Configuring LILO

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Configuring LILO

LILO is easily configurable by editing the lilo.conf file then running LILO to use the new configuration options. The configuration for LILO created by EMAC and shipped with a system will usually suffice, although customization may be required. The information provided here provides a description for the important lilo configuration options.

Typical lilo.conf

boot=/dev/sda
map=/boot/map

lba32
#linear
disk=/dev/sda
bios=0x80
read-only
prompt
timeout=5
vga=normal
install=text
compact
#This is for bootloader input from the serial console (ttyS0,9600,8,n,1):
#serial=0,9600n8

image=/boot/bzImage
        root=/dev/sda1
        label=emac-oe
        #This is for boot messages redirected to the serial console (ttyS0):
        append="console=ttyS0,115200"

Sections of the LILO Configuration File

The LILO configuration file is split into two sections: global and per-image. The global section specifies options that pertain to LILO itself and to all images specified in the file. The per-image section specifies options that apply to a specific image, some of which may override the global options.

Global Options

The LILO configuration file needs the following options, at a minimum, configured for the global settings:

• disk This option specifies the disk to which the LILO bootloader needs to be written. This should always point to the device node currently associated with the disk. For example, when mounted on a desktop, this may be /dev/sdc, which is (usually) the third "SCSI" device connected to the system. If it were mounted through the IDE subsystem instead, its device node would appear like /dev/hdc instead.
• map This option specifies the location of the map file to use. Usually, this will be /boot/map.
• lba32 This option tells LILO to use 32-bit Logical Block Addresses instead of cylinder/head/sector addresses. This is needed for any disk with more than 1024 cylinders. Since the vast majority of modern drives have more than 1024 cylinders, this option should always be specified.
• boot This option specifies the device which contains the boot sector. As with the disk option, this should always be the device node associated with the disk on the current system. For example, boot=/dev/sdc

Additional useful options:

• vga For systems which have video, this option specifies the video mode the device should use while booting.
• serial This option allows the bootloader to accept input from a serial line and specifies a serial device and configuration to which a console should be attached. For example, to use the /dev/ttyS0 serial device (the default console port on many boards) as a serial console which communicates as 115,200 baud, 8 bits, with no stop bits: serial=0,115200n8
• timeout This specifies the amount of time to wait before timing out and continuing on with the boot process using the configured defaults. This allows some time for the user to hit TAB to specify additional options to the kernel. This value is specified in deciseconds and must be greater than 0. For example, to set this value to 4.3 seconds: timeout=43
• read-only This option tells LILO to mount the root filesystem as read-only. This is usually desired, since the Linux kernel will remount the device as writeable (if it needs to) once the boot process has been handed over to it.
• install This option specifies the type of screen which will be seen when the bootloader starts. Normally, this will be set to text, which presents the simple interface shown in the examples on this page. The menu option provides a nicer way to select an image to boot, but is usually not desirable to have on an embedded machine. The bitmap option provides a graphical boot screen which looks very nice on a desktop installation, but is usually only used on an embedded machine when the product calls for showing graphics as early in the boot process as possible; a logo is typically placed here in such a case.
• compact Speeds up booting by merging read requests.

Per-Image Options

The following options are needed to configure images to be available to boot with LILO:

• image This option specifies the location of the kernel to boot. Commonly, this will be /boot/bzImage or /boot/bzImage-custom-3.10.2. bzImage is commonly a symbolic link to the actual kernel filename. This is done so that lilo.conf does not have to be changed when a new kernel is installed.
• root This option specifies the root partition of the device to mount for the image. This is typically /dev/hda1 or /dev/sda1
• label This option tells LILO by what name to call the image. For instance, this is usually label=emac-oe for a standard EMAC image, but for a custom product under development, it might be label=custom-image-test-v3

Working with LILO Configurations

The above information describes the common options and how to set them. Additional information can be found by reading through the manual page for lilo.conf. This manpage is available on many sites online.

Using these options to create a configuration file is done most easily by copying the EMAC provided LILO configuration file, then modifying the copy. It is a good practice to make sure a bootable flash card is set aside in case of difficulties with getting the modified flash card back into a bootable state. Also, keep a separate copy of lilo.conf e.g. lilo.conf.boot to use when installing lilo from a Linux PC so that the boot and disk options can be set up.