UsrMove feature (was Re: FESCo meeting minutes for 2011-10-24)

[Harald Hoyer]

On 10/24/2011 08:27 PM, Miloslav Trmač wrote:
> 2011/10/24 Michał Piotrowski<mkkp4x4 at gmail.com>:
>> Hi,
>>
>> 2011/10/24 Chris Adams<cmadams at hiwaay.net>:
>>>>    * Discussion about https://fedoraproject.org/wiki/Features/UsrMove
>>>>      (t8m, 17:26:45)
>>>
>>
>> Cool idea. Next I suggest to stop using
>> /bin
>> /sbin
>> /lib
>> /lib64
>> in F19, and not to create these links on freshly installed systems in F20.
>
> What about
> * the FHS?
> * "#! /bin/sh" in thousands of existing scripts?
>
> If anything, wouldn't it make more sense to move stuff in the opposite
> direction, from /usr/bin to /bin ?  "usr" doesn't really mean anything
> - originally it was used because the filesystem format couldn't
> support more than 64MB(?) in a single volume, so the system had to be
> split to / and /usr.

You want your OS in one directory and not split in 4 toplevel directories.

>
> Also, Fedora already sort-of has a system for stateless OS images -
> see /etc/sysconfig/readonly-root.  What will happen to it?

It does not go away with this feature.

>
> And more importantly, what is the overall benefit to our users?  I
> can't find anything compelling in the "Benefit to Fedora" section (if
> /usr/ can be snapshotted, why not / ?); AFAICT this requires changing
> 257 packages for mostly aesthetic reasons.
>     Mirek

It's not only an aesthetic issue. This enables possibilities, which were 
not doable before.
- snapshot /usr (with btrfs)
- hot swap the OS (/usr) with another version
- mount /usr ro and keep the rootfs writeable
- share the _whole_ OS with other machines