Interview — Systems Administrator
- Tell me about your professional journey in systems.
I started in N1/N2 support and specialized in Windows Server, Active Directory and Linux system administration. Over time I expanded into virtualization (VMware, Hyper-V) and monitoring with Zabbix and Grafana. I chose each step to learn a new layer of the technology stack.
- A server does not boot and the BIOS shows a POST error. How do you diagnose it?
I interpret the beep codes or diagnostic LEDs. I check the RAM first (I remove modules and test with Memtest86+), then the expansion cards, the power supply and finally the CPU. At the same time, I notify the team and open a ticket to leave traceability.
- How would you configure a Linux server to send logs to a centralized Syslog server?
I edit /etc/rsyslog.conf adding . @@server-ip:514 for TCP. I open port 514 in the firewall, restart rsyslog and validate with the logger command. In production I add TLS and authentication to secure the channel.
- You have VLAN 10 (Users) and VLAN 20 (Servers). How do you communicate them in a controlled manner?
I implement inter-VLAN routing with an L3 switch or router-on-a-stick with 802.1q subinterfaces. I configure a gateway IP for each VLAN and apply ACLs to allow only the necessary protocols (e.g. HTTPS and SSH from users to servers, denying the rest).
- Explain a critical incident of systems that you have managed after hours.
At 2am the mail service went down affecting 400 users. I connected via VPN, detected a full disk on the queue server, freed up space and restarted the service. The service came back in 35 minutes. Then I implemented an alert in Zabbix for 80% disk usage.
- Describe a major infrastructure change that you have implemented with high risk.
I migrated a file server with 2 TB of data to a new NAS in a 4-hour overnight window. I prepared a verified backup, documented rollback plan and communicated to users 48 hours in advance. The migration was completed in 3h 20min without incident.
- Have you ever detected unauthorized access or a vulnerability? How did you handle it?
Analyzing AD logs I detected suspicious access at 3am with a service account. I blocked the account and IP in the firewall, isolated the server and escalated to management. I changed all service account passwords and implemented MFA for all privileged accounts.
- How do you organize technical documentation so that the team can act without you?
I maintain a wiki in Confluence with runbooks for each critical system: startup, shutdown and resolution of the most frequent incidents. The configurations are versioned in Git. When someone new comes in, I do a handover session and review the documentation every quarter.
- What measures do you take to anticipate capacity or performance problems?
I have dashboards in Grafana with alerts at three levels (70%, 85%, 95%) for CPU, RAM, disk and network. Every month I review growth trends to plan capacity. I automate patches by deploying them first in test and, if it is stable for 72 hours, I move to production.