On Nov 19, 2015, at 3:49 PM, Devin Reade <gdr at gno.org> wrote: > > size of the disk was never the original motivation for > keeping / separate, at least within my memory Prior to SysV, the location of user home directories was not standardized, and AT&T recommended that you put them in /usr.[1] Also, in the PDP days, you had things like the RL and RK series drives, which started at 2.5 MB. If you were well-heeled, you might have several of these, getting you up into the tens of megs. Thus, it made sense to put one major filesystem on each disk, like /, /usr, and /var for a 3-drive system. > it was to minimize the > amount of disk space that needed to be fsck'd before bringing the system > to single user mode That may have been a happy side benefit, but I’ve never read such a thing in a quarter century of using Unix. Reference? > Even in the days of > SunOS 3 (that's SunOS, not Solaris) I was installing the entire OS on > one physical drive, partitioned. Unix goes back about 15 years before the advent of the Sun-3. Being fairly high-end boxes of the time, they likely would have had HDDs in the hundreds of megs range, possibly even the single-digit gigs, plenty for a complete 4.2BSD install. This was also the time in computing history where diskless or small-disk workstations were common, which gives another reason to make /usr separate: get an NFS stack up via RARP or the small local system drive, then attach to a server’s disk to complete the boot process. > The main message is that while CentOS 6 and before *could* have > / and /usr on different filesystems, don't do it with CentOS 7 > per <https://access.redhat.com/solutions/53005> (paywalled). I don’t need to pierce the paywall to know it’s a bad idea. This is enough of a clue: $ ls -l /bin lrwxrwxrwx. 1 root root 7 Jul 7 2014 /bin -> usr/bin [1]: See page 4-8 in the SVR3.2 sysadmin’s guide: http://goo.gl/E9quko