SELinux (Security-Enhanced Linux) is a security module integrated into the Linux system that provides a system administrator an ability to have more control over the system access, security policies, including MAC (Mandatory Access Control). It limits or restricts programs, and cron jobs ability to access files, what actions they can perform by defining a security policy.
One of the basic things a Linux user should know for troubleshooting issues is what version or release of Linux OS is currently on the device. Several issues that you may encounter related to bugs or dependencies related problems may depend on an OS version or kernel version.
Redmine is an open-source free to use web-based tool for project management and issue tracking. Built on top of the Ruby on Rails framework, it offers a cross-platform and cross-database solution that comes with support for multiple projects, wikis, forums, calendars, email notification, and much more.
Sonatype Nexus is a popular repository manager used worldwide for all of most of components, binaries, and build artifacts. It comes with support for the Java Virtual Machine (JVM) ecosystem, including Gradle, Ant, Maven, and Ivy.