Suddenly my Ubuntu 16.04 drops me into an initramfs prompt like this:BusyBox v.1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)   Enter 'help' for list of built-in commands.  (initramfs)If I type exit I get:Gave up waiting for root device. Common problems:   Boot args (cat /proc/cmdline)     Check rootdelay= (did the system wait long enough?)     Check root= (did the system wait for the right device?)   Missing modules (cat /proc/modules; ls /dev)ALERT! /dev/mapper/ubuntu--vg-root does not exist. Dropping to a shell!BusyBox v.1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)   Enter 'help' for list of built-in commands. (initramfs)Things I've tried, without success so far:Tried recovering a superblock backup with a USB boot disk, still boots into this.Cannot boot into a different kernel because when pressing SHIFT at grub time I only get one kernel in the advanced options.When I get at the grub screen, if I press e these are my settings:setparams 'Ubuntu'    recordfail    load_video    gfxmode $linux_gfx_mode    insmod gzio    if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi    insmod part_msdos    insmod ext2    set root='hd0,msdos1'    if [ x$feature_platform_search_hint = xy ]; then      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 7ec61194-f216-4f1b-b684-5b2e2d643c25    else      search --no-floppy --fs-uuid --set=root 7ec61194-f216-4f1b-b684-5b2e2d643c25    fi    linux        /vmlinux-4.4.0-24-generic root=/dev/mapper/ubuntu--vg-root ro  quiet splash $vt_handoff    initrd         /initrd.img-4.4.0-24-genericIf I boot into a bootable LIVE usb disk sudo fdisk -l returns:Disk /dev/sda: 480.1 GB, 480103981056 bytes255 heads, 63 sectors/track, 58369 cylinders, total 937703088 sectorsUnits = sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk identifier: 0x60229a0a   Device  Boot     Start       End     Blocks    Id   System/dev/sda1    *       2048    999423     498688    83   Linux/dev/sda2         1001470 937701375  468349953     5   Extended/dev/sda5         1001472 937701375  468349952    83   LinuxDisk /dev/sdb: (skipping since I think this is the USB disk...)If I mount the partitions via nautilus (the encrypted one prompts me for my password, which I enter), then sudo lsblk returns:NAME                                                 MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTsda                                                    8:0    0 447.1G  0 disksda1                                                 8:1    0   487M  0 part /media/ubuntu/7ec61194-f216-4f1b-b684-5b2e2d643csda2                                                 8:2    0     1K  0 partsda5                                                 8:5    0 446.7G  0 part  luks-11613ca4-65f2-4079-a750-6f71b6318903 (dm-0) 252:0    0 446.7G  0 crypt    ubuntu--vg-root (dm-1)                         252:1    0 439.2G  0 lvm    ubuntu--vg-swap_1 (dm-2)                       252:2    0   7.5G  0 lvmsdb                                                    8:16   1   1.9G  0 disksdb1                                                 8:17   1   1.9G  0 part /cdromsr0                                                   11:0    1  1024M  0 romloop0                                                  7:0    0 938.7M  1 loopWhat's wrong? What is preventing the system to boot up and ask me the encryption password like usual? Thanks!
Ubuntu 16.04 stops booting, it has LVM and LUKS encryption configured, superblock restore already tried
ubuntu;grub2;lvm;luks;initramfs