[PATCH 3/3] doc/user_manual: Describe gpg signing of local repo

["Maxim Yu. Osipov" <mosipov@ilbers.de>]

Signed-off-by: Maxim Yu. Osipov <mosipov@ilbers.de>
---
 doc/user_manual.md | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/doc/user_manual.md b/doc/user_manual.md
index eebcaa9..c9c40ae 100644
--- a/doc/user_manual.md
+++ b/doc/user_manual.md
@@ -727,6 +727,12 @@ Cache upstream debian packages to reduce time for further downloads and to be ab
 
  - Trigger creation of local apt caching Debian packages during image generation.
 
+Note: By default the local caching repo is not gpg signed.
+If you want to sign it, `gpg` has to be installed in your host system and
+a default key pair is generated,
+set `BASE_REPO_KEY` in `conf/local.conf` to `SRC_URI` of your public key,
+f.e. 'BASE_REPO_KEY = "file://<absolute_path_to_your_pub_key_file>"'.
+
 ```
 bitbake -c cache_base_repo multiconfig:qemuarm-stretch:isar-image-base
 ```
@@ -749,7 +755,3 @@ sudo rm -rf tmp
 ```
 bitbake multiconfig:qemuarm-stretch:isar-image-base
 ```
-
-### Limitation
-
-So far the local base-apt repo is not gpg signed.
-- 
2.11.0