docs: Add note about SandboxTrees= to SkeletonTrees=

diff --git a/mkosi/resources/man/mkosi.1.md b/mkosi/resources/man/mkosi.1.md
index ab842ec1f2059508c94bedc7bd71b45283192677..d1e6c851f4974c5914ca8036efa2226835a0641f 100644 (file)
--- a/mkosi/resources/man/mkosi.1.md
+++ b/mkosi/resources/man/mkosi.1.md
@@ -778,6 +778,13 @@ boolean argument: either `1`, `yes`, or `true` to enable, or `0`, `no`,
     file may be provided too. `mkosi.skeleton.tar` will be automatically
     used if found in the local directory.
 
+    To add extra package manager configuration files such as extra
+    repositories, use `SandboxTrees=` as mkosi invokes the package
+    managers from outside the image and not inside so any package
+    manager configuration files provided via `SkeletonTrees=` won't
+    take effect when mkosi invokes a package manager to install
+    packages.
+
 `ExtraTrees=`, `--extra-tree=`
 :   Takes a comma separated list of colon separated path pairs. The first
     path of each pair refers to a directory to copy from the host into the