bitbake: bitbake-user-manual/ref-variables: extend PERSISTENT_DIR doc

Extend the current documentation of PERSISTENT_DIR:

- Mention that it also contains the hash equivalence database when
  BB_HASHSERVE = auto.
- Mention that it should not be shared between builds.

[YOCTO #15727]

(Bitbake rev: 682c2dccb67a57ecbf93aac8e9deea88bff10155)

Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst
index d091334a44..734c7858a2 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-ref-variables.rst
@@ -1329,8 +1329,13 @@ overview of their function and contents.
    :term:`PERSISTENT_DIR`
       Specifies the directory BitBake uses to store data that should be
       preserved between builds. In particular, the data stored is the data
-      that uses BitBake's persistent data API and the data used by the PR
-      Server and PR Service.
+      that uses BitBake's persistent data API, the data used by the PR
+      Server and PR Service, and the default location of the Hash Equivalence
+      database (when :term:`BB_HASHSERVE` is set to ``auto``).
+
+      This directory should not be shared between different builds. If you need
+      to share the Hash Equivalence database, you should setup a Hash
+      Equivalence server instead.
 
    :term:`PF`
       Specifies the recipe or package name and includes all version and