Software installation opinions needed

[Ken Manheimer]

We've actually implemented a refinement on the 'rc.site' scheme that
walter mentioned in a prior article.  The refinements eliminate
problem with additional points-of-failure that the unadorned scheme
introduces.

As walter mentioned, a hook is inserted at the end of /etc/rc to call
rc.site, which in turn is where any site-specific boot activities are
placed.  (We put it in /etc/rc instead of /etc/rc.local because
rc.local is run in the middle of rc (on Suns, at least) and we want
the rc.site stuff to be done *last* in the boot process.)  A couple of
nifty aliases (rc.site was developed as a cshell script, 'cause that's
what i was more comfortable with at the time) allow you to
conditionalize what hosts are to run or to be excluded from running
specific inits:

alias IfHostIn    echo "\!* | grep -s $hostname ;" 'if ($status == 0) then'
alias IfHostNotIn echo "\!* | grep -s $hostname ;" 'if ($status == 1) then'

The rc.site approach has two general benefits - the standard boot rc
files only need to be changed once (to introduce the hook for rc.site
and maybe eliminate any features or bugs the vendor introduced) and
the custom boot activites are centralized in a single place, which has
proven invaluable for keeping track of what does what as our
installation has grown.

The drawback is that all the clients become dependent on some central
server(s) for the rc.site customizations.  The refinement to fix this
consists of changing the hook to the global rc.site to the following
sort of thing:

	if [ -f /usr/local/site/rc.site ]; then
		cp /usr/local/site/rc.site /etc/rc.site
		chmod 555 /etc/rc.site
	fi
	if [ -f /etc/rc.site ]; then
	  echo -n Site-specific business:
	  /etc/rc.site
	  echo "."
	fi

This way, if the global rc.site file is accessible a local copy is
made.  In any case a local copy, if any exists, is executed.  The
trick is that if the current global copy of the rc.site is not
accessible the last copied version is still run anyway.

In the rare cases where the global copy turns out not to be accessible
the last copied version is almost always going to be at least adequate
if not identical.  For almost any situation this setup is more than
adequate to get the right custom activities done...

If it's not too obnoxious of me to do, i recommend the general rc.site
approach highly.  It's helped enourmously to consolidate our handle on
our site's operations and to ease the job of administering
customizations in general and across OS upgrades.

Yay.

Ken Manheimer			 	Nat'l Inst of Standards and Technology
klm at cme.nist.gov (301)975-3539		(Formerly Nat'l Bureau of Standards)
      Factory Automation Systems Division Unix Systems Support Manager

					I like time.  It's one of my favorites.