How does FreeBSD access NetBSD, OpenBSD?

Scott Bennett bennett at
Fri Jan 28 09:08:51 PST 2005

     On Fri, 28 Jan 2005 11:18:55 -0500 (EST) Jerry McAllister
<jerrymc at> wrote:
>> I have FreeBSD, OpenBSD, and NetBSD on the same hard drive of my system.
>> How can I mount the NetBSD or OpenBSD partitions from FreeBSD?
>> Slice 1 - Ext3fs for data between linux/bsd
>> Slice 2 - OpenBSD slice with 4 ufs partitions and swap (a,b,e,f,g)
>> Slice 3 - FreeBSD slice with 4 ufs partitions and swap (a,b,d,e,f)
>> Slice 4 - Extended slice composed of:
>>    Slice 5 - NetBSD slice with 4 ufs partitions and swap (a,b,e,f,g)
>>    Slice 6 - Unformatted as of yet.
>Hmmm,  First thing I see is that only 4 slices are allowed on a drive.

     Not true.  In fact, I have 8 slices on one of my drives.  The slice
entries in the Master Boot Record, wherein they are known as "primary
partition" entries, are four in number, but one of those four can point,
instead of to a "partition" (i.e., "slice" in UNIX terms), to a chain of
"logical partition" table entries, known collectively as the "extended
partition".  The FreeBSD kernel appears to have no trouble with this at
     The main limitation w.r.t. FreeBSD is that the slice containing the
bootable root file system must be a "primary" rather than a "logical".
This limitation probably means that FreeBSD's boot loader isn't smart
enough to understand and follow the logical partition/slice chain to
locate the file system containing the kernel to be loaded.  From what
I've read, LINUX's LILO boot loader *can* do this.  Perhaps the FreeBSD
loader will be made smarter someday, but I'd guess that would be a low-
priority item on the developer team's to-do list.

                                  Scott Bennett, Comm. ASMELG, CFIAG
* Internet:       bennett at                              *
* "A well regulated and disciplined militia, is at all times a good  *
* objection to the introduction of that bane of all free governments *
* -- a standing army."                                               *
*    -- Gov. John Hancock, New York Journal, 28 January 1790         *

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