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<h1>Controlling Multiple UPSes on one Machine</h1>
<h2>General</h2>
You may want to use your server to control multiple UPSes.
With <b>apcupsd</b> version 3.8.3 or later, this is possible
by proper configuration and by running one copy of <b>apcupsd</b>
for each UPS to be controlled.
<p></p>A multiple UPS configuration might be configured like
the following diagram:
<pre>
Multi-UPS Configuration (apcupsd 3.8.3 only)
--------------------- serial port ------
| | <============> | |
| Computer A running | Power | UPS |
| two copies of | <============= | 1 |
| apcupsd | ------
| | serial port ------
| | <============> | |
--------------------- | UPS |
| ==== | 2 |
| Ethernet || ------
| ||
--------------------- ||
| | ||
| Computer B running | ||
| apcupsd in | Power ||
| slave mode | <===========
| |
| |
---------------------
</pre>
<h2>Configuration</h2>
The way to accomplish the above is to ensure that none of the
critical files used by each of the two copies of <b>apcupsd</b>
are the same. By using suitable configuration options, this is
possible.
<h3>The First Copy of Apcupsd</h3>
For example, assuming you have SmartUPSes in both cases,
to configure and install the first
copy of <b>apcupsd</b>, which controls a UPS and Computer A,
one could use the following configuration:
<pre>
./configure \
--prefix=/usr \
--sbindir=/sbin \
--with-cgi-bin=/home/http/cgi-bin \
--enable-cgi \
--with-css-dir=/home/http/css \
--with-log-dir=/etc/apcupsd \
--with-serial-dev=/dev/ttyS0 \
--enable-pthreads \
--with-nis-port=7000 \
--enable-powerflute
</pre>
This is pretty much a "normal" installation using many of the
defaults. Once built and installed, this would control the first UPS
and cause a shutdown of the system when the batteries are low.
This copy of <b>apcupsd</b> will be started and stopped automatically
when the system is booted and halted.
<h3>The Second Copy of Apcupsd</h3>
To configure and install the second copy
of <b>apcupsd</b>, which controls the second UPS and Computer
B, you could use the following configuration:
<pre>
./configure \
--prefix=$HOME/apcupsd/bin \
--sbindir=$HOME/apcupsd/bin \
--enable-cgi \
--with-cgi-bin=$HOME/apcupsd/bin \
--with-log-dir=$HOME/apcupsd/bin \
--with-pid-dir=$HOME/apcupsd/bin \
--sysconfdir=$HOME/apcupsd/bin \
--with-lock-dir=$HOME/apcupsd/bin \
--with-pwrfail-dir=$HOME/apcupsd/bin \
--with-serial-dev=/dev/ttyS1 \
--enable-pthreads \
--with-nis-port=7001 \
--disable-install-distdir
</pre>
Note, in this case, we use considerably more configuration options
to ensure that the system files are placed in a different
directory ($HOME/apcupsd/bin). We have also selected a different
serial port and a different NIS (Network Information Server) port.
And finally, we have used the <b>--disable-install-distdir</b> option,
which prevents <b>make install</b> from doing the final system installation
(i.e. the modification of the halt script) since this was previously
done.
<h3>Important Steps after Installation of the Second Copy</h3>
After the <b>make install</b> of the second copy of
<b>apcupsd</b> there are a number important steps
to complete. You must either remove or modify the file
<b>$HOME/apcupsd/bin/apccontrol</b>, so that it will not
shutdown Computer A when the battery of UPS 2 is low. One
suggestion is to copy <b>examples/safe.apccontrol</b> into
<b>$HOME/apcupsd/bin/apccontrol</b>. Alternatively, you could
edit the <b>$HOME/apcupsd/bin/apccontrol</b> and delete all
statements that attempt to shutdown the machine.
<p></p>Another important step is to find a way to shutdown
Computer B when UPS 2's battery is low. Probably the simplest
way to do this is to edit <b>$HOME/apcupsd/bin/apcupsd.conf</b>
on Computer A so that this second copy of <b>apcupsd</b> becomes
a network master. Then install a standard slave configuration on
Computer B.
<p></p>Please remember that if UPS 1's batteries are exhausted
before UPS 2's batteries, Computer B may not be properly shutdown.
And at the current time, there is no simple means to make the two
copies of <b>apcupsd</b> running on Computer A communicate.
Thus there are certain risks in such a configuration.
However, these configurations can be very useful for powering electronic
equipment and such.
<p>If Computer B is vitally important, it would probably be better
to purchase a serial port card for it, or perhaps use a USB UPS.
To ensure that it is properly shutdown if Computer A goes down,
you could run a second copy of <b>apcupsd</b>
on Computer B as a slave connected to the main copy of <b>apcupsd</b>
on Computer A. Thus Computer B would be running two slaves, one
driven by the master controlling UPS 1 and the other by the master
controlling UPS 2, and Computer B could be shutdown by the first
master that signaled it to do so.
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