mrtg for Debian
---------------

  1. IMPORTANT CHANGES
  2. DIRECTORY OF PAGES
  3. HOW TO DISABLE SYSTEMD/INIT.D AUTOSTART
  4. OVERRIDING THE SYSTEMD
  5. TROUBLESHOOTING MRTG
  6. TROUBLESHOOTING: 403 Forbidden

  1. IMPORTANT CHANGES
  --------------------

  The most relevant recent change is the MRTG is running via init/systemd
  (since revision 2.17.8+git20211022.f52e91e-1). Please, read the file
  /usr/share/doc/mrtg/NEWS.Debian.gz to know about these changes.

  The most relevant change is that currently (since revision
  2.17.8+git20211022.f52e91e-1) MRTG is running via init/systemd. The current
  start command called by init/systemd can be viewed below:

    LANG=C /usr/bin/mrtg --daemon --fhs --user=mrtg

  The default configuration file is /etc/mrtg/mrtg.cfg

  2. DIRECTORY OF PAGES
  ---------------------

  The default directory for pages generated from MRTG is /var/www/html/mrtg/.
  This directory needs to be owned by 'mrtg' user and 'www-data' group. This
  configuration will allow MRTG to write the pages and a web server (Apache,
  lighttpd, etc.) reads the content. A good permission for this directory is
  0750.

  3. HOW TO DISABLE SYSTEMD/INIT.D AUTOSTART
  ------------------------------------------

  Maybe you want to disable the autostart to use a cronjob. In Debian, the
  init.d script will call a systemd config file, if available. The MRTG on
  Debian has a systemd config file. To disable the autostart, run the following
  command:

    # systemctl disable mrtg

  To re-enable, run:

    # systemctl enable mrtg

  4. OVERRIDING THE SYSTEMD
  -------------------------

  To change any option in systemd config file, run the following command:

    # systemctl edit mrtg

  To see details about how to change a specific option, read this post[1].

  [1] https://askubuntu.com/questions/659267/how-do-i-override-or-configure-systemd-services

  5. TROUBLESHOOTING MRTG
  -----------------------

  If MRTG not work after your changes:

    - Check the log at /var/log/mrtg/mrtg.log
    - Run '# systemctl status mrtg'
    - Run '# journalctl -xeu mrtg'
    - Verify the permissions for each file and directory. The recommended
      permissions are:

      FILE                 OWNER:GROUP    PERM
      ----------------------------------------
      /etc/mrtg/:           mrtg:mrtg     2750
      /etc/mrtg/*:          mrtg:mrtg     0640
      /var/lib/mrtg/:       mrtg:mrtg     0750
      /var/log/mrtg/:       mrtg:mrtg     0750
      /var/www/html/mrtg/:  mrtg:www-data 0750
      /var/www/html/mrtg/*: mrtg:www-data 0640

    - Stop the service (# systemctl stop mrtg or /etc/init.d/mrtg stop) and run
      MRTG via command line. Example:

        # LANG=C mrtg

      The command above will use the default config file, /etc/mrtg/mrtg.cfg.
      To call other config file, use something like this:

        # LANG=C mrtg ~/test/test.cfg

      Check the on screen messages and the main log at /var/log/mrtg/mrtg.log.

    - When MRTG is not running, a /run/mrtg/mrtg.pid file must not exist.
      Remove it if needed. However, is a bit odd there is a pid file without a
      service running. Please, double check it.

  6. TROUBLESHOOTING: 403 Forbidden
  ---------------------------------

  This is not a MRTG issue. Some web servers block directory listing. In other
  words, if you don't have an index file, like index.html or index.php, you
  won't be able to see the content of the /var/www/html/mrtg/ directly. The
  basic solutions are:

    - Creating an index.html to list each .html generated by MRTG.
    - Calling a .html file created by MRTG. An example:

        http://myserver.example/203.0.113.10_eth0.html

    - Enabling the directory listing only for /var/www/html/mrtg/ in your
      webserver.

 -- Joao Eriberto Mota Filho <eriberto@debian.org>  Sun, 31 Oct 2021 20:55:08 -0300