How to download and setup rocker
Open terminal and run command
                                            git clone https://github.com/rocker-org/rocker.git
                                        
                                        git clone is used to create a copy or clone of rocker repositories.
                                        You pass git clone a repository URL. it supports a few different network protocols and corresponding URL formats.
Also you may download zip file with rocker https://github.com/rocker-org/rocker/archive/master.zip
Or simply clone rocker with SSH
                                            [email protected]:rocker-org/rocker.git                                    
                                    If you have some problems with rocker
You may open issue on rocker support forum (system) here: https://github.com/rocker-org/rocker/issuesSimilar to rocker repositories
Here you may see rocker alternatives and analogs
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