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

1 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.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.