CentOS 8.x Zimbra upgrade

Patch upgrade

For minor version upgrade or patch upgrades we can use:

We can check existing version including patch version via:
```
zmcontrol -v
```
Then check if a updated version or updated patch is available for the same Zimbra major/minor release.
Take backup of VM through snapshot etc. if possible. Other option is to take backup of entire /opt/zimbra folder.
Take copy of /opt/zimbra/conf at another location for quick reference after upgrade
Stop Zimbra as zimbra user
```
zmcontrol stop
```
Update packages as root user
```
yum -y update
```
Compare old copy of /opt/zimbra/conf with new copy for any manual changes that might have got overwritten during upgrade.
Start zimbra again
```
zmcontrol start
```

For major version upgrade:

Download the updated version of zimbra in .tgz (Zip) format
We must keep both old and new zimbra setups with us for future recovery / restore operations
Extract the files of updated version
Take copy of /opt/zimbra/conf at another location for quick reference after upgrade
Go through installation of zimbra using "./install.sh" with required platform override, if required
The installer will automatically detect existing version and go through the update process.
Compare old copy of /opt/zimbra/conf with new copy for any manual changes that might have got overwritten during upgrade.

Following things have been noticed to get affected due to upgrade, which must be fixed promptly:

Spamassasin configuration and scores might get overwritten: CentOS 8.x Zimbra Configure spamassasin email score based on client RBL
CBpolicyd security configuration via http might get overwritten: CentOS 7.x Configure cbpolicyd for Zimbra 8.7
Postfix configuration for copying of incoming/outgoing emails get overwritten: CentOS 8.x Zimbra forward a copy of all incoming and outgoing emails to audit email ID

Refer: