Installation-instructions.md

@@ -45,7 +45,7 @@ build_image.sh /var/lib/machines/$img_name
 ```
 
 # Create xrootd user in host system
-We will map the xrootd user id inside the container (typically 999) to one shifted by 65536 * 10 on the host system. This is an arbitrary choice and one should check this range of user ids is not used by anything else.
+We will map the xrootd user id inside the container (typically 999) to one shifted by 65536 * 10 on the host system. This is an arbitrary choice and one should check this range of user ids is not used by anything else. Problem with this: what if we create a new image and for some reason xrootd ends up being a different user - then it won't be correct anymore for this image. One solution would be to force the user id inside the container to be a fixed one during image building ...
 ```bash
 # for some reason that command might add a carriage return (therefore the sed) ...
 XRD_UID_INSIDE=$(systemd-nspawn -D /var/lib/machines/$img_name id -u xrootd | sed 's/\r//')