Old Zabbix Proxy 4.2 installation could be quite confusing as you cannot grab the latest one to work with old Zabbix server. Fortunately there is archive packages repository at repo.zabbix.com/zabbix/4.2/ubuntu/pool/main/z/zabbix/. You need to keep track which operating systemu should be used. Refer to server requirements as it will be the same. So it’s Ubuntu 14, 16 or 18. First you should grab repository package which can be found named zabbix-release. For example:

zabbix-release_4.2-2+bionic_all.deb

After installation with dpkg command, you can install particular proxy package with either MySQL, PostgreSQL or SQLite3.

zabbix-proxy-mysql_4.2.1-1%2Bbionic_amd64.deb

If you choose MySQL then you need to manually install database package:

sudo apt-get install mysql-server

Then:

service mysql start
service mysql status
mysql
create database zabbix_proxy;
create user zabbix@localhost identified by 'yourpassword';
grant all privileges on zabbix_proxy.* to zabbix@localhost;
quite;

Now you are good to go with loading structure and data into the database:

zcat /usr/share/doc/zabbix-sql-scripts/mysql/server.sql.gz | mysql -uzabbix -p zabbix_proxy

It could take few minutes to complete. Now it’s time to set configuration parameters in /etc/zabbix/zabbix_proxy.conf file:

DBName=zabbix_proxy
DBUser=zabbix
DBPassword=yourpassword

Should something went wrong, check in logs at /var/log/zabbix/zabbix_proxy.log