GRUB reports no Operating System
So, you deleted all the kernels? or possibly it's so messed up GRUB can't find it ?
root with live system
Boot from live media (the "Desktop" image), open an LXTerminal session and gain root access by typing in
sudo -i
Please remember that you have now turned off the inbuilt protection of Lubuntu, be VERY careful what you type!
identify root filesystem
Firstly, find where the Linux installation is..
fdisk -l
traditional setup
You will see something like this :
/dev/sda1 * 1 4660 37431418+ 83 Linux
/dev/sda2 4661 4865 1646662+ 5 Extended
/dev/sda5 4661 4865 1646631 82 Linux swap / SolarisLook for the entry that ends in "83 Linux" which is /dev/sda1 in the above example.
If there is also a line with "LVM" in it, then you will need to skip to the LVM section below.
GPT
If the disk you think it is has only one partition with a "GPT" system, then you'll need to use a different tool than fdisk (unless you have package util-linux v2.23+ which is available in Utopic and beyond). This indicates that the drive uses GUID Partition Table instead of Master Boot Record. The former is starting to become more and more standard. Instead of fdisk, try:
parted -l
which should give an output something like:
Model: ATA Hitachi HDS72168 (scsi) Disk /dev/sda: 80.0GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 1049kB 62.5GB 62.5GB primary ext4 2 62.5GB 71.1GB 8595MB primary linux-swap(v1)
In this case, the right partition is certainly /dev/sda1. (Please note that this example is MBR and not GPT, but the output should be similar).
LVM
If the fdisk command above yields a line like:
/dev/sda5 501760 976771071 488134656 8e Linux LVM
Then you have logical volume management, which requires a slightly different approach. You can get more information about your LVM partition with the following:
pvs
which will yield something like:
PV VG Fmt Attr PSize PFree /dev/sda5 lubuntu-vg lvm2 a-- 465.52g 52.00m
Usually with LVM your normal partitions are contained within volume groups, which is what the "VG" column refers to. The kernel usually maps these to /dev/<VG>, so in this case, that would be /dev/lubuntu-vg. You can find out more specific information about your volume group:
lvdisplay /dev/<VG>
which should include output like so:
--- Logical volume --- LV Path /dev/lubuntu-vg/root LV Name root
You need to identify your root file system, which in this case is clearly /dev/lubuntu-vg/root.
mount filesystem
Next, mount the partition in terms of the device file as per what was reported above, e.g. /dev/sda1, /dev/lubuntu-vg/root, etc.
mount <device file> /mnt
/mnt can also be some other directory (that must exist), should you choose.
Internet access
Use nm-applet to get connected to your wifi or plug in your Ethernet. Then copy over resolv.conf:
cp /etc/resolv.conf /mnt/etc/resolv.conf
point local filesystem at your HDD
for fs in sys proc dev dev/pts; do mount --bind /$fs /mnt/$fs; done chroot /mnt
- At this point, if you cd /, you'll be in your hard drive rather than the root of the live desktop. That being said, be careful!
divert installation to your HDD
dpkg-divert --local --rename --add /sbin/init ln -s /bin/true /sbin/init
install the kernel
apt-get install linux-image-generic
Be aware that if you use a different kernel than the standard one, such as low-latency, you should install the appropriate package, which you can list with: apt-cache search linux-image-.
If you have an error with the install, such as:
P: Installing debian theme...cp: cannot stat ‘/usr/share/syslinux/themes/debian-wheezy/extlinu/memtest.bin’: No such file or directory
then chances are you booted into memtest. For some reason you get an error that the file does not exist when it does. If you remove it, problem solved. After that, you'll need to reconfigure:
dpkg --configure -a
update GRUB
Next, you need to tell GRUB to update grub.cfg to allow you to use the new kernel.
update-grub
LVM concerns
A typical LVM setup puts /boot in a separate partition not managed by LVM. This means updating GRUB can only affect the /boot on the logical volume.
You could mount the separate partition, but you can't chroot to it since this command always runs some command (default is /bin/sh) and no commands exist on the partition.
However, when you update GRUB, you load the necessary modules to load the kernel and initial ramdisk from the logical volume. So if you copy /boot from the logical volume to the separate partition, you'll be good to go!
To do this:
Follow the clean up instructions below. No, you don't need to be in the chroot anymore.
Mount both filesystems. You should have the logical volume already mounted so just go here to identify the separate partition and mount it.
- Make a backup of the original boot:
### The following example assumes: ### * Your logical volume is mounted to /mnt/root ### * Your separate partition is mounted to /mnt/boot mkdir /mnt/root/oldgrub mv /mnt/boot/* /mnt/root/oldgrub
- Copy over the new boot:
### See the previous for assumptions on this example cp -R /mnt/root/grub/* /mnt/boot/
- Reboot and enjoy your new kernel! To be sure all is well, make sure to update GRUB once again:
update-grub
clean up
Remove the link and divert...
unlink /sbin/init dpkg-divert --rename --remove /sbin/init exit
https://help.ubuntu.com/community/Grub2/Installing#Reinstalling_GRUB_2 All done!! Restart you will have the option to boot into the new kernel. If for some reason, it doesn't boot right in, hold down SHIFT when your system starts up to see the GRUB menu.
still problems…
If you have come here for an edge case and/or not found luck, you may want to consider reinstalling GRUB.