when I start ubuntu every time it says unknown file system grub rescue error.
ProblemType: Package
DistroRelease: Ubuntu 14.04
Package: grub-pc 2.02~beta2-9ubuntu1.7
ProcVersionSignature: Ubuntu 3.13.0-77.121-generic 3.13.11-ckt32
Uname: Linux 3.13.0-77-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.19
Architecture: amd64
Date: Thu Jan 28 20:49:36 2016
DuplicateSignature: package:grub-pc:2.02~beta2-9ubuntu1.7:subprocess installed post-installation script returned error exit status 128
ErrorMessage: subprocess installed post-installation script returned error exit status 128
InstallationDate: Installed on 2014-10-22 (463 days ago)
InstallationMedia: Ubuntu 12.04.3 LTS "Precise Pangolin" - Release amd64 (20130820.1)
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.13.0-77-generic root=UUID=2168d211-9deb-4320-81f3-b0d94192ee68 ro quiet splash acpi_backlight=vendor
RelatedPackageVersions:
dpkg 1.17.5ubuntu5.5
apt 1.0.1ubuntu2.11
SourcePackage: grub2
Title: package grub-pc 2.02~beta2-9ubuntu1.7 failed to install/upgrade: subprocess installed post-installation script returned error exit status 128
UpgradeStatus: Upgraded to trusty on 2015-04-18 (285 days ago)
You have added two incorrect lines to the end of /etc/default/grub: you need to set those options in the existing line which is terminated with an end quote.