Installation placed on read only partition

Hi!
I would like to install postgresql on a Linux system where as much as
possible of the OS- and program specific directories will be turned read
only after installation.
My intent is to place all files that needs to be writable on a second,
read/write partition.

My question is:
Is there some files and/or directories in the postgresql installation that
has to remain writable after installation?
Of course, the directory pointed out by initdb -D will be in the read/write
partition, and the same goes for the file pointed out by the -l flag for
pg_ctl.

Thanks in advance!

Best regards,
Fredrik Israelsson

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