A CentOS Linux developer works on the CentOS Linux distribution, which is a free, open-source platform derived from the sources of Red Hat Enterprise Linux (RHEL). Their duties include developing, testing, and maintaining the CentOS operating system, troubleshooting issues, and providing fixes and updates. They collaborate with other developers and the user community to enhance the system's performance, security, and functionality. They also document their work for reference and assist users with technical problems. They need strong programming skills, particularly in languages like Python or Perl, and a deep understanding of Linux systems.