6.1 2008-05-02
Making your Choice Introduction

Now that your kernel is configured and compiled and the necessary system configuration files are filled in correctly, it is time to install a program that will fire up your kernel when you start the system. Such a program is called a bootloader.

For , Gentoo Linux provides GRUB and LILO.

Using LILO on the AMD64 architecture is not recommended.

But before we install the bootloader, we inform you how to configure framebuffer (assuming you want it of course). With framebuffer you can run the Linux command line with (limited) graphical features (such as using the nice bootsplash image Gentoo provides).

Optional: Framebuffer

If you have configured your kernel with framebuffer support (or you used genkernel default kernel configuration), you can activate it by adding a vga and/or a video statement to your bootloader configuration file.

First of all, you need to know what type of framebuffer device you're using. If you use a Gentoo patched kernel tree (such as gentoo-sources) you will have had the possibility of selecting uvesafb as the VESA driver. If this is the case, you are using uvesafb and do not need to set a vga statement. Otherwise you are using the vesafb driver and need to set the vga statement.

The vga statement controls the resolution and color depth of your framebuffer screen for vesafb. As stated in /usr/src/linux/Documentation/fb/vesafb.txt (which gets installed when you install a kernel source package), you need to pass the VESA number corresponding to the requested resolution and color depth to it.

The following table lists the available resolutions and color depths and matches those against the value that you need to pass on to the vga statement.

0x3010x3030x3050x3070x3100x3130x3160x3190x3110x3140x3170x31A0x3120x3150x3180x31B
640x480 800x600 1024x768 1280x1024
256
32k
64k
16M

The video statement controls framebuffer display options. It needs to be given the framebuffer driver followed by the control statements you wish to enable. All variables are listed in /usr/src/linux/Documentation/fb/vesafb.txt. The most-used options are:

ywrap Assume that the graphical card can wrap around its memory (i.e. continue at the beginning when it has approached the end) mtrr:n Setup MTRR registers. n can be:
0 - disabled
1 - uncachable
2 - write-back
3 - write-combining
4 - write-through mode (uvesafb only)
Set up the resolution, color depth and refresh rate. For instance, 1024x768-32@85 for a resolution of 1024x768, 32 bit color depth and a refresh rate of 85 Hz.
Control Description

The result of those two statements could be something like vga=0x318 video=vesafb:mtrr:3,ywrap or video=uvesafb:mtrr:3,ywrap,1024x768-32@85. Write this setting down; you will need it shortly.

Now, you should install the elilo bootloader.

Now continue by installing GRUB or LILO.

Default: Using GRUB Understanding GRUB's terminology

The most critical part of understanding GRUB is getting comfortable with how GRUB refers to hard drives and partitions. Your Linux partition /dev/sda1 will most likely be called (hd0,0) under GRUB. Notice the parentheses around the hd0,0 - they are required.

Hard drives count from zero rather than "a" and partitions start at zero rather than one. Be aware too that with the hd devices, only hard drives are counted, not atapi-ide devices such as cdrom players and burners. Also, the same construct is used with SCSI drives. (Normally they get higher numbers than IDE drives except when the BIOS is configured to boot from SCSI devices.) When you ask the BIOS to boot from a different hard disk (for instance your primary slave), that harddisk is seen as hd0.

Assuming you have a hard drive on /dev/sda and two more on /dev/sdb and /dev/sdc, /dev/sdb7 gets translated to (hd1,6). It might sound tricky and tricky it is indeed, but as we will see, GRUB offers a tab completion mechanism that comes handy for those of you having a lot of hard drives and partitions and who are a little lost in the GRUB numbering scheme.

Having gotten the feel for that, it is time to install GRUB.

Installing GRUB

To install GRUB, let's first emerge it:

If you are using a non-multilib profile, you should not emerge grub, but instead you should emerge grub-static. 
# emerge grub

Although GRUB is now installed, we still need to write up a configuration file for it and place GRUB in our MBR so that GRUB automatically boots your newly created kernel. Create /boot/grub/grub.conf with nano (or, if applicable, another editor): 

# nano -w /boot/grub/grub.conf

Now we are going to write up a grub.conf. Below you'll find two possible grub.conf for the partitioning example we use in this guide. We've only extensively commented the first grub.conf. Make sure you use your kernel image filename and, if appropriate, your initrd image filename.

  • The first grub.conf is for people who have not used genkernel to build their kernel
  • The second grub.conf is for people who have used genkernel to build their kernel
If your root filesystem is JFS, you must add " ro" to the kernel line since JFS needs to replay its log before it allows read-write mounting. 
# Which listing to boot as default. 0 is the first, 1 the second etc.
default 0
# How many seconds to wait before the default listing is booted.
timeout 30
# Nice, fat splash-image to spice things up :)
# Comment out if you don't have a graphics card installed
splashimage=(hd0,0)/boot/grub/splash.xpm.gz

title Gentoo Linux 
# Partition where the kernel image (or operating system) is located
root (hd0,0)
kernel /boot/ root=/dev/sda3

title Gentoo Linux  (rescue)
# Partition where the kernel image (or operating system) is located
root (hd0,0)
kernel /boot/ root=/dev/sda3 init=/bin/bb

# The next four lines are only if you dualboot with a Windows system.
# In this case, Windows is hosted on /dev/sda6.
title Windows XP
rootnoverify (hd0,5)
makeactive
chainloader +1

default 0
timeout 30
splashimage=(hd0,0)/boot/grub/splash.xpm.gz

title Gentoo Linux 
root (hd0,0)
kernel /boot/ root=/dev/ram0 init=/linuxrc ramdisk=8192 real_root=/dev/sda3 udev
initrd /boot/

# Only in case you want to dual-boot
title Windows XP
rootnoverify (hd0,5)
makeactive
chainloader +1
The udev mentioned at the end of the kernel line is needed to work around a bug in some genkernel versions if you use udev in the first place (which is the default behaviour).

If you used a different partitioning scheme and/or kernel image, adjust accordingly. However, make sure that anything that follows a GRUB-device (such as (hd0,0)) is relative to the mountpoint, not the root. In other words, (hd0,0)/grub/splash.xpm.gz is in reality /boot/grub/splash.xpm.gz since (hd0,0) is /boot.

Besides, if you chose to use a different partitioning scheme and did not put /boot in a separate partition, the /boot prefix used in the above code samples is really required. If you followed our suggested partitioning plan, the /boot prefix it not required, but a boot symlink makes it work. In short, the above examples should work whether you defined a separate /boot partition or not.

If you need to pass any additional options to the kernel, simply add them to the end of the kernel command. We're already passing one option (root=/dev/sda3 or real_root=/dev/sda3), but you can pass others as well, such as the video and/or vga statements for framebuffer as we discussed previously.

If you're using a 2.6.7 or higher kernel and you jumpered your harddrive because the BIOS can't handle large harddrives you'll need to append sda=stroke. Replace sda with the device that requires this option.

genkernel users should know that their kernels use the same boot options as is used for the Installation CD. For instance, if you have SCSI devices, you should add doscsi as kernel option.

Now save the grub.conf file and exit. You still need to install GRUB in the MBR (Master Boot Record) so that GRUB is automatically executed when you boot your system.

The GRUB developers recommend the use of grub-install. However, if for some reason grub-install fails to work correctly you still have the option to manually install GRUB.

Continue with Default: Setting up GRUB using grub-install or Alternative: Setting up GRUB using manual instructions.

Default: Setting up GRUB using grub-install

To install GRUB you will need to issue the grub-install command. However, grub-install won't work off-the-shelf since we are inside a chrooted environment. We need to create /etc/mtab which lists all mounted filesystems. Fortunately, there is an easy way to accomplish this - just copy over /proc/mounts to /etc/mtab, excluding the rootfs line if you haven't created a separate boot partition. The following command will work in both cases: 

# grep -v rootfs /proc/mounts > /etc/mtab

Now we can install GRUB using grub-install: 

# grub-install --no-floppy /dev/sda

If you have more questions regarding GRUB, please consult the GRUB FAQ or the GRUB Manual.

Continue with Rebooting the System.

Alternative: Setting up GRUB using manual instructions

To start configuring GRUB, you type in grub. You'll be presented with the grub> grub command-line prompt. Now, you need to type in the right commands to install the GRUB boot record onto your hard drive. 

# grub --no-floppy
If your system does not have any floppy drives, add the --no-floppy option to the above command to prevent grub from probing the (non-existing) floppy drives.

In the example configuration we want to install GRUB so that it reads its information from the boot partition , and installs the GRUB boot record on the hard drive's MBR (master boot record) so that the first thing we see when we turn on the computer is the GRUB prompt. Of course, if you haven't followed the example configuration during the installation, change the commands accordingly.

The tab completion mechanism of GRUB can be used from within GRUB. For instance, if you type in "root (" followed by a TAB, you will be presented with a list of devices (such as hd0). If you type in "root (hd0," followed by a TAB, you will receive a list of available partitions to choose from (such as hd0,0).

By using the tab completion, setting up GRUB should be not that hard. Now go on, configure GRUB, shall we? :-) 

grub> root (hd0,0)    (Specify where your /boot partition resides)
grub> setup (hd0)     (Install GRUB in the MBR)
grub> quit            (Exit the GRUB shell)
If you want to install GRUB in a certain partition instead of the MBR, you have to alter the setup command so it points to the right partition. For instance, if you want GRUB installed in /dev/sda3, then the command becomes setup (hd0,2). Few users however want to do this.

If you have more questions regarding GRUB, please consult the GRUB FAQ or the GRUB Manual.

Continue with Rebooting the System.

Alternative: Using LILO Installing LILO Using LILO on the AMD64 architecture is not recommended.

LILO, the LInuxLOader, is the tried and true workhorse of Linux bootloaders. However, it lacks some features that GRUB has (which is also the reason why GRUB is currently gaining popularity). The reason why LILO is still used is that, on some systems, GRUB doesn't work and LILO does. Of course, it is also used because some people know LILO and want to stick with it. Either way, Gentoo supports both, and apparently you have chosen to use LILO.

Installing LILO is a breeze; just use emerge. 

# emerge lilo
Configuring LILO

To configure LILO, you must create /etc/lilo.conf. Fire up your favorite editor (in this handbook we use nano for consistency) and create the file. 

# nano -w /etc/lilo.conf

Some sections ago we have asked you to remember the kernel-image name you have created. In the next example lilo.conf we use the example partitioning scheme. There are two separate parts:

  • One for those who have not used genkernel to build their kernel
  • One for those who have used genkernel to build their kernel

Make sure you use your kernel image filename and, if appropriate, your initrd image filename.

If your root filesystem is JFS, you must add a append="ro" line after each boot item since JFS needs to replay its log before it allows read-write mounting. 
boot=/dev/sda             # Install LILO in the MBR
prompt                    # Give the user the chance to select another section
timeout=50                # Wait 5 (five) seconds before booting the default section
default=gentoo            # When the timeout has passed, boot the "gentoo" section

# For non-genkernel users
image=/boot/
  label=gentoo            # Name we give to this section
  read-only               # Start with a read-only root. Do not alter!
  root=/dev/sda3          # Location of the root filesystem

image=/boot/
  label=gentoo.rescue     # Name we give to this section
  read-only               # Start with a read-only root. Do not alter!
  root=/dev/sda3          # Location of the root filesystem
  append="init=/bin/bb"   # Launch the Gentoo static rescue shell

# For genkernel users
image=/boot/
  label=gentoo
  read-only
  root=/dev/ram0
  append="init=/linuxrc ramdisk=8192 real_root=/dev/sda3 udev"
  initrd=/boot/

# The next two lines are only if you dualboot with a Windows system.
# In this case, Windows is hosted on /dev/sda6.
other=/dev/sda6
  label=windows
The udev mentioned at the end of the append line is needed to work around a bug in some genkernel versions if you use udev in the first place (which is the default behaviour). If you use a different partitioning scheme and/or kernel image, adjust accordingly.

If you need to pass any additional options to the kernel, add an append statement to the section. As an example, we add the video statement to enable framebuffer: 

image=/boot/
  label=gentoo
  read-only
  root=/dev/sda3
  append="video=vesafb:mtrr,ywrap,1024x768-32@85"

If you're using a 2.6.7 or higher kernel and you jumpered your harddrive because the BIOS can't handle large harddrives you'll need to append sda=stroke. Replace sda with the device that requires this option.

genkernel users should know that their kernels use the same boot options as is used for the Installation CD. For instance, if you have SCSI devices, you should add doscsi as kernel option.

Now save the file and exit. To finish up, you have to run /sbin/lilo so LILO can apply the /etc/lilo.conf to your system (i.e. install itself on the disk). Keep in mind that you'll also have to run /sbin/lilo every time you install a new kernel or make any changes to the menu. 

# /sbin/lilo

If you have more questions regarding LILO, please consult its wikipedia page.

You can now continue with Rebooting the System.

Default: Installing elilo

On the IA64 platform, the boot loader is called elilo. You may need to emerge it on your machine first. 

# emerge elilo

You can find the configuration file at /etc/elilo.conf and a sample file in the typical docs dir /usr/share/doc/elilo-<ver>/. Here is another sample configuration: 

boot=/dev/sda1
delay=30
timeout=50
default=Gentoo
append="console=ttyS0,9600"
prompt

image=/vmlinuz
	label=Gentoo
	root=/dev/sda2
	read-only

image=/vmlinuz.old
	label=Gentoo.old
	root=/dev/sda2
	read-only

The boot line tells elilo the location of the boot partition (in this case, /dev/sda1). The delay line sets the number of 10th of seconds before automatically booting the default when in non-interactive mode. The timeout line is just like the delay line but for interactive mode. The default line sets the default kernel entry (which is defined below). The append line adds extra options to the kernel command line. The prompt sets the default elilo behavior to interactive.

The sections that start with image define different bootable images. Each image has a nice label, a root filesystem, and will only mount the root filesystem read-only.

When configuration is done, just run elilo --efiboot. The --efiboot option adds a menu entry for Gentoo Linux to the EFI Boot Manager. 

# elilo --efiboot

Now continue with Rebooting the System.

Rebooting the System

Exit the chrooted environment and unmount all mounted partitions. Then type in that one magical command you have been waiting for: reboot. 

# exit
cdimage ~# cd
cdimage ~# umount /mnt/gentoo/boot /mnt/gentoo/sys /mnt/gentoo/dev /mnt/gentoo/proc /mnt/gentoo
cdimage ~# reboot

# exit
cdimage ~# cd
cdimage ~# umount /mnt/gentoo/boot /mnt/gentoo/dev /mnt/gentoo/proc /mnt/gentoo
cdimage ~# reboot

Of course, don't forget to remove the bootable CD, otherwise the CD will be booted again instead of your new Gentoo system.

When you reboot you should see a new Gentoo Linux menu option in the EFI Boot Manager which will boot Gentoo.

Once rebooted in your Gentoo installation, finish up with Finalizing your Gentoo Installation.