Lightup Network Solutions GmbH & Co. KG: Senior Linux & VoIP Infrastructure Engineer – 100% Remote – 4h / day

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Senior Linux & VoIP Infrastructure Engineer

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

About Us

We are a European telecom company with roots as an ISP dating back to 1998. Since 2011, our business has been focused almost entirely on VoIP services, including call origination, termination, and global DID (virtual telephone numbers) services.

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

Our small technical team is building new web-based telecom services, and we’re looking for a hands-on engineer to take full ownership of the infrastructure and 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, responsible for maintaining stability while gradually modernizing and improving the platform. This is a self-directed role suited for someone comfortable working independently and making practical technical decisions.

Your responsibilities will include:

Full responsibility for Linux servers and virtual machines
Planning and executing migration from legacy systems
Operating 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

~26 physical servers, ~40 VMs
Additional VMs at external providers
Locations: Frankfurt (primary), two sites in Switzerland
Mix of CentOS 6/7 (majority), 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 Linux system administration experience
Ability to work independently and take ownership of systems
Experience with virtualization and VM management
Solid troubleshooting skills
Perfect understanding of TCP/IP fundamentals
Knowledge of SIP and RTP, or the ability to learn these protocols quickly
Basic networking knowledge
Excellent shell scripting (bash) and/or Python skills
Ability to automate routine system administration tasks
Fluent English (written and spoken) for daily team 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 FreeBSD familiarity
Additional programming experience (any language)

Required Working Style & Tools

This is a hands-on, console-driven sysadmin role. Our environment is almost entirely command-line based, built on Linux and open-source telecom software.

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

If you do not use most of the following commands and tools on a regular basis, this role is probably not a good fit:

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