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Re: Trouble setting up replication

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> On Sep 5, 2015, at 4:29 PM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote:
> 
> On 09/05/2015 11:00 AM, Chuck Martin wrote:
>> Thanks for responding Adrian.
>> 
>> After writing this, I noticed that the list is configure to reply to sender. I hope this is not inappropriate. Please tell me if I should re-send changing the address to the list.
> 
> The best way to do it is to use Reply All. This sends to both the list and the user. Ensures the user gets the email even if the list is running slow. While we are list etiquette, the custom on the list is to not top post.

I’ll follow these customs in the future. 

>> [snip] Other then init scripts you should not be doing anything with Postgres as root.

That is the cause of many of the problems I’ve experienced, and I’ll avoid that now.

> [snip]
>> WARNING:  could not read symbolic link "pg_tblspc/pg_hba.conf": Invalid argument
> 
> pg_tblspc contain symlinks to tablespaces. pg_hba.conf is a configuration file, it should not be there. Looks like pg_basebackup ignored it, but it would worth checking out what else is in pg_tblspc in the database cluster you are backing up from.

Thanks. I’ll research this.

>> [snip]
>> Could I have run pg_basebackup on the replicant/slave over ssh? I thought I could, and when I tried, the results suggest it is possible, but my configuration of one or the other server was incorrect. Can you see what I had wrong from this:
>> 
>> pg_basebackup -h [main_server_url] -D /var/lib/pgsql/9.3/backups/rep -P -v -X s
>> pg_basebackup: could not connect to server: FATAL:  no pg_hba.conf entry for replication connection from host “[my replicant server’s outside IP]", user "root", SSL on
>> FATAL:  no pg_hba.conf entry for replication connection from host "[my replicant server’s outside IP]", user "root", SSL off
>> 
>> I had added to my pg_hba.conf
>> 
>> host    replication     rep     64.207.10.121/32   cert
> 
> From the above the only user that can use replication connecting from 64.207.10.121/32 is rep. You did not specify a -U in your connection above and ran the command as root so pg_basebackup used that as the user, which is the default behavior:
> 
> http://www.postgresql.org/docs/9.4/interactive/libpq-connect.html#LIBPQ-PARAMKEYWORDS
> "
> user
> 
>    PostgreSQL user name to connect as. Defaults to be the same as the operating system name of the user running the application.
> "
> 
> There is no pg_hba entry for database replication and user root so the connection was rejected. To repeat, get out of the habit of running Postgres commands as root, it is not necessary. What matters is the Postgres user you are connecting as. When using replication, which is what pg_basebackup is doing, you need to connect as a user with sufficient privileges:
> 
> http://www.postgresql.org/docs/9.4/interactive/app-pgbasebackup.html
> 
> ".. The connection must be made with a superuser or a user having REPLICATION permissions (see Section 20.2), and pg_hba.conf must explicitly permit the replication connection. .."
> 
> Whatever user you choose to do this with then needs to authorized in pg_hba.conf.

This is very helpful. I understood that pb_basebackup was for creating a backup for replication purposes, but did not understand that PG needs the same permissions for it as for the replication itself. I ran it as user “postgres” and not as “rep”. I think I understand my error, but will study the links you included to make sure. 

Thanks for your help, Adrian. I think I’ll get this working now. 

Chuck



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