Re: Documentation for initdb option --waldir

On Sat, Mar 29, 2025 at 10:58 AM David G. Johnston
<david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
> On Saturday, March 29, 2025, Robert Treat <rob(at)xzilla(dot)net> wrote:
>>
>> On Thu, Mar 27, 2025 at 5:57 PM David G. Johnston
>> <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>> > On Thu, Mar 27, 2025 at 2:28 PM Robert Treat <rob(at)xzilla(dot)net> wrote:
>> >> On Thu, Mar 27, 2025 at 12:06 PM David G. Johnston
>> >> <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>> >> > I expanded upon the material regarding using different file systems and disks.
>> >> >
>> >> > I would like to add a similar "why" to the mount point recommendation but don't know what that would be. Suggestions welcomed.
>> >> >
>> >>
>> >
>> > If I mount the filesystem on disk2 to: /mnt/disk2
>> > Why do I need to create "/mnt/disk2/wal_files/" and point there instead of: "/mnt/disk2/"?
>> >
>>
>> eventually came across this from
>> https://www.postgresql.org/docs/devel/creating-cluster.html#CREATING-CLUSTER-MOUNT-POINTS
>>
>> "Best practice is to create a directory within the mount-point
>> directory that is owned by the PostgreSQL user, and then create the
>> data directory within that. This avoids permissions problems,..."
>>
>> Which I do remember having tried to do it directly and the OS
>> complaining that my mount point wasn't owned by root and/or Postgres
>> complaining that the xlog dir wasn't owned by Postgres, so I think
>> this advice probably still holds.
>>
>
> Thank you, I can definitely work that in and it makes sense.
>
> On the topic of verbosity, I found the wording for —pgdata in pg_basebackup to support the more complete description.
>
> https://www.postgresql.org/docs/current/app-pgbasebackup.html
>
> I believe that at least documenting external side-effects should be required. I’m less convinced that pre-conditions that will be checked by the application need to be listed. But for now I’m going to copy pg_basebackup as my example and at some point might get to doing a survey and proposing a new standard wording for —waldir and —pgdata descriptions regarding creation.
>
> The comment regarding absolute paths will remain unwritten.
>

Works for me.

Robert Treat
https://xzilla.net