On Thursday 13 February 2003 10:03, Tom Lane wrote:
> mlw <[EMAIL PROTECTED]> writes:
> > Here is the test, configure a server, with sendmail, named, apache, and
> > PostgreSQL. Tell me which of these systems doesn't configure right.

> AFAIK, only one of those four is designed to support multiple instances
> running on a single machine.  This is not unrelated.

One can run many nameds on a single machine by specifying '-c 
alternate_named.conf' , which then points to a different set of zone files, 
listens to either a different port or address, etc.  I have personally done 
this, and it worked as if it were designed to do so.

Apache can easily have multiple instances by passing the location of 
httpd.conf on the command line.  Everything else comes from that. Although 
Apache's virtual hosting is typically use instead, it may be necessary for 
large sites to run multiple instances with degrees of separation at the 
config file level.

I use AOLserver, which in version 3 is designed from the ground up for many 
(even thousands) of instances on a single box.  You access this capability 
with the '-t' switch (it stands for 'tcl config script' -- previous versions 
of AOLserver had an 'ini' file accessed with '-i', and version 3 added the 
tcl config script and deprecated the ini file).  In fact, since there is no 
default, you MUST use -t.  The tcl config script specifies all the parameters 
that instance needs (with the exception of the user and group ID the server 
should run as, if started as root (for port 80 access) -- but that doesn't 
effect PostgreSQL since our port is above 1024).  Two instances can even 
share a tcl config script, as long as the virtual server name is specified on 
the command line, and the tcl config has multiple virtual server sections.  

I personally only lightly use this feature, running a mere half dozen 
AOLserver's on one of my production servers.  All of which share a single 
PostgreSQL instance; but that's a different story.  

AOLserver is an excellent example here, as everything that has a location is 
configurable.  During ./configure, you can specify the prefix and the other 
standard autoconf type options.  This includes the location of the 
--enable-thread built Tcl 8.4 that you have to have first.  I have two 
versions of AOLserver on that machine, and they coexist very well, because I 
_can_ be so specific in where everything lies.  I run OpenACS on two of those 
instances, and, due to the size of that install I have those two pageroots on 
a separate filesystem from the binaries and config script.  It was just a 
single tcl config entry.  No biggie.

Even sendmail has a -c switch to specify the location of sendmail.cf: so, yes, 
you can run multiple instances, although it could be argued that it wasn't 
designed in.

Lamar Owen
WGCR Internet Radio
1 Peter 4:11

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