I know in /etc/yum.conf there is a throttle command.
is there a like feature in /etc/sysconfig/uln-yum-mirror?
Just set the throttle parameter in yum.conf: uln-yum-mirror is just a bash script that calls reposync which uses yum to download and it will use the configuration in /etc/yum.conf.
did you have to restart something for the changes to take effect?
It won't have any effect if there is a uln-yum-mirror run in progress (or at least, for the duration of any running reposync). I tested it by editing /etc/yum.conf and then running reposync manually, which is the same as what the uln-yum-mirror script does. It definitely worked fine for me.
# This is the default, if you make this bigger yum won't see if the metadata
# is newer on the remote and so you'll "gain" the bandwidth of not having to
# download the new metadata and "pay" for it by yum not having correct
# It is esp. important, to have correct metadata, for distributions like
# Fedora which don't keep old packages around. If you don't like this checking
# interupting your command line usage, it's much better to have something
# manually check the metadata once an hour (yum-updatesd will do this).
# PUT YOUR REPOS HERE OR IN separate files named file.repo
# in /etc/yum.repos.d
I don't use the bandwidth/throttle combo, just throttle, so I added "throttle=1M" into mine (and I also tested 2M, 10M and 20M). Considering I was testing on a machine that was local to the yum server it was using, it was pretty obvious to see reposync honour that setting. In your case, I'd try "throttle=125k" which is 25% of 500k anyway.
I've found the answer. Because ULN uses the same code as the upstream RHN code, you need to specify a throttle value for each channel you're mirroring from ULN. This means that you need to edit /etc/yum/pluginconf.d/rhnplugin.conf and add a stanza for each repo and adding a throttle setting for each one. If you followed the uln-yum-mirror setup instructions, you probably have a stanza for each channel already to disable it, so you can just add the throttle value to each stanza.
See https://access.redhat.com/site/discussions/671423 for a discussion of the same issue on the upstream distro.