When importing data you will probably be extracting or unpacking a tarball File
To unpack or extract a tar file, type:
tar -xvf file.tar
To save disk space and bandwidth files are saved using compression program such as gzip or bzip2. To extract / unpack a .tar.gz (gzip) file, enter (note -z option):
tar -xzvf file.tar.gz
To extract / unpack a .tar.bz2 (bzip2) file, enter (note -j option):
tar -xjvf file.tar.bz2
to extract gzip file
tar xvzf file.tar.gz