Shared OS installation

In many cases, you won't want to install FreeBSD on the system by itself: you may need to use other operating systems as well. In this chapter, we’ll look at what you need to do to prepare for such an installation. If you're only running FreeBSD on the machine, you don't need to read this chapter, and you can move onto Chapter 5, Installing FreeBSD.

Before you start the installation, read this chapter carefully. It's easy to make a mistake, and one of the most frequent results of mistakes is the total loss of all data on the hard disk.

Currently, only the ia32 (Intel) port of FreeBSD is capable of sharing with other operating systems. We'll concentrate on how to share your system with Microsoft, because that's both the most difficult and the most common, but most of this chapter applies to other operating systems as well. You may want to refer to the discussion of Microsoft and FreeBSD disk layouts on page 34.

Separate disks

The first question is: do you need to share a disk between FreeBSD and the other operating system? It's much easier if you don't have to. In this section, we'll look at what you need to do.

Many operating systems will only boot from the first disk identified by the BIOS, usually called the C: disk in deference to Microsoft. FreeBSD doesn't have this problem, so the easiest thing is to install FreeBSD on the entire second disk. BIOS restrictions usually make it difficult to boot from any but the first two disks.

In this case, you don't really need to do anything special, although it's always a good idea to back up your data first. Install FreeBSD on the second disk, and choose the Boot Manager option in the partition editor (page 64). This will then give you the choice of booting from the first or second disk. Note that you should not change the order of disks after such an installation; if you do, the system will not be able to find its file systems after boot.

Sharing a disk

If you intend to share a disk between FreeBSD and another operating system, the first question is: is there enough space on the disk for FreeBSD? How much you need depends on what you want to do with FreeBSD, of course, but for the sake of example we'll take 120 MB as an absolute minimum. In the following section, we'll consider what to do if you need to change your partitions. If you already have enough space for a FreeBSD partition (for example, if you have just installed Microsoft specifically for sharing with FreeBSD, and thus have not filled up the disk), continue reading on page 66.

Sharing with Linux or another BSD

Sharing with other free operating systems is relatively simple. You still need to have space for FreeBSD, of course, and unlike Microsoft, there are no tools for shrinking Linux or BSD file systems: you'll have to remove them or recreate them. You can find some information about sharing with Linux in the mini-Howto at http://www linux.org/docs/ldp/howto/mini/Linux+FreeBSD.html.

NetBSD and Open BSD file systems and slices are very similar to their FreeBSD counterparts. They're not identical, however, and you may find that one of the systems recognizes the partition of another system and complains about it because it's not quite right. For example, NetBSD has a d partition that can go outside the boundary of the slice. FreeBSD does not allow this, so you get a harmless error message.

Repartitioning with FIPS

Typically, if you've been running Microsoft on your machine, it will occupy the entire disk. If you need all this space, of course, there's no way to install another operating system as well. Frequently, though, you'll find that you have enough free space in the partition. Unfortunately, that’s not where you want it: you want the space in a new partition. There are a number of ways to do so:

In the rest of the section, we'll look at how to shrink a partition with FIPS. If you do it with PartitionMagic, the details are different, but the principles are the same. In particular:

Before repartitioning your disk, make a backup. You can shoot yourself in the foot with this method, and the result will almost invariably be loss of data.

If you've been running Microsoft on your system for any length of time, the data in the partition will be spread all around the partition. If you just truncate the partition, you'll lose a lot of data, so you first need to move all the data to the beginning of the partition. Do this with the Microsoft defragmentation utility. Before proceeding, consider a few gotchas:

For further information, read the FIPS documentation in /cdrom/tools/fips.doc. In particular, note these limitations:

Repartitioning—an example

In this section, we'll go through the mechanics of repartitioning a disk. We'll start with a disk containing a single, complete Microsoft system.

First, run the Microsoft error check utility on the partition you want to split. Make sure no "dead" clusters remain on the disk.

Next, prepare a bootable floppy. When you start FIPS, you will be given the opportunity to write backup copies of your root and boot sector to a file on drive A:. These will be called ROOTBOOT.00x, where x represents a digit from 0 to 9. If anything goes wrong while using FIPS, you can restore the original configuration by booting from the floppy and running RESTORRB.

Before starting FIPS you must defragment your disk to ensure that the space to be used for the new partition is free. If you're using programs like IMAGE or MIRROR, note that they store a hidden system file with a pointer to your mirror files in the last sector of the hard disk. You must delete this file before using FIPS. It will be recreated the next time you run MIRROR. To delete it, in the root directory enter:

C\:gt; attrib -r -s -h image.idx  for IMAGE
C\:gt; attrib -r -s -h mirorsav.fil  for MIRROR

Then delete the file.

If FIPS does not offer as much disk space for creation of the new partition as you expect, this may mean that:

If you are running early versions of MS-DOS (before 5.0), or another operating system, such as OS/2, or you are using programs like Stacker, SuperStor, or Doublespace, read the FIPS documentation for other possible problems.

Running FIPS

After defragmenting your Microsoft partition, you can run FIPS:

C:\gt; D:             changetoCD-ROM
D:\gt; cd \tools      Make sure you're in the tools directory
D:\tools\gt; fips     and start the FIPS program
... a lot of copyright information omitted 
Press any key              do what the computer says
Which Drive (1=0x80/2=0x81)?

The message Which Drive may seem confusing. It refers to BIOS internal numbering. Don't worry about it: if you want to partition the first physical drive inthe system, (C:), enter 1, otherwise enter 2. Like the BIOS, FIPS handles only two hard disks.

If you start FIPS under Windows, it will complain and tell you to boot from a floppy disk. It won't stop you from continuing, but it is a Bad Idea to do so.

Next, FIPS reads the root sector of the hard disk and displays the partition table:

This shows that only the first partition is occupied, that it is bootable, and that it occupies the whole disk (19571 MB, from Cylinder 0, Head 1, Sector 1 to Cylinder 2047, Head 238, Sector 63). It also claims that this makes 40083057 sectors. It doesn't: the cylinder number has been truncated, and FIPS complains about a partition table inconsistency, which it fixes. After this, we have:

Don't worry about the "bootable" flag here—we'll deal with that in the FreeBSD installation. First, FIPS does some error checking and then reads and displays the boot sector of the partition:

Checking boot sector ... OK
Press any Key                  do what it says
Bytes per sector: 512
Sectors per cluster: 32
Reserved sectors: 32
Number of FATs: 2
Number of rootdirectory entries: 0
Number of sectors (short): 0
Media descriptor byte: f8h
Sectors per FAT: 9784
Sectors per track: 63
Drive heads: 240
Hidden sectors: 63
Number of sectors (long): 40083057
Physical drive number: 80h
Signature: 29h

After further checking, FIPS asks you if you want to make a backup floppy. Enter your formatted floppy in drive A: and makethe backup. Next, you see:

Enter start cylinder for new partition (35 - 2650):
Use the cursor keys to choose the cylinder, <enter> to continue
Old partition  Cylinder  New Partition
  258.4 MB        35       19313.4 MB

Use the Cursor Left and Cursor Right keys to adjust the cylinder number at which the new partition starts. You can also use the keys Cursor Up and Cursor Down to change in steps of ten cylinders. FIPS updates the bottom line of the display to show the new values selected. Initially, FIPS chooses the smallest possible Microsoft partition, so initially you can only increase the size of the old partition (with the Cursor Right key). When you're happy with the sizes, press Enter to move on to the next step.

In this example, we choose equal-sized partitions:

To ensure that the partition is recognized, reboot immediately. Make sure to disable all programs that write to your disk in CONFIG.SYS and AUTOEXEC.BAT before rebooting. It might be easier to to rename the files or to boot from floppy. Be particularly careful to disable programs like MIRROR and IMAGE, which might get confused if the partitioning is not to their liking. After rebooting, use CHKDSK or Norton Disk Doctor to make sure the first partition is OK. If you don't find any errors, you may now reboot with your normal CONFIG.SYS and AUTOEXEC.BAT. Start some programs and make sure you can still read your data.

After that, you have two valid Microsoft partitions on your disk. We'll look at what to do with them in the next chapter. The specific differences from a dedicated install are on page 66, but you'll need to start from the beginning of the chapter to do the install.