error when upgrading 9.4 to 9.5 manually

My box upgraded postgresql from 9.4.8 to 9.5.3 when doing a full
version upgrade (Fedora 23 --> 24).

I have now :

/db/pgsal/data ----> initialized with 9.5, with postgresql.conf and
pg_hab.conf from 9.4
/db/pgsql/data.old ----> the old one from 9.4

/usr/lib64/pgsql/postgresql-9.4/bin which comes from
postgresql-upgrade Fedora package.
$ ls /usr/lib64/pgsql/postgresql-9.4/bin
drwxr-xr-x 1 root root 22 Jul 7 09:21 ../
-rwxr-xr-x 1 root root 28K May 12 15:34 pg_controldata*
-rwxr-xr-x 1 root root 41K May 12 15:34 pg_ctl*
-rwxr-xr-x 1 root root 29K May 12 15:34 pg_isready*
-rwxr-xr-x 1 root root 45K May 12 15:34 pg_receivexlog*
-rwxr-xr-x 1 root root 49K May 12 15:34 pg_recvlogical*
-rwxr-xr-x 1 root root 36K May 12 15:34 pg_resetxlog*
-rwxr-xr-x 1 root root 5.8M May 12 15:34 postgres*
lrwxrwxrwx 1 root root 8 May 12 15:33 postmaster -> postgres*

Now I think I shall run this command with postgres off
:

$ pg_upgrade -b /usr/lib64/pgsql/postgresql-9.4/bin -B /usr/bin -d
/db/pgsql/data.old -D /db/pgsql/data
But it reurns this error:

connection to database failed: could not connect to server: No such
file or directory
Is the server running locally and accepting
connections on Unix domain socket "/db/pgsql/.s.PGSQL.50432"?

could not connect to old postmaster started with the command:
"/usr/lib64/pgsql/postgresql-9.4/bin/pg_ctl" -w -l
"pg_upgrade_server.log" -D "/db/pgsql/data.old" -o "-p 50432 -b -c
listen_addresses='' -c unix_socket_permissions=0700 -c
unix_socket_directories='/db/pgsql'" start
--------------------------------------

Posgresql is started with systemd service file and its socket is in
/run/postgresql

How can I start postgres with socket location in /db/pgsql ? There is
no option in pg_ctl to indicate socket directory.?

Thank you for help

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