From 741ad15f3b83e18b4009c42a287151e14f60fed1 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Sat, 7 Jul 2018 08:10:47 +0900
Subject: [PATCH] Add note in pg_rewind documentation about read-only files
When performing pg_rewind, the presence of a read-only file which is not
accessible for writes will cause a failure while processing. This can
cause the control file of the target data folder to be truncated,
causing it to not be reusable with a successive run.
Also, when pg_rewind fails mid-flight, there is likely no way to be able
to recover the target data folder anyway, in which case a new base
backup is the best option. A note is added in the documentation as
well about.
Reported-by: Christian H.
Author: Michael Paquier
Reviewed-by: Andrew Dunstan
Discussion: https://postgr.es/m/20180104200633.17004.16377%40wrigleys.postgresql.org
---
doc/src/sgml/ref/pg_rewind.sgml | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/doc/src/sgml/ref/pg_rewind.sgml b/doc/src/sgml/ref/pg_rewind.sgml
index 42ebfbfdef8..32e6d0445f6 100644
--- a/doc/src/sgml/ref/pg_rewind.sgml
+++ b/doc/src/sgml/ref/pg_rewind.sgml
@@ -95,6 +95,26 @@ PostgreSQL documentation
are currently on by default. <xref linkend="guc-full-page-writes">
must also be set to <literal>on</>, but is enabled by default.
</para>
+
+ <warning>
+ <para>
+ If <application>pg_rewind</application> fails while processing, then
+ the data folder of the target is likely not in a state that can be
+ recovered. In such a case, taking a new fresh backup is recommended.
+ </para>
+
+ <para>
+ <application>pg_rewind</application> will fail immediately if it finds
+ files it cannot write directly to. This can happen for example when
+ the source and the target server use the same file mapping for read-only
+ SSL keys and certificates. If such files are present on the target server
+ it is recommended to remove them before running
+ <application>pg_rewind</application>. After doing the rewind, some of
+ those files may have been copied from the source, in which case it may
+ be necessary to remove the data copied and restore back the set of links
+ used before the rewind.
+ </para>
+ </warning>
</refsect1>
<refsect1>
--
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