[mythtv-users] troublesome mariadb update, ubuntu 20.04

[lists at arewethere.net]

Just in case this hits someone else.
I sorted this out but not sure of the most straightforward path.
Waiting a good long interval between commands seems to help with
forward progress.

We start innocently enough

# apt upgrade ...ho hum...

Unpacking mariadb-server-10.3 (1:10.3.32-0ubuntu0.20.04.1)
  over (1:10.3.31-0ubuntu0.20.04.1) ...

But then.

# mythtv-status
Total disk space is 0 MB, I can't use that to calculate a percentage!
Illegal division by zero at /usr/bin/mythtv-status line 605.

oh.

# systemctl status mythtv-backend
 mythtv-backend.service - MythTV Backend
     Loaded: loaded (/lib/systemd/system/mythtv-backend.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2021-11-15 14:10:42 AEDT; 3 weeks 2 days ago
       Docs: https://www.mythtv.org/wiki/Mythbackend
   Main PID: 1678 (mythbackend)
      Tasks: 38 (limit: 9370)
     Memory: 3.1G
     CGroup: /system.slice/mythtv-backend.service
             └─1678 /usr/bin/mythbackend --quiet --syslog local7

Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdbcon.cpp:830 (prepare) Driver > QMYSQL3: Unable to prepare statement
                                              Database error was:
Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdb.cpp:181 (DBError) DB Error (>
                                              Query was:
                                              DELETE FROM settings WHERE value = 'MusicStreamListModified' AND hos>
                                              Bindings were:
                                              :HOSTNAME="tvbox", :KEY="MusicStreamListModified"
                                              Driver error was [2/0]:
                                              QMYSQL: Unable to execute query
                                              Database error was:
Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdb.cpp:352 (SaveSettingOnHost) >
Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdbcon.cpp:828 (prepare) Error p>
Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdbcon.cpp:830 (prepare) Driver > QMYSQL3: Unable to prepare statement
                                              Database error was:
Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdbcon.cpp:828 (prepare) Error p>
Dec 08 21:12:02 tvbox mythbackend[1678]: mythbackend[1678]: E CoreContext mythdbcon.cpp:830 (prepare) Driver >
                                              QMYSQL3: Unable to prepare statement
                                              Database error was:
Dec 08 21:12:11 tvbox mythbackend[1678]: mythbackend[1678]: E JobQueue mythdbcon.cpp:828 (prepare) Error prep>
Dec 08 21:12:11 tvbox mythbackend[1678]: mythbackend[1678]: E JobQueue mythdbcon.cpp:830 (prepare) Driver err> QMYSQL3: Unable to prepare statement
                                              Database error was:
Dec 08 21:12:11 tvbox mythbackend[1678]: mythbackend[1678]: E JobQueue mythdb.cpp:181 (DBError) DB Error (Err>
                                              Query was:
                                              SELECT j.id, j.chanid, j.starttime, j.inserttime, j.type, j.cmds, j.>
                                              Driver error was [2/0]:
                                              QMYSQL: Unable to execute query
                                              Database error was:



# systemctl stop mysql
# systemctl count-to-ten
# systemctl start mysql
# systemctl status mysql
  ... all green this time

# systemctl count-to-ten-again
# systemctl restart mythtv-backend
echo $?
0

# systemctl status mythtv-backend
 mythtv-backend.service - MythTV Backend
     Loaded: loaded (/lib/systemd/system/mythtv-backend.service; enabled; vendor preset: enabled)
     Active: active (running) since Wed 2021-12-08 21:13:16 AEDT; 18s ago
       Docs: https://www.mythtv.org/wiki/Mythbackend
   Main PID: 521922 (mythbackend)
      Tasks: 22 (limit: 9370)
     Memory: 15.4M
     CGroup: /system.slice/mythtv-backend.service
             └─521922 /usr/bin/mythbackend --quiet --syslog local7

Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext housekeeper.cpp:663 (RegisterTa>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext housekeeper.cpp:663 (RegisterTa>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext housekeeper.cpp:663 (RegisterTa>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext housekeeper.cpp:737 (Start) Sta>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext serverpool.cpp:418 (listen) Lis>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext serverpool.cpp:418 (listen) Lis>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext serverpool.cpp:418 (listen) Lis>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext serverpool.cpp:418 (listen) Lis>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext serverpool.cpp:418 (listen) Lis>
Dec 08 21:13:33 tvbox mythbackend[521922]: mythbackend[521922]: I CoreContext serverpool.cpp:418 (listen) Lis>

# systemctl count-to-ten-once-more
# mythtv-status

MythTV status for localhost
===========================
Status as of.....: 2021-12-08 21:13:57
Total Disk Space.: Total space is 7.3 TB, with 4.7 TB used (65%)
Next Recording In: 8 Hours, 14 Minutes

Scheduled Recordings:
...all good now