Title: Reuse of OpenBSD packages for trying runtime

	Title: Reuse of OpenBSD packages for trying runtime
	Author: Solène
	Date: 19 September 2021
	Tags: openbsd unix
	Description:

	# Introduction

	So, I'm currently playing with OpenBSD trying each end user package
	(providing binaries) and see if they work when installed alone. I
	needed a simple way to keep packages downloaded and I didn't want to go
	the hard way by using rsync on a package mirror because it would waste
	too much bandwidth and would take too much time.

	The most efficient way I found rely on a cache and ordering the source
	of packages.

	# pkg_add mastery

	pkg_add has a special variable named PKG_CACHE that when it's set,
	downloaded packages are copied in this directory. This is handy
	because every time I will install a package, all the packages
	downloaded by will kept in that directory.

	The other variable that interests us for the job is PKG_PATH because we
	want pkg_add to first look up in $PKG_CACHE and if not found, in the
	usual mirror.

	I've set this in my /root/.profile

	```shell file
	export PKG_CACHE=/home/packages/
	export PKG_PATH=${PKG_CACHE}:http://ftp.fr.openbsd.org/pub/OpenBSD/snapshots/pa…
	```

	Every time pkg_add will have to get a package, it will first look in
	the cache, if not there it will download it in the mirror and then
	store it in the cache.

	# Saving time removing packages

	Because I try packages one by one, installing and removing dependencies
	takes a lot of time (I'm using old hardware for the job). Instead of
	installing a package, deleting it and removing its dependencies, it's
	easier to work with manually installed packages and once done, remove
	dependencies, this way you will keep already installed dependencies
	that will be required for the next package.

	```script shell
	#!/bin/sh

	# prepare the packages passed as parameter as a regex for grep
	KEEP=$(echo $* \| awk '{ gsub(" ","\|",$0); printf("(%s)", $0) }')

	# iterate among the manually installed packages
	# but skip the packages passed as parameter
	for pkg in $(pkg_info -mz \| grep -vE "$KEEP")
	do
	# instead of deleting the package
	# mark it installed automatically
	pkg_add -aa $pkg
	done

	# install the packages given as parameter
	pkg_add $*

	# remove packages not required anymore
	pkg_delete -a
	```

	This way, I can use this script (named add.sh) "./add.sh gnome" and
	then reuse it with "./add.sh xfce", the common dependencies between
	gnome and xfce packages won't be removed and reinstalled, they will be
	kept in place.

	# Conclusion

	There are always tricks to make bandwidth and storage more efficient,
	it's not complicated and it's always a good opportunity to understand
	simple mechanisms available in our daily tools.