Command to validate a postgresql configuration file?

Question

I am generating postgresql configuration files via ansible, and putting them in /etc/postgresql/XX/main/conf.d/whatever.conf. I accidentally made a syntax error and broke my postgresql, requiring manual fixing.

Is there any postgresql command to validate that a file is a valid postgresql.conf file?

sudoers files can be validates with /usr/sbin/visudo -cf path/to/file. Is there anything for postgresql?

I'm currently running Ubuntu 18.04 & 20.04, with PostgreSQL 10, 12 etc (yes several different versions).

Answer 1

Yes.

At least as of version 10 there is a mechanism to check the config file from within postgres.

This is the result of adding a fubar to my config file, didn't reload it.

postgres=# select sourcefile, name, sourceline, error from 
 pg_file_settings where error is not null;
 sourcefile | name | sourceline | error
-----------------------------------------+------+------------+--------------
 /etc/postgresql/12/main/postgresql.conf | | 33 | syntax error
(1 row)

Docs will be: https://www.postgresql.org/docs/10/view-pg-file-settings.html, also, you might be interested in https://www.postgresql.org/docs/10/view-pg-hba-file-rules.html

• Stanislav Bashkyrtsev: But you have to start PG for this..
• Laurenz Albe: Oh, great, I have learned something new!
• jjanes: @StanislavBashkyrtsev If it is not running, then start it. If it starts, the file is valid. I think the problem he wants to solve is not shutting down the running server until he knows it will be able to start again. If it is already down, that isn't much of an issue.
• reducing activity: In my case it is not running and I am trying to discover why.
• Eugen Konkov: Could it be possible to check why the settings was not applied? /dbdata/postgres/postgresql.conf | 820 | 20 | archive_mode | off | f | setting could not be applied

Answer 2

The only program that I know is postgres, the database server.

I have two approaches to deal with that problem:

• After you edit postgresql.conf and reload, examine the PostgreSQL log file. If there was a problem, you will see that in the log, an the server will keep running with the previous configuration (no outage). Fix the file and try again until it the reload is successful.

• Use ALTER SYSTEM rather than postgresql.conf to change configuration parameters. That works just as well, and ALTER SYSTEM will catch most of the possible syntax errors. Of course, you should still look at the PostgreSQL log after reloading.

As an alternative to checking the log file, you may use the pg_file_settings view as described in the other answer.

• reducing activity: "examine the PostgreSQL log file" - the irony is that I was trying to enable logging and instead pgsql is not starting at all.
• Laurenz Albe: Yes, but it is producing errors that explain why it refuses to start.
• reducing activity: Maybe, but I have no idea where it logs this problems.

Answer 3

With the command postgres (see man postgres for details) you can query a config parameter and if something in one of the config files is invalid, it shows an error.

Example Postgresql version 12 on Debian as user postgres:

$ /usr/lib/postgresql/12/bin/postgres --config-file=/etc/postgresql/12/main/postgresql.conf -C data_directory
/var/lib/postgresql/13/main
$ echo $?
0

now with an error in the config:

$ /usr/lib/postgresql/12/bin/postgres --config-file=/etc/postgresql/12/main/postgresql.conf -C data_directory
2023年03月31日 11:15:22.550 [5041] LOG: unrecognized configuration parameter "unknown" in file "/etc/postgresql/12/main/conf.d/example_error.conf" line 2
2023年03月31日 11:15:22.550 [5041] FATAL: configuration file "/etc/postgresql/12/main/conf.d/example_error.conf" contains errors
$ echo $?
1

• Larsen: Best way if you want to automate things.