Mount the partition containing the OS installation. For another way to fix your boot-related issues, read How to Use fsck Command. Introduction The GRUB Grand Unified Bootloader is a tool for booting and loading operating system kernels and the default bootloader for systems based on the Linux kernel. Was this article helpful? Marko Aleksic. His innate curiosity regarding all things IT, combined with over a decade long background in writing, teaching and working in IT-related fields, led him to technical writing, where he has an opportunity to employ his skills and make technology less daunting to everyone.
Next you should read. Security SysAdmin. In this step-by-step guide, you will learn how to build and compile a Linux kernel from scratch, for disabling drivers or trying experimental patches.
The order of the options is not important. This command shows current network configuration, if no option is specified. Command: partnew part type from to Create a new primary partition. Command: parttype part type Change the type of an existing partition. If the password passwd is entered, it loads the new-config-file as a new config file and restarts the GRUB Stage 2, if new-config-file is specified.
Otherwise, GRUB will just unlock the privileged instructions. You can also use this command in the script section, in which case it will ask for the password, before continueing. Data bits must be in the range and stop bits are 1 or 2.
Default is 8 data bits and one stop bit. This command is only available if GRUB is compiled with serial support. If no argument is specified, reset key mappings. Note that this command does not exchange the keys. If you want to exchange the keys, run this command again with the arguments exchanged, like this:.
This table describes to which character each of the symbols corresponds:. If neither are specified, the current setting is reported. Command: tftpserver ipaddr Caution: This command exists only for backward compatibility.
Command: unhide partition Unhide the partition partition by clearing the hidden bit in its partition type code. This is useful only when booting DOS or Windows and multiple primary partitions exist in one disk. These commands are usable in the command-line and in menu entries.
Command: blocklist file Print the block list notation of the file file. See section How to specify block lists. Only necessary if running the fully interactive command-line it is implicit at the end of a menu entry.
Command: cat file Display the contents of the file file. This command may be useful to remind you of your OS's root partition:. Command: cmp file1 file2 Compare the file file1 with the file file2. If they differ in size, print the sizes like this:. Command: configfile file Load file as a configuration file. Command: debug Toggle debug mode by default it is off. In fdisk or gdisk create a new partition starting at sector 34 and spanning to and set the type.
To have the viewable partitions begin at the base consider adding this partition last. It is advisable to use a partitioning tool that supports 1 MiB partition alignment to obtain this space as well as to satisfy other nonbyte-sector issues which are unrelated to embedding of core. Install the grub package. It will replace grub-legacy AUR if that is already installed.
Then do:. See Device file Block device names for a description of the block device naming scheme. Now you must generate the main configuration file.
Note that grub-install also tries to create an entry in the firmware boot manager , named GRUB in the above example — this will, however, fail if your boot entries are full; use efibootmgr to remove unnecessary entries.
Remember to Generate the main configuration file after finalizing the configuration. See UEFI troubleshooting in case of problems. You can follow Generated grub. If you have not done additional configuration, the automatic generation will determine the root filesystem of the system to boot for the configuration file.
For that to succeed it is important that the system is either booted or chrooted into. By default the generation scripts automatically add menu entries for all installed Arch Linux kernels to the generated configuration.
To automatically add entries for other installed operating systems, see Detecting other operating systems. See Boot menu entry examples for custom menu entry examples. To have grub-mkconfig search for other installed systems and automatically add them to the menu, install the os-prober package and mount the partitions from which the other systems boot.
Then re-run grub-mkconfig. Run os-prober as root to detect and generate an entry for it. This article or section is out of date. The two are appended to each other and passed to kernel when generating regular boot entries. It is not necessary to use both, but can be useful. This would generate a recovery boot entry without the resume and without quiet suppressing kernel messages during a boot from that menu entry.
Though, the other regular menu entries would have them as options. By default grub-mkconfig determines the UUID of the root filesystem for the configuration. See Kernel parameters for more info.
This article or section is a candidate for merging with Installation. You need to load GRUB modules mdraid09 or mdraid1x to allow you to address the volume natively:. This is done by unlocking a LUKS blockdevice in order to read its configuration and load any initramfs and kernel from it. This option tries to solve the issue of having an unencrypted boot partition. This option is used by grub-install to generate the grub core. You can use a keyfile to avoid this.
GRUB 2. See GRUB bug Use grub-install as described in the Installation section. Create grub-pre. The output is the UUID of the encrypted partition without hyphens. This sequence of commands completes the installation of GRUB on the floppy disk. It is now bootable and will allow us to boot any other OS on our system. To see how GRUB may be used to boot a multitude of different operating systems, consider this example setup:.
Note that although GRUB and Linux are capable of dealing with installations in extended partitions, here we show a preference for using primary partitions whenever possible. Filesystems in primary partitions are often mountable by other operating systems, whereas cross-OS mounting filesystems in extended partitions is often not supported.
This system has two hard disks with six different operating systems using seven partitions. As you probably know, each OS has its own nomenclature for naming devices and partitions. You get large helpings of this alphabet soup whenever maintaining any multiboot setup.
Since GRUB also needs to be capable of loading any of these systems, it has its own OS-neutral naming conventions for referring to devices. Hard disks are all hd, floppy disks are fd, device numbering starts from zero, partition numbering starts from zero and complete device names are enclosed in parentheses. With these naming rules, the floppy disk is fd0 , the Win98 partition is hd0,0 , and GRUB recognizes the Slackware and Debian partitions respectively as hd0,1 for slackware and hd0,2 for debian.
Okay, ready to give GRUB a taste? Badda-bing, badda-boom, that postage-stamp-sized Tux appears in the upper-left corner of your screen yes, Slackware is configured to use the framebuffer device , and Linux bootstraps its jolly way into glorious being.
Another example. Reboot the system again with the GRUB floppy, and enter the following commands at the grub prompt:. Now your screen turns into a vague blue cloud, and you think you have made some horrible mistake. Then you realize it's only Windows and you remind yourself to expunge this partition one day soon.
Let's take a closer look at these examples. If the device has a filesystem recognized by GRUB that is, one of ext2fs, reiser, ffs, etc. The argument to the kernel command is the filename of the boot image relative to the device specified by the root command above.
The kernel image specified is now loaded and sent rolling down the royal road to bootdom. This method of booting loads the target OS's own boot-chain-loader rather than a kernel image of the OS. In this instance, we specified:. Next, the chainloader command will use the first sector of the partition of device hd0,0 and attempt to boot whatever it finds there. This is a common means of booting OSes that install their own boot loaders in the first sector of the partition where they are installed this is sometimes called the partition boot sector or PBR.
Finally, the makeactive command sets the active flag in the partition table for the device specified by the root command, as some operating systems, like Win98, require. The GRUB command line is easy and fun, and you should boot the different OSes on your system a few times to get the hang of it. While you are testing, be sure to keep any notes specific to getting your particular kernels successfully loaded.
This information will be useful later when you configure the menu system of GRUB to perform these command-line steps automatically. The help command will display a list of the 40 or so commands available in GRUB. Typing the name a particular command after help will produce on-line help for that particular command. The cat command can be used to view the contents of a file. This is a very handy way of pulling out system configuration information if your normal boot loader gets whacked.
Note also as you are using the GRUB command line that, like bash, up and down arrows will scroll through command history, and a tab will complete the name of a GRUB command or filename. Finally, you can call up a specific menu interface with the configfile command as in:.
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