tips

tips

1. Windows Host file

Be logged in as a privileged user.

Open a DOS command window, type:

notepad C:\WINDOWS\system32\drivers\etc\hosts

Put the following line in hosts:

127.0.0.1 www.google.com

File > Save.

Now try to open http://www.google.com with any web browser on the PC.

Remove the line you added from hosts to restore access to the Googl;e

web site

2. Installing GRUB natively

Caution: Installing GRUB's stage1 in this manner will erase the normal boot-sector used by an OS.

GRUB can currently boot GNU Mach, Linux, FreeBSD, NetBSD, and OpenBSD directly, so using it on a boot sector (the first sector of a partition) should be okay. But generally, it would be a good idea to back up the first sector of the partition on which you are installing GRUB's stage1. This isn't as important if you are installing GRUB on the first sector of a hard disk, since it's easy to reinitialize it (e.g. by running `FDISK /MBR' from DOS).

If you decide to install GRUB in the native environment, which is definitely desirable, you'll need to create a GRUB boot disk, and reboot your computer with it.

Once started, GRUB will show the command-line interface. First, set the GRUB's root device to the partition containing the boot directory, like this:

grub> root (hd0,0)

If you are not sure which partition actually holds this directory, use the command find, like this:

grub> find /boot/grub/stage1

This will search for the file name /boot/grub/stage1 and show the devices which contain the file.

Once you've set the root device correctly, run the command setup :

grub> setup (hd0)

This command will install the GRUB boot loader on the Master Boot Record (MBR) of the first drive. If you want to put GRUB into the boot sector of a partition instead of putting it in the MBR, specify the partition into which you want to install GRUB:

grub> setup (hd0,0)

3. Installing GRUB using grub-install

Caution: This procedure is definitely less safe, because there are several ways in which your computer can become unbootable. For example, most operating systems don't tell GRUB how to map BIOS drives to OS devices correctly—GRUB merely guesses the mapping. This will succeed in most cases, but not always. Therefore, GRUB provides you with a map file called the device map, which you must fix if it is wrong.

If you still do want to install GRUB under a UNIX-like OS (such as gnu), invoke the program grub-install as the superuser (root).

The usage is basically very simple. You only need to specify one argument to the program, namely, where to install the boot loader. The argument can be either a device file (like `/dev/hda') or a partition specified in GRUB's notation. For example, under Linux the following will install GRUB into the MBR of the first IDE disk:

# grub-install /dev/hda

Likewise, under GNU/Hurd, this has the same effect:

# grub-install /dev/hd0

If it is the first BIOS drive, this is the same as well:

# grub-install '(hd0)'

Or you can omit the parentheses:

# grub-install hd0

But all the above examples assume that GRUB should use images under the root directory. If you want GRUB to use images under a directory other than the root directory, you need to specify the option --root-directory. The typical usage is that you create a GRUB boot floppy with a filesystem. Here is an example:

# mke2fs /dev/fd0 # mount -t ext2 /dev/fd0 /mnt # grub-install --root-directory=/mnt fd0 # umount /mnt

Another example is when you have a separate boot partition which is mounted at /boot. Since GRUB is a boot loader, it doesn't know anything about mountpoints at all. Thus, you need to run grub-install like this:

# grub-install --root-directory=/boot /dev/hda

By the way, as noted above, it is quite difficult to guess BIOS drives correctly under a UNIX-like OS. Thus, grub-install will prompt you to check if it could really guess the correct mappings, after the installation. The format is defined in Device map. Please be quite careful. If the output is wrong, it is unlikely that your computer will be able to boot with no problem.

Note that grub-install is actually just a shell script and the real task is done by the grub shell grub. Therefore, you may run grub directly to install GRUB, without using grub-install. Don't do that, however, unless you are very familiar with the internals of GRUB. Installing a boot loader on a running OS may be extremely dangerous.