Re: pg_basebackup ignores the existing data directory permissions

On Fri, Feb 15, 2019 at 10:15 AM Michael Paquier <michael@paquier.xyz> wrote:

On Thu, Feb 14, 2019 at 11:21:19PM +1100, Haribabu Kommi wrote:
> On Thu, Feb 14, 2019 at 8:57 PM Magnus Hagander <magnus@hagander.net> wrote:
>> I think it could be argued that neither initdb *or* pg_basebackup should
>> change the permissions on an existing directory, because the admin may have
>> done that intentionally. But when they do create the directory, they should
>> follow the same patterns.
>
> Hmm, even if the administrator set some specific permissions to the data
> directory, PostgreSQL server doesn't allow server to start if the
> permissions are not (0700) for versions less than 11 and (0700 or
> 0750) for version 11 or later.

Yes, particularly with pg_basebackup -R this adds an extra step in the
user flow.

> To let the user to use the PostgreSQL server, user must change the
> permissions of the data directory. So, I don't see a problem in
> changing the permissions by these tools.

I certainly agree with the point of Magnus that both tools should
behave consistently, and I cannot actually imagine why it would be
useful for an admin to keep a more permissive data folder while all
the contents already have umasks set at the same level as the primary
(or what initdb has been told to use), but perhaps I lack imagination.
If we doubt about potential user impact, the usual, best, answer is to
let back-branches behave the way they do now, and only do something on
HEAD.

I also agree that both inidb and pg_basebackup should behave same.

Our main concern is that standby data directory that doesn't follow

the primary data directory permissions can lead failures when the standby

gets promoted.