Senior Linux & VoIP Infrastructure Engineer

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

About Us

We are a European telecom company that began as an ISP in 1998. Since 2011, our business has 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 run 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 who will take full ownership of the infrastructure and help drive it forward.

The Role

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

You will be the main technical owner of our systems, ensuring stability while gradually modernizing and improving the platform. This is an independent, self-directed role for someone who is comfortable working on their own and making practical technical decisions.

Your responsibilities will include:

• Full responsibility for Linux servers and virtual machines

• Planning and executing migrations 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

• Approximately 26 physical servers and around 40 VMs

• Additional VMs at 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 Linux systems administration experience

• Ability to work independently and take ownership of systems

• Experience with virtualization and VM management

• Strong troubleshooting skills

• Excellent understanding of TCP/IP fundamentals

• Knowledge of SIP and RTP, or the ability to learn them 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 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 Work Style & Tools

This is a hands-on, console-based sysadmin role. Nearly everything is command-line driven, running on Linux and open-source telecom software.

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

If you do not regularly use most of the tools and commands below, this role is likely 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.

Work Setup

• 100% remote

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

• Freelance/contract role

• Monthly compensation: €1,000

How to Apply

Please send your CV to: jobs@lightupnet.de