Does postgres single-user mode use postgresql.conf settings?

Question

Does running postgres in single-user mode (--single argument) cause postgres to start and use the settings present in the postgresql.conf file in the data directory defined by the -D option?

I am doing some maintenance with postgres in single user mode. I want to ensure that while running in single user mode that it has the correct resource allocation available. I have already set these resources in postgresql.conf and the work as expected when running in normal (not single-user) mode. Is the same config file used when running in single-user mode as long as its present in the defined data directory?

My specific goal is to run a VACUUM FREEZE on a 1.6TB table to cope with a multixact wraparound issue. My postgresql.conf is loaded up with higher than normal (for us) maintenance_work_mem settings. If these settings are not read when running in single-user mode I need to know so I can apply them manually using the -c flag I think. I am specifically seeking an answer as to if the config is loaded, Q&A about my FREEZE or specific tuning should happen elsewhere.

I think I could verify this with pg_settings however I am now 3 hours in to a long running maintenance operation. I would prefer not to stop and restart that maintenance if another user or a manpage will confirm that my postgresql.conf settings are applied.

I am running PG 9.4.5

Answer 1

Yes, postgresql.conf and postgresql.auto.conf will be read and used in single-user mode as usual.

Parameters you specify with -c options will override the settings from the configuration files.

You are doing the right thing.