Dual Booting/9.2

From PC-BSD Wiki
Revision as of 13:31, 24 July 2013 by FuzzyBot (Talk | contribs)

Jump to: navigation, search

(Sorry for the inconvenience)


A PC-BSD® installation assumes that you have an existing primary partition to install into. If your computer has only one disk and PC-BSD® will be the only operating system, it is fine to accept the default partitioning scheme. However, if you will be sharing PC-BSD® with other operating systems, care has to be taken that PC-BSD® is installed into the correct partition; otherwise, you may inadvertently overwrite an existing operating system.

If you wish to install multiple operating systems on your computer, you will need the following:

  • a partition for each operating system. Many operating systems, including PC-BSD®, can only be installed into a primary partition. This means that you will need to use partitioning software as described in Partitioning the Hard Drive.
  • a boot loader that allows you to select which operating system you wish to boot into. Depending upon the choice of boot loader and the operating systems that you install, you may or may not have to configure the boot loader to list all of the installed operating systems. Also, depending upon the order that you install the operating systems, the existing MBR data may be overwritten. This section will describe the configuration of several different boot loaders and how to restore an overwritten MBR.
  • a backup of any existing data. This backup should not be stored on your computer's hard drive but on another computer; on removable media, such as a USB drive; or burnt onto a DVD media. If you are careful in your installation, everything should go fine. However, you will be glad that you made a backup should something go wrong.

Choosing the Installation Partition

When installing PC-BSD® onto a computer that is to contain multiple operating systems, care must be taken to select the correct partition in the Disk Selection screen of the installation. On a system containing multiple partitions, each partition will be listed. Highlight the partition that you wish to install into and make sure that you do not select a partition that already contains an operating system or data that you wish to keep.

DANGER! make sure that you click the "Customize" button while in the "Disk Selection" screen. If you just click Next without customizing the disk layout, the installer will overwrite the contents of the primary disk.

If you install PC-BSD® on a computer that already contains an operating system, the first time you reboot, your computer will automatically boot into the previous operating system. You will need to configure a boot loader utility to recognize all of the operating systems that are installed and to provide you with a boot menu where you can select which operating system to boot into.

GRUB version 2 supports both the MBR and GPT formats.

In this example, PC-BSD® is installed on the third primary partition of the first hard drive using the MBR format:

menuentry "PCBSD 9.1" {

insmod ufs2 set root=(hd0,2,a) kfreebsd /boot/loader



  • menuentry: the text between the quotes will be displayed in the boot menu and can be anything that makes sense to you.
  • insmod: some distros require this instruction to load the UFS2 kernel module.
  • set root: the root of the partition containing PC-BSD®, as determined by the ls command described in the previous section. Always add the a at the end to refer to the BSD boot partition on the specified disk and partition.
  • kfreebsd: used to load the primary boot image. For FreeBSD and PC-BSD®, always use /boot/loader.

The entry for the same installation (third partition on first drive), but with the GPT box checked, will differ slightly in the set root line.

menuentry "PCBSD 9.1" {

insmod ufs2 set root=(hd0,msdos2,bsd1) kfreebsd /boot/loader


If you installed PC-BSD® onto the second hard drive, you need to invoke the map and chainloader commands in order to boot from the second disk. In this example, PC-BSD® is installed in the first partition of the second drive and the box to partition disk with GPT was not checked.

menuentry "PC-BSD 9.1" {

map (hd0) (hd1) map (hd1) (hd0) map --hook chainloader (hd0,0)/boot0 boot


The entry if the GPT box was checked looks like this:

menuentry "PC-BSD GPT" {

map (hd0) (hd1) map (hd1) (hd0) map --hook chainloader (hd0,0)/pmbr boot


If you installed ZFS, several modules need to be loaded. Here is a sample entry with the GPT box checked:

menuentry "PC-BSD 9.1" {

  insmod zfs   search -s -l tank0   kfreebsd /freebsd@/boot/kernel/kernel   kfreebsd_module_elf /freebsd@/boot/kernel/opensolaris.ko   kfreebsd_module_elf /freebsd@/boot/kernel/zfs.ko   kfreebsd_module /freebsd@/boot/zfs/zpool.cache type=/boot/zfs/zpool.cache   set kFreeBSD.vfs.root.mountfrom=zfs:tank0/freebsd


After a GRUB2 configuration change you need to run a command to update the configuration. This command varies by distro:

  • sudo update-grub on a Debian-based system
  • grub2-mkconfig -o /boot/grub2/grub.cfg as the superuser under Fedora 16 or Gentoo
  • grub-mkconfig -o /boot/grub/grub.cfg when using Sabayon

For more information please refer to the GNU GRUB Manual[1].


  1. http://www.gnu.org/software/grub/manual/grub.html
Other languages:German 100% • ‎English 100% • ‎French 36%
Personal tools