Partitioning an existing table - pg10.6

Hello, I am using postgres 10.6 and have a huge table with ~30m recs which
needs to be partitioned. Whats the best strategy for it with minimal
downtime?

1. Rename existing table and create new partitioned tables with orig name
and keep inserting data from the old renamed to new table. This will incur
downtime for the apps.
2. Create partitioned table with new name and move the data from current
table (move oldest to newest) and when moving current month paritition
shutdown down the app and move the last set of data. This will not incur
downtime but if any data is changed which was already copied over then it
might be lost.

Any other approaches/alternatives?

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Regards,
Ayub