Because of a hardware failure my motherboard has just been replaced. After the replacement, my system (Ubuntu 17.10) doesn't boot:

ALERT! UUID=dd84f4b3-d5bf-42e4-9b5e-ec685a461fad does not exist. Dropping to a shell.

I've used a Live USB Ubuntu to debug this problem. Here are some results:

/etc/fstab

# /etc/fstab: static file system information.## Use 'blkid' to print the universally unique identifier for a# device; this may be used with UUID= as a more robust way to name devices# that works even if disks are added and removed. See fstab(5).## <file system> <mount point>   <type>  <options>       <dump>  <pass># / was on /dev/nvme0n1p3 during installationUUID=dd84f4b3-d5bf-42e4-9b5e-ec685a461fad /               ext4    errors=remount-ro 0       1# /boot/efi was on /dev/nvme0n1p1 during installationUUID=B38D-559B  /boot/efi       vfat    umask=0077      0       1# swap was on /dev/nvme0n1p4 during installationUUID=f4134c38-10b9-478f-b550-54650a9f5140 none            swap    sw              0       0

blkid

/dev/nvme0n1p1: SEC_TYPE="msdos" UUID="B38D-559B" TYPE="vfat" PARTLABEL="EFI System Partition" PARTUUID="98be6c97-c354-49a6-a432-9201d56a421b"/dev/nvme0n1p2: LABEL="OS" UUID="B39E-7035" TYPE="vfat" PARTLABEL="fat32" PARTUUID="d3006358-8d82-4e0b-99f8-87a5261cf7e8"/dev/nvme0n1p3: LABEL="UBUNTU" UUID="dd84f4b3-d5bf-42e4-9b5e-ec685a461fad" TYPE="ext4" PARTUUID="24e5b96d-f20c-43dd-9e48-672760b0e6f7"/dev/sda1: LABEL="UBUNTU 17_1" UUID="88D4-322D" TYPE="vfat" PARTUUID="3d0a270b-01"

fdisk -l

Disk /dev/loop0: 1.3 GiB, 1427259392 bytes, 2787616 sectorsUnits: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk /dev/nvme0n1: 477 GiB, 512110190592 bytes, 1000215216 sectorsUnits: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisklabel type: gptDisk identifier: 43E35EBE-2A73-404A-9D4A-851815F33F9ADevice             Start        End   Sectors   Size Type/dev/nvme0n1p1        34     488281    488248 238.4M EFI System/dev/nvme0n1p2    488282    5934980   5446699   2.6G Microsoft basic data/dev/nvme0n1p3   5935104  933576703 927641600 442.3G Linux filesystem/dev/nvme0n1p4 933576704 1000214527  66637824  31.8G Linux swapDisk /dev/sda: 28.7 GiB, 30752636928 bytes, 60063744 sectorsUnits: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisklabel type: dosDisk identifier: 0x3d0a270bDevice     Boot Start      End  Sectors  Size Id Type/dev/sda1  *     2048 60063743 60061696 28.7G  c W95 FAT32 (LBA)

It looks like the UUID's in fstab are correct, but I still get that error message.

How can I repair my Ubuntu installation?

I've tried the given solution in ALERT! /dev/disk/by-uuid/xxxxxxxxx does not exist. Dropping to a shell, but unfortunately that didn't help (I mounted /dev/nvme0n1p3). Still the same problem.

Update:When I select UEFI boot mode in system setup, I still get this problem. But when I select legacy boot I got 'no boot device found'. But here comes the tricky part: when I select legacy mode and use F12 to select UEFI/Ubuntu, it starts without a problem.