[PATCH v2 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>
Signed-off-by: Baurzhan Ismagulov <ibr@ilbers.de>
---
 doc/user_manual.md | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/doc/user_manual.md b/doc/user_manual.md
index ebc31c6..680ef9b 100644
--- a/doc/user_manual.md
+++ b/doc/user_manual.md
@@ -728,6 +728,16 @@ Cache upstream debian packages to reduce time for further downloads and to be ab
 
 ### Solution
 
+ - Signing of local repo (optional)
+
+By default, the local caching repo is not gpg signed. If you want to share it in a trusted way, you may sign it.
+To do that, install `gpg` in your build environment, import the public and private keys,
+and provide the path to the public key in `conf/local.conf`, e.g.:
+
+```
+BASE_REPO_KEY = "file://<absolute_path_to_your_pub_key_file>"'
+```
+
  - Trigger creation of local apt caching Debian packages during image generation.
 
 ```
@@ -755,5 +765,4 @@ bitbake multiconfig:qemuarm-stretch:isar-image-base
 
 ### Limitation
 
-So far the local base-apt repo is not gpg signed.
 Files fetched with the `SRC_URI` protocol "apt://" are not yet cached.
-- 
2.11.0