Hi Takashi ichihara!

 On 2017.10.03 at 11:28:46 +0900, Takashi ichihara wrote next:

> We have several SL7.3 nodes installed with yum-conf-sl7x.
> Today I noticed that some of them cannot be updated
> from SL7.3 to SL7.4 by the foll wing simple steps.
> 
> # yum clean all
> # yum yum install.
> 
> With several trials, I noticed that following procedure
> works fine to update from SL7.3 to SL7.4.
> 
> # yum remove yum-conf-sl7x
> # yum install yum-conf-sl7x
> # yum clean all
> # yum update

Systems that couldn't be upgrade were probably release-locked to 7.3.
You can check it by doing
$ cat /etc/yum/vars/slreleasever
7.3

If it says 7.3 there - it's release-locked. Just do
# echo 7.4 > /etc/yum/vars/slreleasever

and next "yum update" will update the version (and will be locked to it). Or you can do
# echo 7x > /etc/yum/vars/slreleasever

and you will have unlocked version that will get all next releases
automatically as well. Which is what reinstalling yum-conf-sl7x actually
does, because it ships with "7x" in that "/etc/yum/vars/slreleasever".

But yum-conf-sl7x package is designed such way so it won't release lock
on systems where it was activated. In other words, if "7.3" was manually
written to that file before, update of that package won't put "7x"
there. But removing and installing package anew effectively defeats that
logic.

Release lock is designed so that some random systems won't upgrade
overnight without your actions. However, given that most serious updates from 7.4
like glibc or kernel arrive as security updates for 7.3 in a big pack
anyway, I can't say that it's terribly useful.

-- 

Vladimir