Looking at:

https://en.wikipedia.org/wiki/Unix_filesystem#Conventional_directory_layout

and

https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard

and also `man hier`.
It seems pretty clear that it should contain the binaries to make the
system bootable. That is coherent with the purpose of the first level of
the filesystem hierarchy. On /usr it is expected to have software that
is not strictly required to boot and it can be on a mounted directory,
long time ago, I used to mount /usr on NFS on some systems.
It is true that you can always play with /opt and /usr/local, but the
only reason I see to fill the first level is that now the "minimal
bootable" function is satisfied by the initrd. So you don't need anymore
2 levels like slash root and /usr, at the same time, I see that this
decision is impacting solutions that do not use initrd, and also oblige
the sysadmin to plan bigger partitions for "/".

4-5 years ago I had an issue with a mostly-opensource software that was
installing on /usr/xxx subdirectory and needed a max of 200G of space if
you wanted to install it full. When I was trying to mount /usr/xxx to a
separate partition, I discovered the link "/usr -> /". My bad, I did not
keep myself updated.

But also I didn't find it a very solid solution, with my ignorance on
this topic I almost fucked up the filesystem. I actually think that is
not a solution at all, it's just a ack to solve in a fast way a problem
that should be faced at packaging level. I find that acceptable if done
by a sysadmin, but if done by a distribution, it's just laziness.


Il 14/12/22 13:22, Hendrik Boom ha scritto:
> On Wed, Dec 14, 2022 at 03:35:39AM -0600, hal wrote:
>>
>>
>> On 12/13/22 16:59, Harald Arnesen via Dng wrote:
>>> Steve Litt [13/12/2022 16.28]:
>>>
>>>> I meant statically linked. If you can only open your root partition at
>>>> the start, executables can't depend on loadable libraries. I'm pretty
>>>> sure that "sbin" originally stood for "static binaries".
>>>
>>> No. Dynamically linked binaries came much later (SunOS?) than /sbin.
>>>
>>
>> Just to muddy the water here, back in the mid '90s a Solaris admin told me /sbin was for "system binaries". Not sure if that was by his own definition or not.
>
> That's certainly what I always considered it to mean.
>
> -- hendrik
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