I have removed my MBR by mistake. Now I can't boot Ubuntu, so I want to reinstall grub.I'm getting this error:grub-install --boot-directory=/media/cab64688-2d97-4bbd-9f32-7bc0badb40a8/boot /dev/sdbrm: cannot remove `/media/cab64688-2d97-4bbd-9f32-7bc0badb40a8/boot/grub/915resolution.mod': Read-only file systemSo, the problem is that my existing Ubuntu partition is mounted read only. When I try:sudo mount /dev/sdb7  /media/ubuntu_mptmount: block device /dev/sdb7 is write-protected, mounting read-onlySo I failed to install grub since I'm in read only mode.Any ideas?EDIT: After apt-get install grub, I repeated the process and got:Probing devices to guess BIOS drives. This may take a long time.Unknown partition table signaturesed: can't read /media/cab64688-2d97-4bbd-9f32-7bc0badb40a8_/boot/grub/device.map: No such file or directorygrep: /media/cab64688-2d97-4bbd-9f32-7bc0badb40a8_/boot/grub/device.map: No such file or directory/dev/sda does not have any corresponding BIOS drive.
grub-install from live CD
grub
$ sudo mount /dev/sdb7  /media/ubuntu_mptThis should be:$ sudo mount -o remount,rw /dev/sdb7This will not mount it again, but change the already existing mount to rw.