Ekaterina Amez <ekaterina(dot)amez(at)zunibal(dot)com> writes:
> I'm installing postgres 9.6 in a CentOS 7 computer that already has
> postgres v9.2 installed (version that comes with CentOS installer) and
> I've seen the message of this mail's subject.
> ...
> failed to link /usr/bin/psql -> /etc/alternatives/pgsql-psql: /usr/bin/psql exists and it is not a symlink
> ...
I believe the issue here is that you've got Red Hat's postgresql packages
installed, and they're not set up to participate in alternatives
switching. I'd suggest removing those packages --- having them installed
alongside PGDG postgres packages is going to lead to nothing but grief.
regards, tom lane