Hi, I'm running Debian on a test system, CSM has been disabled. if I boot the stock non-RT Debian kernel, I can use efibootmgr. When I try booting the PREEMPT_RT package (linux-image-rt-amd64) or a custom PREEMPT_RT kernel with the following config options enabled: CONFIG_EFI=y CONFIG_EFI_STUB=y # CONFIG_EFI_MIXED is not set # EFI (Extensible Firmware Interface) Support CONFIG_EFI_VARS=y CONFIG_EFI_ESRT=y CONFIG_EFI_FAKE_MEMMAP=y CONFIG_EFI_MAX_FAKE_MEM=8 CONFIG_EFI_RUNTIME_WRAPPERS=y CONFIG_EFI_BOOTLOADER_CONTROL=y # CONFIG_EFI_CAPSULE_LOADER is not set # CONFIG_EFI_TEST is not set CONFIG_EFI_PARTITION=y CONFIG_FB_EFI=y CONFIG_EFIVAR_FS=y # CONFIG_EFI_PGT_DUMP is not set CONFIG_FAT_FS=y CONFIG_VFAT_FS=y CONFIG_FAT_DEFAULT_CODEPAGE=437 CONFIG_FAT_DEFAULT_IOCHARSET="iso8859-1" CONFIG_FAT_DEFAULT_UTF8=y I get this message: EFI variables are not supported on this system. Mount and everything looks the same as it does in the non-RT kernel: /dev/sda2 on /boot/efi type vfat (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro) Adding `add_efi_memmap` to kernel params doesn't fix this either. When using a non-PREEMPT_RT kernel, everything with EFI works. Any idea? Is this a known issue with PREEMPT_RT? Alec
