On Mon, Jun 29, 2015 at 4:55 AM, Heikki Linnakangas wrote: > After thinking about this some more, I think it'd be acceptable if we just > fail, if there are any non-writeable files in the data directory. The > typical scenario is that postgresql.conf, or an SSL cert file, is a symlink > to outside the data directory. It seems reasonable to require that the DBA > just removes the symlink before running pg_rewind, and restores it > afterwards if appropriate. In many cases, you would *not* want to overwrite > your config files, SSL cert files, etc., so the DBA will need to script > backing up and restoring those anyway.
Outnumbered I surrender. We are on the way of a doc patch then as pg_rewind already fails in this scenario when trying to open the target. What about the attached? > (It's a fair question whether pg_rewind should be copying those files in the > first place. I've opted for "yes", so that it's easy to explain the > behaviour of pg_rewind: the end result is the same as if you took a new base > backup from the source server. Whatever files you want to backup up before > you re-initialize from a base backup, you should also backup with > pg_rewind.) We could then ignore all the symlinks in PGDATA except the ones that are related to tablespaces, that's where the use of missing_ok for pg_tablespace_location makes sense. pg_readlink would be useful for pg_xlog in any case either way. > But we'll still need to handle the pg_xlog symlink case somehow. Perhaps it > would be enough to special-case pg_xlog for now. Well, sure, pg_rewind does not copy the soft links either way. Now it would be nice to have an option to be able to recreate the soft link of at least pg_xlog even if it can be scripted as well after a run. Regards, -- Michael
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml index 32dc83f..92325f3 100644 --- a/doc/src/sgml/ref/pg_rewind.sgml +++ b/doc/src/sgml/ref/pg_rewind.sgml @@ -234,4 +234,15 @@ PostgreSQL documentation </refsect2> </refsect1> + <refsect1> + <title>Notes</title> + + <para> + Read-only files cannot be included in the data directory of target + instance before starting <application>pg_rewind</>. For example, soft + links to read-only files should be temporarily removed from the data + directory and added back after the process. + </para> + </refsect1> + </refentry>
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