[TUHS] Understanding the /bin, /sbin, /usr/bin, /usr/sbin Split

Warner Losh imp at BSDIMP.COM
Thu Feb 2 03:35:53 AEST 2012

On Feb 1, 2012, at 4:12 AM, Jose R. Valverde wrote:
> So, beyond the point of filling up a disk (and that's the point for the partition
> system) there was a need to ensure you could separate user data from system data:
> adding user programs or data to a separate space (disk, partition, whatever)
> ensured the system space was not filled and the system would not become unusable.

You had different quotas on different partitions as well...  Something most folks don't get these days: you used to get 5MB from the CS department and be grateful they gave you that much...

There were bugs in the dim, dark past too where if you filled up /, the system would crash.  Having a separate / insulated you from that.

Also, fsck and file systems were a little more fragile in the early days than now, so you wanted to make sure that you minimized the amount of data needed to change before / could be mounted rw.  This boot-strapping process these days (on linux) happens in a ram disk, but historically (and still in many BSDs) happens on the actual drive, so any corruption or filesystem issue would take a while to repair, and once repaired you had to reboot to ensure that the pages that were swapped in read-only that might have been changed behind the scenes by fsck were properly flushed.

None of that was mentioned in the article :)


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