+-------------------------------------------------------------------------------
| Running syweb on OpenBSD
+-------------------------------------------------------------------------------

syweb's default install assumes that:
  - web server is chrooted at /var/www
  - rrdtool is installed in the chroot
  - symux rrd files are kept in /var/www/symon/rrds/<host>/*.rrd

Customise /var/www/htdocs/syweb/setup.inc if these assumptions are
incorrect. rrdtool must also be copied into the chroot jail; for this,
see rrdtool's pkg-readme document. No /bin/sh is needed there: this
build opens rrdtool directly, through proc_open with an argument array.

The build carries a series of generic changes, each off in the shipped
setup.inc: a site that changes nothing sees the page it always saw.

  $symon['ui']              the template that renders the page,
                            ui/<name>.inc. `default` is the page as it
                            has always been; `noui` is the graphs alone,
                            which index_noui.php still reaches; `modern`
                            offers the resource type and the host side
                            by side, redraws on change, reloads on a
                            timer, and writes urls that name no script;
                            `live` is modern with the graphs refreshed
                            in place, the page never reloading
  $symon['refresh']         seconds between two reloads, 0 to leave it
                            alone. Read by `modern` only, and never
                            applied under cache_duration
  $symon['graph_densities'] screen densities the graphs are offered at
                            through the srcset of their img. [1], the
                            default, draws one image per graph and emits
                            no srcset. [1, 2] adds a candidate drawn
                            twice the size, which a dense screen picks
                            and shows at nominal size. Three is the
                            ceiling. The zoom is part of the cached
                            definition: a key serves what its content
                            says, whatever the request
  $symon['rrdtool_font']    name the graph font outright rather than
                            leaving it to fontconfig substitution

A site of its own can drop local.css, local.js and local.inc in
/var/www/htdocs/syweb. The first two are loaded when they are there,
after the stylesheet and after the page's own script; the third is read
by tools.inc once setup.inc has run, so it overrides any setting of it.
None of the three is shipped, and none is touched by an update.

local.inc rather than setup.inc for anything a site changes: setup.inc
is installed @sample and stays as it was left, so an update never
carries a new default into a configured site, while tools.inc is
replaced every time.

A busy page is worth a longer $symon['cache_duration'] than the 20
seconds of the sample. Every load of the page expires the definitions of
the window it did not write, and a request for a graph that arrives
after that finds no key left -- reported now as the missing key it is.
