Comment 5 for bug 1777008

As-is:
root@b:~# vim /etc/dovecot/conf.d/10-logging.conf
root@b:~# sudo systemctl restart dovecot
root@b:~# sudo mv /var/log/dovecot.log /var/log/dovecot.log.1
root@b:~# sudo doveadm log reopen
root@b:~# ll /var/log/dovecot.log
ls: cannot access '/var/log/dovecot.log': No such file or directory

Upgrade:
# apt install mail-stack-delivery
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
The following additional packages will be installed:
  dovecot-core dovecot-imapd dovecot-managesieved dovecot-pop3d dovecot-sieve
Suggested packages:
  dovecot-gssapi dovecot-ldap dovecot-lmtpd dovecot-mysql dovecot-pgsql dovecot-solr dovecot-sqlite ntp
The following packages will be upgraded:
  dovecot-core dovecot-imapd dovecot-managesieved dovecot-pop3d dovecot-sieve mail-stack-delivery
6 upgraded, 0 newly installed, 0 to remove and 14 not upgraded.
Need to get 3289 kB of archives.
After this operation, 1024 B disk space will be freed.
Do you want to continue? [Y/n] Y
Get:1 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 dovecot-managesieved amd64 1:2.2.33.2-1ubuntu4.1 [41.6 kB]
Get:2 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 dovecot-sieve amd64 1:2.2.33.2-1ubuntu4.1 [311 kB]
Get:3 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 dovecot-pop3d amd64 1:2.2.33.2-1ubuntu4.1 [32.3 kB]
Get:4 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 dovecot-imapd amd64 1:2.2.33.2-1ubuntu4.1 [153 kB]
Get:5 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 dovecot-core amd64 1:2.2.33.2-1ubuntu4.1 [2740 kB]
Get:6 http://archive.ubuntu.com/ubuntu bionic-proposed/main amd64 mail-stack-delivery all 1:2.2.33.2-1ubuntu4.1 [10.4 kB]
Fetched 3289 kB in 1s (2986 kB/s)
(Reading database ... 29440 files and directories currently installed.)
Preparing to unpack .../dovecot-managesieved_1%3a2.2.33.2-1ubuntu4.1_amd64.deb ...
Unpacking dovecot-managesieved (1:2.2.33.2-1ubuntu4.1) over (1:2.2.33.2-1ubuntu4) ...
Preparing to unpack .../dovecot-sieve_1%3a2.2.33.2-1ubuntu4.1_amd64.deb ...
Unpacking dovecot-sieve (1:2.2.33.2-1ubuntu4.1) over (1:2.2.33.2-1ubuntu4) ...
Preparing to unpack .../dovecot-pop3d_1%3a2.2.33.2-1ubuntu4.1_amd64.deb ...
Unpacking dovecot-pop3d (1:2.2.33.2-1ubuntu4.1) over (1:2.2.33.2-1ubuntu4) ...
Preparing to unpack .../dovecot-imapd_1%3a2.2.33.2-1ubuntu4.1_amd64.deb ...
Unpacking dovecot-imapd (1:2.2.33.2-1ubuntu4.1) over (1:2.2.33.2-1ubuntu4) ...
Preparing to unpack .../dovecot-core_1%3a2.2.33.2-1ubuntu4.1_amd64.deb ...
Unpacking dovecot-core (1:2.2.33.2-1ubuntu4.1) over (1:2.2.33.2-1ubuntu4) ...
Setting up dovecot-core (1:2.2.33.2-1ubuntu4.1) ...
(Reading database ... 29440 files and directories currently installed.)
Preparing to unpack .../mail-stack-delivery_1%3a2.2.33.2-1ubuntu4.1_all.deb ...
Unpacking mail-stack-delivery (1:2.2.33.2-1ubuntu4.1) over (1:2.2.33.2-1ubuntu4) ...
Processing triggers for ufw (0.35-5) ...
Processing triggers for ureadahead (0.100.0-20) ...
Setting up dovecot-sieve (1:2.2.33.2-1ubuntu4.1) ...
Setting up dovecot-pop3d (1:2.2.33.2-1ubuntu4.1) ...
Processing triggers for systemd (237-3ubuntu10) ...
Setting up dovecot-imapd (1:2.2.33.2-1ubuntu4.1) ...
Processing triggers for man-db (2.8.3-2) ...
Setting up dovecot-managesieved (1:2.2.33.2-1ubuntu4.1) ...
Setting up mail-stack-delivery (1:2.2.33.2-1ubuntu4.1) ...
Processing triggers for dovecot-core (1:2.2.33.2-1ubuntu4.1) ..

# Issue resolved after restart and log reopen working:
root@b:~# ll /var/log/dovecot.log
-rw------- 1 root root 520 Jun 22 06:17 /var/log/dovecot.log
root@b:~# sudo mv /var/log/dovecot.log /var/log/dovecot.log.2
root@b:~# sudo doveadm log reopen
root@b:~# ll /var/log/dovecot.log
-rw------- 1 root root 0 Jun 22 06:17 /var/log/dovecot.log