I chose the Osteotrainer platform to test the Linux administration module with my team of three. The first impression was that the materials are well-structured, and the videos do not exceed 15 minutes, which helps with concentration. I went through the first two modules on securing SSH access and configuring the firewall with iptables. The examples in the virtual lab worked without errors, and the intermediate tests clearly highlighted the team's weak points.
One aspect that pleasantly surprised me was the technical support: I received a response in less than two hours to a question about SELinux permissions. The only inconvenience was that some exercises required basic networking knowledge, which not all colleagues had. However, the recommended supplementary material quickly filled this gap. After the first month, I managed to reduce the time to configure a new server from 90 to 40 minutes.