==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.3.1
- Deployed with iRedMail Easy or the downloadable installer? No
- Linux/BSD distribution name and version:  Ubuntu 16.04.7
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):  MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====
Hello, iRedMail team,

Following the recommendations of the iRedMail team I decided to upgrade my instance to the current version.  I went step by step from 0.9.8 to 1.3.1 where I got stuck since I can’t upgrade iRedAPD from 3.6 to 4.0 because this upgrade requires that I upgrade my Ubuntu 16.04.7 to the next version, so in my case it would be 18.04.

My problem is that when I upgrade the OS to 18.04.6 my SoGo gets completely destroyed.  I already have the repo modified to target version 5 and SoGo is already upgraded and working fine.  Before the OS upgrade the following message is displayed ‘Some third party entries in your sources.list were disabled.  You can re-enable them after the upgrade with the ‘software-properties’ tool or your packages manager.’
When the OS upgrade completes opening the Sogo URL returns error 502 (Bad Gateway) and then digging through the file system I see that half of the files are missing and all symlinks are gone.
Roundcube gets broken also but I can fix it by copying the old www.conf file from the /etc/php/7.0/fpm/pool.d folder to the newer fpm folder.

Checking the status of SoGo service returns:

sogo.service - LSB: SOGo server
   Loaded: loaded (/etc/init.d/sogo; generated)
   Active: failed (Result: exit-code) since Mon 2021-09-27 19:15:21 +06; 3min 32s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 1480 ExecStart=/etc/init.d/sogo start (code=exited, status=1/FAILURE)

Sep 27 19:15:21 mail systemd[1]: Starting LSB: SOGo server...
Sep 27 19:15:21 mail sogo[1480]:  * /usr/sbin/sogod is not executable.
Sep 27 19:15:21 mail systemd[1]: sogo.service: Control process exited, code=exited status=1
Sep 27 19:15:21 mail systemd[1]: sogo.service: Failed with result 'exit-code'.
Sep 27 19:15:21 mail systemd[1]: Failed to start LSB: SOGo server.

When I check the /usr/sbin  the sogod file is not there.

What should I do to upgrade OS versions while preserving Sogo status?

Thanks