document how to add gems to OnDemand

[johrstrom]

From OnDemand: OSC/ondemand#3452

Let's say a user/center wants to add a gem to be used in a partial/widget/whatever, we don't currently have a good understanding of how to do this and we definitely don't have the documentation for the same.

This ticket is to do both - find the real solution that'll work on Debian and RHEL systems and then also document it here.

[treydock]

The solution should be the same for RHEL and Debian as we removed a dependency on SCL in RHEL.

source /opt/ood/ondemand/enable

gem install <thing>

[epruesse]

I currently have this to add argon2 to the dashboard gems (argon2 is required to make the auth cookie for vs-code/code-server):

ONDEMAND_GEMS=argon2
dnf -y install gcc
scl enable ondemand -- gem install $ONDEMAND_GEMS 
cd /var/www/ood/apps/sys/dashboard/ 
scl enable ondemand -- bundle add $ONDEMAND_GEMS 

(Disclaimer: I don't really know what I'm doing, I just found something that worked ;-) )

[treydock]

I think for adding gems to dashboard, we need to provide a better mechanism to do that as the gems for a given app are supposed to be somewhat immutable and part of the RPM. The SCL environment however was always intended to be something sites could modify.

What version are you doing the scl enable ondemand with? We run 4.0.x and no longer depend on scl so my guess is you're on 3.1 or older.