Hire the Best Application Server Specialists
in Serbia

Skilled System Administrator and Network Engineer with over 20 years of hands-on experience, adept at organizing networks for single-office environments or multiple offices connected via VPN. I am highly proficient in Unix system administration (Linux and FreeBSD), covering DNS, DHCP, LAMP/LEMP, FTP, SMTP, SNMP, ACLs, firewalls, and NAT, BGP. My expertise also extends to major cloud platforms (AWS, Vultr, DigitalOcean) and virtualization technologies (vSphere, Hyper-V, Proxmox), as well as monitoring tools (Zabbix) and VoIP/IP telephony systems (Asterisk, FreePBX). Here is what past clients have said about my work: - “Pavel was fantastic! My project hit a snag and I needed an FTP server configured quickly. He jumped in immediately, resolved the issue in no time, and answered all my questions in a friendly manner. This guy is a real problem solver!” - “Very smart when it comes to Linux systems—was able to help with our issue.” - “A very skilled and professional expert who solved all additional and unexpected problems with patience. He overdelivered, and I highly recommend working with him!” - “The problem was solved quickly and efficiently.” - “Pavel did a great job tracing the problem and solving it.” - “Pleasure to work with.” I take pride in my ability to quickly diagnose issues, implement reliable solutions, and consistently exceed client expectations.

More than 20 years of working experience in networking and server administration. Administering and scripting networking applications, database applications, web applications and internet & intranet servers In position of expert engineer for networking infrastructure, IT security expert and senior linux/windows/OSX administrator In charge of designing of LAN/MAN/WAN networking infrastructure, designing and implementation of fiberoptic backbone and copper networking installation. Administration of linux servers and networking devices (switches, routers, firewalls, NAS) am in charge of more than 150 linux servers, both physical and virtual Working with L2/L3 switches, routers, firewalls, NAS devices, switching&routing protocols (RIP, OSPF, SNMP, IGRP/EIGRP, VTP, BGP). Certified Cisco and Mikrotik networking engineer. OS platforms - Red Hat/Centos, Debian/Ubuntu, Gentoo, OpenSolaris, BSD flavors, Windows, OSX Server. Networking equipment - Cisco, HP, Mikrotik, ZTE, Huawei Some of the open-source technologies and daemons I have experience with: - bash, perl and python scripting - apache/nginx web servers (standalone, or in backend mode for tomcat, with one or many virtual hosts) - mysql/postgresql database installation and administration - squid (with or without dansguardian+clamav as content filter/realtime AV) - cloud (openstack, AWS, Azure, gcloud, OVH, rackspace, digital ocean....) - snort (with BASE and Snorby as web GUI) and suricata IDS - iptables (with or without web GUI) - BIND (standalone or master/slave) - postfix (as MTA, combined with alot of different tools such as spamassassin, amavis, clamav, roundcube, postfixadmin, dovecot, cluebringer, mailgraph) - zenoss, zabbix and cacti (with plugins and OUIs) - dovecot (as pop3/imap server of choice, combined with postfix and amavis, clamav, roundcube, postfixadmin, spamassassin) - amavis (with alot of customized settings for things such as double AV scanning, DKIM support, catching of spam headers...) - spamassassin (standard and heuristic bayesian analysis, fine tuning of scoring, OCR integration, SPF integration....) - ClamAV (using both standard and unofficial virus definitions, making of 0-day virus signatures caught in the wild...) - freeradius (with MySQL backend for AAA) - samba (in all possible variatons - standalone simple CIFS sharing, member of windows AD, standalone AD controller, one of the controllers in windows AD) - pureftpd, vsftpd and proftpd (as standalone servers or with virtual users) - xen, vmware, hyperv and kvm virtualization (stock or Xenserver/Proxmox distributions) - asterisk (via Elastix linux distribution) - roundcube as preferred web-mail interface (with alot of customized plugins) - openmediavault/openfiler linux distros for NAS - HA clustering (failover based on DRBD and heartbeat/pacemaker+corosync) - NUT (daemon for UPS monitoring and controlling) - openvpn (with various configurations and backends) - pptp vpns (with various configs and backends) - all kind of linux distributions - RH, CentOS, openSuSe, Debian, Ubuntu, Gentoo, Arch.... - hardening of linux distributions (iptables, fail2bain, allow/deny mechanism, AIDE, SELinux, AppArmour, occasional pen testing) - puppet automation - rancid (centralized backup of config files) - bacula, urbackup and rsync backup

My name is Djordje(George) Colic. I live in Serbia. I am windows and linux server system administrator. I have MCSA certificate. For 8 years I was working as system administrator for Mcs systems from San Diego and Miami Lakes IT . This is remote job. I heave experience in using ConnectWise and Ninja RMM as remote management tools. I am logging in to remote networks via ConnectWise or VPN- L2TP/IPsec or OpenVPN and then I use RDP to login to server or any workstation. I am giving support to customers via phone, ConnectWise , RDP or TeamViewer. This support includes their servers, workstations, printers , support with their dedicated applications , office 365. I am giving suport to VOIP customers. They have AT&T Synpase or SkyTalk phone system. Synapse Gateways are PSTN 67010 or SIP 67070. Routers: I was working with SonicWall , Peplink , Mikrotik routers . I am in charge for the maintenance of customer’s and office servers and workstations . For automation tasks I am using batch and powershell scripts. Server OS: Windows Server 2016 or 2012. Workstations: windows 10 or 7. Linux server OS: Red Hat . I am logging in to linux servers via SSH to do every day management tasks. Virtualization: VMWare , HyperV. Cloud: I have experience working in AWS . Every network is Domain network with Domain Controller. For file server we are using Synology NAS where important documents are kept on network share. I am also using NAS as VPN server to access remote network. I have knowledge of Java programming and power shell. As DevOPS engineer , I was working for Avi . Our client had Ping Directory , Ping Proxy servers . There were different environments. Server OS: Red Hat Enterprise Linux Server release 7.9 . I was logging into client network via SSH. I have experience in managing linux servers.