Gave up waiting for root device, ubuntu--vg-root doesnt exist

Question

today I installed Ubuntu 64-bit on a netbook. When the netbook boots this, error report appeared. I think there is a problem with the partitions.

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.1.21.1 (Ubuntu 1:1.21.1-1ubuntu1) built-in shell (ash)   
Enter 'help' for list of built-in commands.  

(initramfs)

Output of lsblk as requested:

$ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 232.9G  0 disk 
├─sda1   8:1    0   231G  0 part 
├─sda2   8:2    0     1K  0 part 
└─sda5   8:5    0     2G  0 part [SWAP]
sr0     11:0    1   1.2G  0 rom  /cdrom
loop0    7:0    0   1.1G  1 loop /rofs

Answer 1

Please add the outputs of lsblk -fs, fdisk /dev/sda with p flag and the report of grub repair to the question as pastebin links.

Based on searching, there seems to be similar questions on Ask Ubuntu that has no answer up to date here and Here one answer is given which explains about raid and ubuntu.

There seems to be several suggestions, some of which seem to work for some people.

1. From the initframs prompt try typing ls /dev/mapper and see if your root volume is listed. If it is not listed, try waiting 10 seconds and run ls again.

   If it is now listed, type exit and it should now find the root device and boot (taken from here

2. Edit the boot config by pressing e when grub alert to choose OS, and replace root=UUID-6500... by root=/dev/sdx where sdx is the boot partition. The problem here seems to be that the UUID is either wrong, or /dev/disk/by-UUID... does not exist(1)

3. Adding the parameter all_generic_ide to the end of the boot-line like kernel /boot/vmlinuz-2.6.27-7-generic root=UUID=43206294-74ef-434d-aca2-db74b4257590 ro quiet splash all_generic_ide seems to work for some people (2)
4. The Super User question here, seems to suggest the error is due to LVM. The solution is also given in the same which is to install lvm2.
5. The same Super User site also suggests booting using an older Kernel, if available. It seems to work for some people. Trying to boot using the Recovery option might work for some people
6. Post by nux_man777 here seems to suggest the error may be in the installation medium.

7. The error /dev/mapper/ubuntu-vg-root seems to be related to raid as described here.

   "In the installer summary screen right before the copy process starts, click the Advanced button. Change the boot partition (this is the MSDOS-style "parent" partition not the Linux partitions) to /dev/mapper/pdc_feddabdf (or whatever dmraid lists as your fakeraid partition) Make sure the checkbox is clicked to boot from this disk. note that the installer will modify grub2 to point to the correct logical partition /dev/mapper/pdc_feddabdf1 or whatever / is on."

   Detailed instructions regarding installation is given in the referred site. Please check there for more info on installation of grub.

8. Booting into a live installation media and updating ubuntu by changing root using chroot seems to work for some people (suggested by cpttripzz here). Instruction regarding chroot is here. You can also refer to this question at Unix & Linux. More details can be found at Arch Wiki and Gentoo Wiki.
9. Changing the SATA Controller to Native IDE from RAID and doing a fresh install seems to work for some people here and here
10. IDE cable or the hard disk may be bad (the same ubuntu forum as above page 40)

Answer 2

Try the following:

(initramfs) reboot

Then, at the OS chooser prompt, try booting with an older kernel.

If you succeed, then probably this will fix the problem, as suggested in @One Face's bullets 4 and 5, and the link it refers:

sudo apt-get install lvm2

Answer 3

vgchange -ay
exit

worked for me to boot into the system. it's not a permanent solution though.