[TUHS] Abstractions

[Nelson H. F. Beebe]

The recent discussions on the TUHS list of whether /bin and /usr/bin
are different, or symlinked, brought to mind the limited disk and tape
sizes of the 1970s and 1980s.  Especially the lower-cost tape
technologies had issues with correct recognition of an end-of-tape
condition, making it hard to span a dump across tape volumes, and
strongly suggesting that directory tree sizes be limited to what could
fit on a single tape.

I made an experiment today across a broad range of operating systems
(many with multiple versions in our test farm), and produced these two
tables, where version numbers are included only if the O/S changed
practices:

------------------------------------------------------------------------
Systems with /bin a symlink to /usr/bin (or both to yet another common
directory) [42 major variants]:

	ArchLinux		Kali			RedHat 8
	Arco			Kubuntu 19, 20		Q4OS
	Bitrig			Lite			ScientificLinux 7
	CentOS 7, 8		Lubuntu 19		Septor
	ClearLinux		Mabox			Solaris 10, 11
	Debian 10, 11		Magiea			Solydk
	Deepin			Manjaro			Sparky
	DilOS			Mint 20			Springdale
	Dyson			MXLinux 19		Ubuntu 19, 20, 21
	Fedora			Neptune			UCS
	Gnuinos			Netrunner		Ultimate
	Gobolinux		Oracle Linux		Unleashed
	Hefftor			Parrot 4.7		Void
	IRIX			PureOS			Xubuntu 19, 20

------------------------------------------------------------------------
Systems with separate /bin and /usr/bin [60 major variants]:

	Alpine			Hipster			OS108
	AltLinux		KaOS			Ovios
	Antix			KFreeBSD		PacBSD
	Bitrig			Kubuntu 18		Parrot 4.5
	Bodhi			LibertyBSD		PCBSD
	CentOS 5, 6		LMDE			PCLinuxOS
	ClonOS			Lubuntu 17		Peppermint
	Debian 7--10		LXLE			Salix
	DesktopBSD		macOS			ScientificLinux 6
	Devuan			MidnightBSD		SlackEX
	DragonFlyBSD		Mint 18--20		Slackware
	ElementaryOS		MirBSD			Solus
	FreeBSD 9--13		MXLinux 17, 18		T2
	FuryBSD			NetBSD 6-1010		Trident
	Gecko			NomadBSD		Trisquel
	Gentoo			OmniOS			TrueOS
	GhostBSD		OmniTribblix		Ubuntu 14--18
	GNU/Hurd		OpenBSD			Xubuntu 18
	HardenedBSD		OpenMandriva		Zenwalk
	Helium			openSUSE		Zorinos
	
------------------------------------------------------------------------

Some names appear in both tables, indicating a transition from
separate directories to symlinked directories in more recent O/S
releases.

Many of these system names are spelled in mixed lettercase, and if
I've botched some of them, I extend my apologies to their authors.

Some of those systems run on multiple CPU architectures, and our test
farm exploits that; however, I found no instance of the CPU type
changing the separation or symbolic linking of /bin and /usr/bin.

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- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- University of Utah                    FAX: +1 801 581 4148                  -
- Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
- 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
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