Full Distro Upgrade (18.04 -> 20.04) stops in mysql upgrade script (5.7 -> 8.0). Reboots fall into Grub Rescue. Error: package mysql-server-8.0 8.0.21-0ubuntu0.20.04.4 failed to install/upgrade: installed mysql-server-8.0 package post-installation script subprocess returned error exit status 1

[Eduardo Bonato]

Bug Use Case:
1) You had updated everything using apt-get update/upgrade and dist-upgrade.
2) You are upgrading an Azure VM on 18.04-LTS to 20.04, using do-release-upgrade script. This will also upgrade your mysql from 5.7 to 8.0.
3) You are using mysql service with datadir in a different path (most common scenario) and tuned your mysqld.cnf
4) You reached the end of do-release-upgrade script, but mysql package has not upgraded due this error captured by this send report bug tool.
5) If you decide to reboot VM at end of do-release-upgrade, without resolve this error with mysql package, you will get your VM stuck at boot screen, at grub rescue console (which is incessesible by remote vm).
6) You can recover your VM using steps described in https://docs.microsoft.com/en-us/answers/questions/72418/problem-with-starting-on-of-my-azure-ubuntu-1804-s.html
7) After recovering remote access to your VM, you should resolve you mysql upgrade package bug. You can see better details just trying to do another apt-get upgrade, as now your are already at ubuntu 20.04.
8) In our case, we had to just comment out sql-mode and expire-log-days to not crash mysql upgrade script.
9) Just do another apt-get upgrade, and mysql should be upgraded to version 8.0 without errors.
10) Some other parameters are commented out by upgrade script, prepending an line another comment which says " Deprecated parameter option disabled by maintainer script".
11) Tune your mysqld.cnf again now using docs from new 8.0 version.

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: mysql-server-8.0 8.0.21-0ubuntu0.20.04.4
ProcVersionSignature: Ubuntu 5.4.0-1026.26~18.04.1-azure 5.4.60
Uname: Linux 5.4.0-1026-azure x86_64
ApportVersion: 2.20.11-0ubuntu27.9
Architecture: amd64
CasperMD5CheckResult: skip
Date: Thu Oct 8 04:02:49 2020
ErrorMessage: installed mysql-server-8.0 package post-installation script subprocess returned error exit status 1
Logs.var.log.daemon.log:

MySQLConf.etc.mysql.conf.d.mysql.cnf: [mysql]
MySQLConf.etc.mysql.conf.d.mysqldump.cnf:
 [mysqldump]
 quick
 quote-names
 max_allowed_packet = 16M
MySQLConf.etc.mysql.mysql.conf.d.mysqld_safe_syslog.cnf:
 [mysqld_safe]
 syslog
MySQLVarLibDirListing: ['mysql']
ProcCmdline: BOOT_IMAGE=/boot/vmlinuz-5.4.0-1026-azure root=UUID=a7d32b66-22f6-47a8-bfc7-fa22570bc0c3 ro console=tty1 console=ttyS0 earlyprintk=ttyS0 rootdelay=300
Python3Details: /usr/bin/python3.8, Python 3.8.5, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.18, python-is-python2, 2.7.17-4
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.2ubuntu0.1
SourcePackage: mysql-8.0
Title: package mysql-server-8.0 8.0.21-0ubuntu0.20.04.4 failed to install/upgrade: installed mysql-server-8.0 package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to focal on 2020-10-08 (0 days ago)
modified.conffile..etc.mysql.mysql.conf.d.mysqld.cnf: [modified]
mtime.conffile..etc.mysql.mysql.conf.d.mysqld.cnf: 2020-10-08T04:02:49.412587

[Eduardo Bonato (ebonato)]

This bug is related to bug #1612517

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.