[9fans] new plan 9 update wrapping

[9fans] new plan 9 update wrapping

[rsc]

As Rob said, there is a new Plan 9 package today
(plan9.bell-labs.com/plan9dist/ureg.html).

This message is a summary of the different types of archives that
wrap(8) creates, and a note on what you need to do to install the new
update.  The short version is that we introduced a new concept into
the wrap tools, and so in order to install the new update you will
need to download new wrap binaries first and write them into
/386/bin/wrap.  These are also on that web page.

The rest of this message explains the wrap process in a bit of
detail, and can be skipped when you start to get bored.

Every time a significant amount of change or a signficant change has
happened in the system, we will put out a new package.  A package is
the full tree, currently about 50MB compressed, 130MB uncompressed.

Between packages, if minor changes happen that don't warrant a new
full package, we may put out partial updates; the updates we have
published to this point were partial updates.  These are always
relative to a base package, and contain only files changed since that
package.  Updates to updates don't happen -- updates are always
relative to the last full package, for a number of reasons described
in wrap(8).

Each time we publish a full package, we will also publish an ``update
package''.  This is a hybrid of the two -- it contains only changed
files, but once installed acts as though you had installed the full
package.  Thus we can chain update packages without you needing to
download the whole system every time a full package comes out.

The web page currently contains today's full package and an update
package relative to the original package from June 7.  Even if you
have downloaded a newer package or you applied some of the updates,
this update package will work for you.

The original wrap tools from June 7 don't parse update packages,
which is why you have to get the new wrap before trying to update
your system.

In case your head is spinning, an example.  The current package
history looks something like

	* June 7 - first full package
	  - June 7 -> June 11 update
	* June 11 - second full package
	  - June 7 -> June 12 update
	  - June 11 -> June 12 update
	* June 12 - third full package
	  + June 7 -> June 17 update package
	* June 17 - fourth full package

Since updates are relative to a base package, if you had installed
a June 7 package and then a June 7 -> June 11 update, you still
had to install the June 7 -> June 12 update when the next package
came out, because updates don't change the date on the base package.

This new ``update package'', however, does exactly that.
It contains all the changes to the entire tree.  Wrap/inst makes
those changes and then stamps your installation as being
equivalent to having the June 17 full package.

Thus from now on we will only publish an update package
relative to the previous package.  If you are multiple packages
out of date, you will have to install those updates in order to
chain your way to the current one.  As Rob mentioned, we
expect that the update frequency will calm down quite a bit
now.

A final comment.  If you change a file after installing a package,
and a new update comes along that has a newer version of that
file, wrap/inst will print a warning but not update it.  The new
update contains extra examples in /mail/lib/smtpd.conf and
/sys/lib/lp/devices, for example; if you've customized these,
you'll get a (harmless) warning that a newer version has been
tossed aside in favor of your own.  You can run the wdiff
command that inst prints out to see what the differences between
the new version and yours are.

Enjoy.

Russ