To deploy from a tar file, the command depends on your version of tar. With a modern version of tar, you can run the following command:
tar xvzf splunk-7.0.x-xxx-Linux-xxx.tgz
Older versions may not handle gzip files directly, so you may have to run the following command:
gunzip -c splunk-7.0.x-xxx-Linux-xxx.tgz | tar xvf -
This will expand into the current directory. To expand into a specific directory, you can usually add -C, depending on the version of TAR, as follows:
tar -C /opt/ -xvzf splunk-7.0.x-xxx-Linux-xxx.tgz