it into impish-proposed! I've tested usrmerge 25ubuntu1.1 from impish-proposed, all good: $ lxc launch ubuntu:bionic usrmerge $ lxc exec usrmerge bash # do-release-upgrade [...] # reboot # ls -l / total 88 drwxr-xr-x 2 root root 12288 Oct 27 13:39 bin drwxr-xr-x 2 root root 4096 Oct 21 15:54 boot drwxr-xr-x 8 root root 500 Oct 27 13:39 dev drwxr-xr-x 94 root root 12288 Oct 27 13:39 etc drwxr-xr-x 3 root root 4096 Oct 27 13:30 home drwxr-xr-x 21 root root 4096 Oct 27 13:35 lib drwxr-xr-x 2 root root 4096 Oct 27 13:31 lib64 drwxr-xr-x 2 root root 4096 Oct 21 15:48 media drwxr-xr-x 2 root root 4096 Oct 21 15:48 mnt drwxr-xr-x 2 root root 4096 Oct 21 15:48 opt dr-xr-xr-x 512 nobody nogroup 0 Oct 27 13:39 proc drwx------ 4 root root 4096 Oct 27 13:39 root drwxr-xr-x 20 root root 640 Oct 27 13:39 run drwxr-xr-x 2 root root 12288 Oct 27 13:39 sbin drwxr-xr-x 6 root root 4096 Oct 27 13:35 snap drwxr-xr-x 2 root root 4096 Oct 21 15:48 srv dr-xr-xr-x 13 nobody nogroup 0 Oct 27 13:39 sys drwxrwxrwt 10 root root 4096 Oct 27 13:39 tmp drwxr-xr-x 12 root root 4096 Oct 27 13:33 usr drwxr-xr-x 13 root root 4096 Oct 21 15:52 var # mkdir -p /usr/lib/udev && cp /lib/udev/hwdb.bin /usr/lib/udev/ # sed -i 's/Prompt=lts/Prompt=normal/' /etc/update-manager/release-upgrades # do-release-upgrade [...] # /usr/lib/usrmerge/convert-usrmerge ionice: ioprio_set failed: Operation not permitted chrt: failed to set pid 44628's policy: Operation not permitted FATAL ERROR: Both /lib/udev/hwdb.bin and /usr/lib/udev/hwdb.bin exist. You can try correcting the errors reported and running again /usr/lib/usrmerge/convert-usrmerge until it will complete without errors. Do not install or update other Debian packages until the program has been run successfully. # echo $? 1 # wget https://launchpad.net/ubuntu/+archive/primary/+files/usrmerge_25ubuntu1.1_all.deb # dpkg -i usrmerge_25ubuntu1.1_all.deb (Reading database ... 35984 files and directories currently installed.) Preparing to unpack usrmerge_25ubuntu1.1_all.deb ... Unpacking usrmerge (25ubuntu1.1) over (24ubuntu3) ... Setting up usrmerge (25ubuntu1.1) ... Smartmatch is experimental at /usr/lib/usrmerge/convert-usrmerge line 172. ionice: ioprio_set failed: Operation not permitted chrt: failed to set pid 44665's policy: Operation not permitted The system has been successfully converted. # /usr/lib/usrmerge/convert-usrmerge Smartmatch is experimental at /usr/lib/usrmerge/convert-usrmerge line 172. ionice: ioprio_set failed: Operation not permitted chrt: failed to set pid 44812's policy: Operation not permitted The system has been successfully converted. # echo $? 0 # ls -la / total 64 drwxr-xr-x 18 root root 4096 Oct 27 13:53 . drwxr-xr-x 18 root root 4096 Oct 27 13:53 .. lrwxrwxrwx 1 root root 7 Oct 27 13:53 bin -> usr/bin drwxr-xr-x 2 root root 4096 Oct 21 15:54 boot drwxr-xr-x 8 root root 500 Oct 27 13:39 dev drwxr-xr-x 101 root root 12288 Oct 27 13:53 etc drwxr-xr-x 3 root root 4096 Oct 27 13:30 home lrwxrwxrwx 1 root root 7 Oct 27 13:53 lib -> usr/lib lrwxrwxrwx 1 root root 9 Oct 27 13:53 lib32 -> usr/lib32 lrwxrwxrwx 1 root root 9 Oct 27 13:53 lib64 -> usr/lib64 lrwxrwxrwx 1 root root 10 Oct 27 13:53 libx32 -> usr/libx32 drwxr-xr-x 2 root root 4096 Oct 21 15:48 media drwxr-xr-x 2 root root 4096 Oct 21 15:48 mnt drwxr-xr-x 2 root root 4096 Oct 21 15:48 opt dr-xr-xr-x 493 nobody nogroup 0 Oct 27 13:39 proc drwx------ 4 root root 4096 Oct 27 13:53 root drwxr-xr-x 24 root root 800 Oct 27 13:50 run lrwxrwxrwx 1 root root 8 Oct 27 13:53 sbin -> usr/sbin drwxr-xr-x 6 root root 4096 Oct 27 13:35 snap drwxr-xr-x 2 root root 4096 Oct 21 15:48 srv dr-xr-xr-x 13 nobody nogroup 0 Oct 27 13:39 sys drwxrwxrwt 11 root root 4096 Oct 27 13:51 tmp drwxr-xr-x 15 root root 4096 Oct 27 13:47 usr drwxr-xr-x 13 root root 4096 Oct 21 15:52 var