Senior Linux & VoIP Infrastructure Engineer

Remote • Part-time (4 hours/day) • €1,000/month • Freelance

About Us

We are a European telecommunications company that started as an ISP in 1998. Since 2011, we have focused primarily on VoIP services, including call origination, termination, and global DID (virtual phone numbers).

Our infrastructure is fully self-managed and built mainly with open-source software. We operate our own ASN, maintain BGP sessions with upstream providers, and host physical infrastructure in Germany and Switzerland.

Our small technical team is developing new web-based telecom services, and we are looking for a hands-on engineer to take full ownership of the infrastructure and help move it forward.

The Role

This is a hybrid Sysadmin / DevOps / VoIP operations role with full responsibility for our infrastructure.

You will be the primary technical owner of our systems, ensuring stability while steadily modernizing and improving the platform. This is an independent, self-directed position for someone who is comfortable working autonomously and making practical technical decisions.

Your responsibilities will include:

• Full responsibility for Linux servers and virtual machines

• Planning and executing migrations from legacy systems

• Running and improving the VoIP stack (Asterisk, Kamailio)

• Providing infrastructure, tools, and environments for developers

• Testing new VoIP vendors and SIP connections

• Troubleshooting customer and routing issues

• Improving automation, monitoring, backups, and security

• Basic network operations (BGP environment, routers, switches)

Current Environment

Infrastructure

• Approximately 26 physical servers and around 40 VMs

• Additional VMs hosted with external providers

• Locations: Frankfurt (main) and two sites in Switzerland

• Mostly CentOS 6/7, plus Ubuntu and one legacy FreeBSD VM

Core Software

• MySQL, MariaDB, Galera Cluster

• Asterisk, Kamailio

• Apache, HAProxy, Varnish

• BackupPC

• tinydns, dnscache

• Nagios

• Joomla

Hardware & Network

• Supermicro servers (100%) with IPMI (KVM-over-IP)

• QNAP NAS systems

• Juniper M-series routers

• Juniper SRX routers

• HP 41xx switches

• Own ASN with BGP upstreams

Requirements

Must have:

• Strong experience in Linux systems administration

• Ability to work independently and take ownership of systems

• Experience with virtualization and managing VMs

• Strong troubleshooting skills

• Excellent understanding of TCP/IP fundamentals

• Knowledge of SIP and RTP, or the ability to learn them quickly

• Basic networking knowledge

• Strong shell scripting (bash) and/or Python skills

• Ability to automate routine system administration tasks

• Fluent English (written and spoken) for daily communication and video calls

Nice to have:

• VoIP/SIP experience (Asterisk, Kamailio, SBCs, etc.)

• DevOps or automation experience (Ansible, Docker, CI/CD)

• Experience modernizing legacy infrastructures

• Basic familiarity with FreeBSD

• Additional programming experience (any language)

Required Work Style & Tools

This is a hands-on, console-based sysadmin position. Almost everything is driven through the command line, running on Linux and open-source telecom software.

You should be comfortable spending most of your day in terminal sessions, troubleshooting live systems, and editing configuration files directly.

If you do not regularly use many of the tools and commands listed below, this role may not be a good match:

asterisk, awk, cat, cp, cut, df, diff, dig, grep, head, host, htop, ifconfig, iptables, kamctl, last, ls, mail, mailx, mkdir, mtr, mv, mysql, mysqldump, netstat, ping, pssh, pwd, rm, rsync, screen, sed, sngrep, sort, ssh, systemctl, tail, tcpdump, top, traceroute, vi, vim, vimdiff, w, who, whois, yum

This role is best suited for someone with several years of real-world Linux and network operations experience, who is comfortable working independently in production environments.

Work Setup

• Fully remote (100%)

• Part-time: about 4 hours per day (flexible schedule), Monday to Friday

• Freelance/contract position

• Monthly compensation: €1,000

How to Apply

Please send your CV to: jobs@lightupnet.de