Some docs fixes

Hi there,
while setting up a small Dremio cluster on plain Linux servers I noticed some small things to fix in the docs:

  • At ; point 4) states “Unpack Dremio into /etc/dremio”, it should be “Unpack Dremio into /opt/dremio” as correctly displayed in the example.

  • In the same page, the sample SystemD unit file sets the config directory as --config /opt/dremio/conf, although the user is instructed to copy the configuration to /etc/dremio, so the option should be --config /etc/dremio.

  • The chkconfig should enable Dremio on levels 2345 rather than 3456 (6 is reboot).

  • To have Dremio use the directories created in step 3, it is necessary to specify DREMIO_LOG_DIR=/var/log/dremio and
    DREMIO_PID_DIR=/var/run/dremio in /etc/dremio-env.

Thanks @fabiocorneti! Docs will be shortly updated.