Installation-instructions.md

+**Note:** to just update the image, follow the instructions from
+- [Build image (using mkosi)](#build-image-using-mkosi)
+- [Set permissions for image](#set-permissions-for-image)
+- [Start and enable xcache service running in container](#start-and-enable-xcache-service-running-in-container)
+
 # Install packages on debian host system
 ```bash
 apt install acl dnf rpm git systemd-container rsync voms-clients