2017
Poettering - systemd for Administrators
    http://0pointer.de/blog/projects/systemd-pdf.html
    https://github.com/shibumi/systemd-for-administrators
    https://raw.githubusercontent.com/shibumi/systemd-for-administrators/master/systemd-handbook.pdf
    https://www.slideshare.net/susantsahani/systemd-for-administrators
    ru
    https://github.com/nnz1024/s4a/
    https://github.com/nnz1024/s4a/releases
    http://www2.kangran.su/~nnz/pub/s4a/
    http://www2.kangran.su/~nnz/pub/s4a/s4a_latest.pdf