Re: [TUHS] Abstractions

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.