[scl.org] 2 questions on software collections

Langdon White langdon at redhat.com
Wed Jan 6 14:00:55 UTC 2016

On 01/06/2016 08:27 AM, Honza Horak wrote:
> On 01/05/2016 05:22 PM, Langdon White wrote:
>> On 01/05/2016 11:00 AM, Jim Perrin wrote:
>>> On 01/04/2016 02:22 PM, Langdon White wrote:
>>>>> 2nd: how do I switch permanently to the version of the sotfware
>>>>> collection for a user? If I run
>>>>> $ scl enable rh-perl520 bash
>>>>> after logging off and on I get back to system perl version. Adding
>>>>> that line to ~/.bash_profile seems to do the trick. Is this the
>>>>> correct way to do it?
>>>> I wrote a quick blog post about this some time back. I think this is
>>>> still something we would like to see a better solution(s) for.
>>>> http://developerblog.redhat.com/2014/03/19/permanently-enable-a-software-collection/ 
>>> It would be interesting to see if it's possible to easily expand the
>>> scope of the alternatives framework to include scls. This way admins
>>> could take what they already use for java and use it to manage scl
>>> version choices as well.
>> Yeah.. I have thought about that a bunch too.. but haven't had a chance
>> to look at it...
>> I know some people have had success with mucking about using environment
>> modules (IIRC the name), ncoghlan comes to mind....
> Environment modules is the implementation behind the newer scl-utils 
> 2.0 (available just in Fedora, not RHEL yet). With that, something 
> like this should be possible to do:
>    module initadd <sclname>
> The `alternatives` is not something I'd recommend, because that is 
> based on creating system-wide symlinks. So, e.g. creating 
> /usr/bin/python that would be actually python SCL binary (or wrapper) 
> is not a good thing to do. That is not how SCLs were designed to be 
> used. SCLs were designed to be used only when someone asks for 
> `python`, but /usr/bin/python should always point to system python.

Yeah, I think we tend to hyper-focus on the python use case, if we were 
talking ruby or apache it might be better. So, while it may never work 
for some scls (and I definitely know it is how it wasn't intended to be 
used) it might be worthwhile to investigate if it works. Even though it 
kinda flies in the face of "running two versions at the same time."


> Honza
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