Help: Installing 9.6 breaks local connections to 9.2 on Centos 6.9

Hi. On a Centos 6.9 server (in the cloud with Rackspace), I'm wanting to
install PGDG 9.6 alongside the already-running 9.2. After installing the
9.6 packages (and even before doing an initdb), I am no
longer able to make a local connection to the 9.2 server. Instead I get
the message:

psql: could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

That socket file does not exist on the server. (And in fact, the
/var/run/postgresql directory didn't exist before installing 9.6). When I
configure 9.6 to use port 5433 and run it, it does create that socket for
5433. I tried creating such a socket manually for 5432, but that didn't
seem to change anything.

Any help in getting this working and/or pointing out what I'm missing would
be great. I'm also confused conceptually about what is happening here.
What is it that the installation (but not execution) of 9.6 does that's
blocking the local 9.2 access? I'm guessing it's gotta be something in the
RPM install scripts.

Thanks!

Ken

bash-4.1$ whoami
postgres
bash-4.1$ psql -p 5432
psql: could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
bash-4.1$ psql -p 5432 -h localhost
Password:
bash-4.1$ psql -p 5433
psql (9.6.3)
Type "help" for help.

postgres=# \q
bash-4.1$ /usr/pgsql-9.2/bin/psql -p 5432
psql: could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
bash-4.1$ /usr/pgsql-9.6/bin/psql -p 5432
psql: could not connect to server: Connection refused
Is the server running locally and accepting
connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

[root(at)centos-new postgresql]# cat /etc/issue
CentOS release 6.9 (Final)
Kernel \r on an \m

[root(at)centos-new postgresql]# yum list installed "postgresql*"
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: centos.mirror.lstn.net
* extras: centos.mirror.lstn.net
* updates: centos.mirror.lstn.net
Installed Packages
postgresql92.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-contrib.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-devel.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-docs.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-libs.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-plpython.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-pltcl.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql92-server.x86_64 9.2.21-1PGDG.rhel6
@pgdg92
postgresql96.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
postgresql96-contrib.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
postgresql96-devel.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
postgresql96-docs.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
postgresql96-libs.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
postgresql96-pltcl.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
postgresql96-server.x86_64 9.6.3-1PGDG.rhel6
@pgdg96
[root(at)centos-new postgresql]#

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