Alternatively, you can reach the GRUB command line during bootup. Let's say you have installed yet another operating system on your machine, Sabayon. During the installation, you skip the GRUB setup. This means that the original GRUB remains untouched - and it does not contain an entry about Sabayon. For all practical purposes, Sabayon is not bootable.
Note: GRUB menu entries are called stanzas probably a twist of instance? So, we need to add Sabayon to the list. If you know where Sabayon is installed, you just need to add its entry to the menu.
You can also do this while booting the computer, without editing the menu. And then:. Optionally, you will use the find command to get around.
Basically, this is the whole of GRUB magic. As you can see, it's very very simple. But for people who have never heard of GRUB and see long lists of strange commands, the prospect can be daunting. Now that we have covered the basics of grubbing, it's time for extras and some more common problems. This will often happen if you install Windows after Linux.
Windows assumes it's the only operating system in the world and does not try to live with existing information present in the MBR; it overwrites it. For people with dual-boot and very little knowledge of Linux, this is a disaster.
Luckily, it's very easily recoverable one. Use Super Grub Disk. I have written about this tool in detail in my article A cool list of Linux tools , under Rescue. GRUB cannot directly boot Microsoft operating systems. And sometimes, even chainloading may not work, especially if Windows is not installed on the first hard disk. Once again, you should remember that you should always install Windows first, on the first hard disk, on the first partition the rule of three first.
Nevertheless, even if you have Windows installed on a separate disk, you can solve the problem by swapping. You need to perform a virtual swap between hard disks. Like this:. After you add these two lines, you should be able to boot into Windows or DOS, for that matter. Again, Windows can cause problems if there's more than one instance present on a hard disk, especially if installed on primary partitions.
When you use the chainloader command, the control is transferred to the Windows boot loader, but which one? The problem is easily solved by hiding and unhiding partitions. Vice versa, if you unhide a partition, Windows will detect it and be able to boot from it, without getting confused. Here's the example taken from the Manual that demonstrates this point. Let's say we have Windows installed on the first and the second partition of your hard disk.
We wish to boot the first instance of Windows. Then, we need to execute the following set of commands to make it all work:. This is an interesting case. It can happen after you use a partitioning or an imaging software to make changes to the Partition Table.
Usually, this will happen when you make such a change in Windows. Linux will not be informed of the change, because Windows is blind to anything else on the machine save Microsoft thingies. Consequently, GRUB will suffer. The solution is that most likely the filesystem is damaged and needs to be repaired.
Boot from a live CD and execute the following commands, assuming you know where Linux partitions are. Check the filesystem:. Replace X and Y with hard disk letter and partition number that you want to check hda2, hdb3, etc.
You're back to the familiar grounds. For more information on Linux commands, including fsck. Finally, some more tricky questions answered in Ubuntu wiki :. How to identify the name of the boot drive hd0, hd1, hd2, etc.
GParted is a Gnome Partition Editor. It runs from a CD. This is a live CD specifically geared toward rescue and recovery. The tools package includes some of the most important tools available for Linux user, like GParted, QTParted, Partimage, Grub, Lilo, sfdisk, security tools, network tools, and more. Super Grub Disk is intended to run from a floppy disk or CD and is used for system rescue.
TestDisk is a utility specially designed to recover lost partitions and make non-booting disks bootable again. How To Multi-boot Operating Systems. How to boot Ubuntu from the Windows Bootloader. Filesystems and Mounting.
The list of command line and menu entry commands. If you find this article useful, please support Dedoimedo! This tutorial focuses on GRUB legacy. If you're looking for a tutorial on GRUB 2, the next generation of the popular bootloader, please take a look at this article.
You may also like:. The vm part is a hark back to when virtual memory support was a big thing, and slapping vm at the front told everyone that the system supported virtual memory, and then the z or the zed at the end tells us that the kernel image is a compressed image, which keeps it small. So, this initrd file gets loaded into memory as a temporary root file system hence the name RAM disk, and then the kernel uses it to access and load modules that are needed to do other things in the boot process.
The second thing right about initrd is that initrd is sort of a legacy term for it because these days, at least since the 2. We have gotten initramfs matching our kernel version and architecture, and that is how GRUB is configured to boot Linux.
These will be listed here as well in the same way. Reads grub. You may also have a look at the following articles to learn more —. Submit Next Question.
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Popular Course in this category. Course Price View Course. Free Software Development Course. Login details for this Free course will be emailed to you. Email ID. Contact No. Use the set command with no arguments to view the environment variables :.
The example output shows that GRUB is set up to boot from hd0,msdos3 partition:. The ls command lists the available partitions on the disk. Use the ls command to find the partition containing the boot directory.
The example shows the boot directory in the hd0,msdos1 partition. Set the boot partition as the value of the root variable. The example uses the partition named hd0,msdos1.
Another way to fix your GRUB boot issues is to use a Linux live image to boot from an external device. Open the terminal and type the following command to add the repository for the Boot Repair tool. Note : The Boot Repair tool is available as a live image , so you can boot it from an external drive without using another live OS.
Mount the partition containing the OS installation. For another way to fix your boot-related issues, read How to Use fsck Command.
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