Hi, I am using Buster and start the computer in BIOS mode. After installing the security updates of grub2 (4 files; 2.02+dfsg1-20+deb10u4) the computer didn't boot any more and I got the same error message as described in bug #984520.
With the help of Super Grub 2.02 I could start the laptop and reinstalled old grub2 (4 files; 2.02+dfsg1-20+deb10u3). Then it booted as usual. Afterwards I installed grub-rescue-pc (2.02+dfsg1-20+deb10u4) and burned the image on CD. I tried to boot the PC with this CD but it failed with: mounting /dev on /root/dev failed: not such file or directory and several more error messages. What made me warily was the fact that only sda has been mounted. On sda grub is not installed on my computer. I installed it on sdb. So it could not find the boot files and booting failed. sudo debconf-show grub-pc * grub2/linux_cmdline_default: quiet grub2/kfreebsd_cmdline: grub-pc/hidden_timeout: false grub-pc/disk_description: grub-pc/kopt_extracted: false grub-pc/postrm_purge_boot_grub: false grub2/device_map_regenerated: grub-pc/install_devices_disks_changed: grub-pc/chainload_from_menu.lst: true grub-pc/install_devices_failed: false * grub2/linux_cmdline: grub-pc/timeout: 5 grub2/update_nvram: true grub-pc/mixed_legacy_and_grub2: true grub2/force_efi_extra_removable: false grub-pc/install_devices_empty: false grub2/kfreebsd_cmdline_default: quiet * grub-pc/install_devices: /dev/disk/by-id/ata-WDC_WD10JPVX-60JC3T0_WD- WX71A858X5KH grub-pc/install_devices_failed_upgrade: true grub-pc/partition_description: ls -l /dev/disk/by-id/ insgesamt 0 lrwxrwxrwx 1 root root 9 Mär 5 16:38 ata-hp_DVDRW_SU208GB_S16F6YIG901G9X -> ../../sr0 lrwxrwxrwx 1 root root 9 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K -> ../../sdb lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K-part1 -> ../../sdb1 lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K-part2 -> ../../sdb2 lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K-part3 -> ../../sdb3 lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K-part5 -> ../../sdb5 lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K-part6 -> ../../sdb6 lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-Samsung_SSD_860_EVO_M. 2_500GB_S414NB0K906860K-part7 -> ../../sdb7 lrwxrwxrwx 1 root root 9 Mär 5 16:38 ata-WDC_WD10JPVX-60JC3T0_WD- WX71A858X5KH -> ../../sda lrwxrwxrwx 1 root root 10 Mär 5 16:38 ata-WDC_WD10JPVX-60JC3T0_WD- WX71A858X5KH-part1 -> ../../sda1 lrwxrwxrwx 1 root root 9 Mär 5 16:38 wwn-0x50014ee60612880e -> ../../sda lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x50014ee60612880e-part1 -> ../../ sda1 lrwxrwxrwx 1 root root 9 Mär 5 16:38 wwn-0x5002538e407c123b -> ../../sdb lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x5002538e407c123b-part1 -> ../../ sdb1 lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x5002538e407c123b-part2 -> ../../ sdb2 lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x5002538e407c123b-part3 -> ../../ sdb3 lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x5002538e407c123b-part5 -> ../../ sdb5 lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x5002538e407c123b-part6 -> ../../ sdb6 lrwxrwxrwx 1 root root 10 Mär 5 16:38 wwn-0x5002538e407c123b-part7 -> ../../ sdb7 Regards Dieter