Create multiple Postgres instances on same machine - postgresql

Question

To test streaming replication, I would like to create a second Postgres instance on the same machine. The idea is that if it can be done on the test server, then it should be trivial to set it up on the two production servers.
The instances should use different configuration files and different data directories. I tried following the instructions here http://ubuntuforums.org/showthread.php?t=1431697 but I haven't figured out how to get Postgres to use a different configuration file. If I copy the init script, the scripts are just aliases to the same Postgres instance.
I'm using Postgres 9.3 and the Postgres help pages say to specify the configuration file on the postgres command line. I'm not really sure what this means. Am I supposed to install some client for this to work? Thanks.

Answer 1

I assume you can work your way out on using postgresql utilities.
Create the clusters
$ initdb -D /path/to/datadb1
$ initdb -D /path/to/datadb2
Run the instances
$ pg_ctl -D /path/to/datadb1 -o "-p 5433" -l /path/to/logdb1 start
$ pg_ctl -D /path/to/datadb2 -o "-p 5434" -l /path/to/logdb2 start
Test streaming
Now you have two instances running on ports 5433 and 5434. Configuration files for them are in data dirs specified by initdb. Tweak them for streaming replication.
Your default installation remains untouched in port 5432.

Answer 2

On Debian based distros you could use pg_createcluster instead of initdb:
$ pg_createcluster -u [user] -g [group] -d /path/to/data -l /path/to/log -p 5433
Also pg_ctlcluster is an alternative to pg_ctl.

Answer 3

Steps to create New Server Instance on PostgreSQL 9.5
On command prompt run:
initdb -D Instance_Directory_path -U username -W
(prompts for password)
Once the new Instance Directory is created. Run command prompt as Administrator
pg_ctl register -N service_name -D Instance_Directory_path -o "-p port_no"
After the service is registered, start server
pg_ctl start -D Instance_Directory_path -o "-p port_no"

Answer 4

To complete other answers, on CentOS 6 AND 7.
After running something like
$ initdb -D /path/to/newdb
You'll have to change at least port configuration option and, probably, listen_addresses in config file postgresql.conf.
Instead of starting inmediatly this new instance, which has been explained in previous answers, maybe you want new instance to run automatically on system start (in case of shutdown, e.g.). To do this, as CentOS doesn't have pg_ctl register option (only for Windows) you'll have to create a new service file and register it in order systemctl or service can start it up automatically.
Centos 6
Follow next commands to get service's init file:
[root#machine ~]# service postgresql-9.6 edit
Usage: /etc/init.d/postgresql-9.6 {start|stop|status|restart|upgrade|condrestart|try-restart|reload|force-reload|initdb|promote}
[root#machine ~]# cd /etc/init.d # Now we know where service file is
[root#machine init.d]# cp -p postgresql-9.6 postgresql-9.6_5433
[root#machine init.d]# vi postgresql-9.6_5433
Now you can change PGDATA directory with the one where new instance resides. If you're using Postgresql version previous to 9.4 (which you shouldn't by the time of this answer) you'll have to change PGPORT too with the value where new instance is listening to.
The name of the new service is up to you. I usually take original service name and add port number at the end.
Now you only have to register new service:
[root#machine init.d]# chkconfig postgresql-9.6_5433 on # service registered!
[root#machine init.d]# service postgresql-9.6_5433 start
Iniciando servicios postgresql-9.6_5433: [ OK ]
[root#machine init.d]# service postgresql-9.6_5433 status
Se está ejecutando postgresql-9.6_5433 (pid 120993)...
Centos 7
In CentOS 7 instead of service to control services running on the machine you have systemctl and commands and paths change a bit. But the process is the same: create new service file, edit with the new location/port, register and start:
[root#localhost ~]# locate postgresql.service
/etc/systemd/system/multi-user.target.wants/postgresql.service
/usr/lib/systemd/system/postgresql.service
[root#localhost ~]# cd /usr/lib/systemd/system
[root#localhost ~]# cp -p postgresql.service postgresql_5433.service
[root#localhost ~]# vi postgresql_5433.service
# Change PGDATA and maybe PGPORT if PG version <9.4
[root#localhost ~]# systemctl enable postgresql_5433.service
[root#localhost ~]# systemctl start postgresql_5433.service
[root#localhost ~]# systemctl list-unit-files | grep postgres
postgresql.service enabled
postgresql_5433.service enabled