Re: Switching from 9.1 to 9.5 on Ubuntu 16.04

Mike,

>>2) If yes then stop 9.1 server and make sure only postgres 9.5 is in
active state(you can do this as "su postgres" user)

>Not sure what you mean? Not sure how to stop one server without stopping
another. Typically I use sudo service postgres stop/start/restart and that
seems to work on all together.

See, in /etc/init.d/ folder postgres is created as service so action on that
service will be equivalently effected for all the postgres instances on this
server. For example you do have postgres 9.1,9.3,9.5 on the same ubuntu
server and if you issue:
service postgresql start/stop/restart
it will actually affect all the 3 instances. So you need to be specific and
issue command(as previously said) like :
/usr/lib/postgresql/9.5/bin/pg_ctl -D "/var/lib/postgresql/9.5/main" start
/usr/lib/postgresql/9.5/bin/pg_ctl -D "/var/lib/postgresql/9.5/main" stop
etc...

Note: for issuing above commands you should be postgres user(from OS level
and DB level)

>>>createdb --port=5432 --host=pq4 --template=template0 --encoding=UTF8
--lc-collate=C --lc-ctype=C --username=miked --owner=miked train

>>3) Ensure the active listening postgres ports on the server by:
>> netstat -alp | grep "5432"
>>

>mike(at)pq4:~$ netstat -alp | grep "543"
>(Not all processes could be identified, non-owned process info
> will not be shown, you would have to be root to see it all.)
>tcp 0 0 localhost:5431 *:* LISTEN
-
>tcp 0 0 pq4:5431 *:*
LISTEN -
>tcp 0 0 localhost:5433 *:* LISTEN
-
>unix 2 [ ACC ] STREAM LISTENING 31377 -
/var/run/postgresql/.s.PGSQL.5432
>unix 2 [ ACC ] STREAM LISTENING 31378 -
/var/run/postgresql/.s.PGSQL.5433
>unix 2 [ ACC ] STREAM LISTENING 31438 -
/var/run/postgresql/.s.PGSQL.5431
>mike(at)pq4:~$

From the above output you are trying to create a database on database port
5432 which is not active. Postgres is unable to understand how to create a
database on a closed port(which is not going to work for sure). Ensure
yourself that the port on which you are creating database is in open state
and accepting client requests.

>>4) Later as same "su postgres user"
>>
>mike(at)pq4:~$ su postgres
>Password:
>su: Authentication failure
>mike(at)pq4:~$ su postgres user
>Password:
>su: Authentication failure
>mike(at)pq4:~$ sudo -u postgres psql
>could not change directory to "/home/mike": Permission denied
>psql (9.5.14)
>Type "help" for help.
>
>postgres=# \password postgres
>Enter new password:
>Enter it again:
>postgres=# \q
>mike(at)pq4:~$ su postgres
>Password:
>su: Authentication failure
>mike(at)pq4:~$
>
>As you can see I don't know how to change the postgres user password. Did
it a few times just to be sure.

Firstly, do you have root access for that server?

If yes, you can issue sudo bash as the user(you will login to the server)
and then you can change the password for the OS level postgres user like
below:

[root(at)pg4]# passwd postgres
Changing password for user postgres.
New password:
Confirm New password:

then password will be changed for that user and can try logging in as :
[root(at)pg4]# su postgres
[postgres(at)pg4]#

Now issue the above said commands

/usr/lib/postgresql/9.5/bin/pg_ctl -D "/var/lib/postgresql/9.5/main" start
/usr/lib/postgresql/9.5/bin/pg_ctl -D "/var/lib/postgresql/9.5/main" stop
etc..

Which will work for sure...

>What I would like to do is uninstall 9.1 and 9.3. How would I do that?
issue the below command:
*dpkg -l | grep postgresql *

Consider removing the postgres versions you like to remove!! Anyways this is
not a proper fix for your prob.

Jus ensure the port is listening on your server to execute your createdb
command. Acknowledge for further queries if any.

Regards,
Pavan,
9841380956

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