Re: [gentoo-dev] usr merge

[Alexis Ballier]

On Wednesday, April 6, 2016 6:15:58 AM CEST, Richard Yao wrote:
>> On Apr 4, 2016, at 9:19 PM, William Hubbs <williamh@g.o> wrote:
>>
>> All,
>>
>> I thought that since the usr merge is coming up again, and since I lost
>> track of the message where it was brought up, I would open a
>> new thread to discuss it. ...
>
> Here are the violations:
>
> http://refspecs.linuxfoundation.org/FHS_3.0/fhs-3.0.html#binEssentialUserCommandBinaries
>
> http://refspecs.linuxfoundation.org/FHS_3.0/fhs-3.0.html#sbinSystemBinaries
>
> http://refspecs.linuxfoundation.org/FHS_3.0/fhs-3.0.html#libEssentialSharedLibrariesAndKern
>

well, those are not violations: fhs mandates a certain set of binaries in 
those paths; this is still the case with a usr-merged system.

i thought the symlinks would be a problem, but fhs states:
> The following directories, or symbolic links to directories, are required in /.

so, really, i dont see any violation there


>> I don't think creating usr merged stages would be that difficult. I
>> think it would just be a matter of creating a new version of baselayout
>> that puts these symlinks in place:
>>
>> /bin->usr/bin
>> /lib->usr/lib ...
>
> We will have users whose system configurations rely on the FHS
> complain about us breaking boot if we force this.


i dont think anybody is talking about forcing this


>> I put some thought also in how to nigrate live systems, and I'm not sure
>> what the best way to do that is. I wrote a script, which would do it in
>> theory, but I haven't tested because I only have one system and if
>> it breaks it the only way back would be to reinstall.
>>
>> The script is attached.
>>
>>
>> Thoughts on any of this?
>
>
> This was invented in Solaris and copied by RHEL. The upgrade
> path for the /usr merge on those systems is a complete
> reinstall. Upgrading from RHEL6 to RHEL7 this Solaris 10 to
> Solaris 11 is not supported. The reason being that there are
> ways of configuring the system boot process with the original
> layout that break if you try using scripts to migrate to the new
> one. A USE flag for the /usr merge that is off by default would
> allow us to have both worlds without putting any systems at
> risk.

that's what i'm actually more worried about: the fact they failed to have a 
proper upgrade path doesnt mean it is impossible, just that it is not easy.

only being able to propose usr-merge for new installs makes it useless for 
gentoo imho: i, for once, use only 1 gentoo install for the lifetime of my 
/ disk...


note that being able to properly migrate is a *requirement* for having it 
as a useflag

> If others are not willing to be advocates for those users that
> would only make themselves known after an a fundamental change
> has been made and people are determined to go ahead with this, I
> suggest having and testing a plan for backing out the change
> should the backlash from users after systems break be more than
> people can stomach. This is not the sort of change we should
> make without an "exit strategy".


ironing out that kind of strategy is the point of this thread :)

Alexis.