[CentOS-devel] CentOS Upgrade Tool

On Wed, Jan 6, 2016 at 7:24 AM, Bruno Martins <bruno.martins at rumos.pt> wrote:
> I've used the tool with '--force' parameter and it upgraded just fine. Now I'm having some side effects like:
> "grep: error while loading shared libraries: libpcre.so.0: cannot open shared object file: No such file or directory"

I had a similar issue with grep when I upgraded my CentOS 6 home
server to CentOS 7 last week. As explained elsewhere, the issue is
that not all .el6 packages get upgraded.

To fix it, after I did the OS upgrade to CentOS 7:

- Generate a list of all packages with "rpm -qa",
- Note each of the ".el6" ones,
- Download the ".el7" equivalents from a CentOS mirror by hand,
- Install the .el7 versions with "rpm --force" (so RPM thinks you have
both versions installed)
- Use yum to remove the ".el6" versions.

There are some packages like python-argparse that don't have a direct
equivalent in CentOS 7 (the argparse library is provided by the core
python-2.7 package), so those are simply safe to remove outright. You
might find that there's other crufty el6 packages left behind on your
server that you don't need.

I host my OS (/boot and /) on software RAID1 (with mdadm), and for a
while, the first el7 kernel I installed didn't add both drives to the
array devices during boots, which made me wonder if the drives were
dying. But it just turned out to be a software issue (maybe something
in the very first initrd generation went awry?), because after I ran
"yum update" to get the latest el7 kernel, it worked fine.

Once you finish the OS upgrade, if you see problems during operation,
start with checking "rpm -qa" for "el6" and then working through the
individual packages one-by-one. (you'll probably want to start with
fixing "grep", since it's tedious to work without it :)

- Ken