@sebastian-roth Hi ! the initial kernel bzimage after fresh install was 4.11.0. I attempted to update from web interface but it was tricky because of rights on directories. Finally, I did it (command line via putty) but the pxe boot resulted in an error. I worked again on it and I succeeded : the current version is now 4.13.4 and all is working great ! I had to copy this new kernel in two places : /var/www/html/fog/service/ipxe and /var/www/fog/service/ipxe to overcome an error during the pxe boot process. That said, we configured another fog server for redundancy purpose and the upgrade from web interface 4.11.0 to 4.13.4 worked perfectly this time …(?) Thanks to every body for the reactivity. The Fog server is our very useful weekly tool to restore our classrooms… Best regards.