The post-installation script for the zabbix-agent2 Debian package (introduced by ZBX-28169 to fix world-readable config files) performs chown on plugin config files under /etc/zabbix/zabbix_agent2.d/plugins.d/ without verifying their existence.

Steps to reproduce:

1. Install zabbix-agent2 (any version < 7.0.32)
2. Delete one or more conffiles from /etc/zabbix/zabbix_agent2.d/plugins.d/ (e.g., rm /etc/zabbix/zabbix_agent2.d/plugins.d/smart.conf)
3. Upgrade to zabbix-agent2 7.0.32 with apt-get install o DPkg::Options::=-force-confold zabbix-agent2

Result:

The postinst script fails with exit status 1, leaving the package unconfigured.

Setting up zabbix-agent2 (1:7.0.32-1+ubuntu20.04) ...
chown: cannot access '/etc/zabbix/zabbix_agent2.d/plugins.d/smart.conf': No such file or directory
dpkg: error processing package zabbix-agent2 (--configure):
 installed zabbix-agent2 package post-installation script subprocess returned error exit status 1

This leaves the package in a "not fully installed or removed" state, blocking all subsequent package operations

Expected:

The postinst script should gracefully handle missing conffiles (e.g., using chown -f or checking file existence before chown).

Workaround:

Reinstall with --force-confmiss to restore deleted conffiles:

apt-get install --reinstall -o DPkg::Options::=--force-confold -o DPkg::Options::=--force-confmiss zabbix-agent2

Suggested fix:

Use chown -f or guard the chown with a file existence check, e.g.:

[ -f "$file" ] && chown zabbix:zabbix "$file"