Partitioning for multiple systems

[illoai at gmail.com]

2009/4/26 Michael David Crawford <mdc at prgmr.com>:
> I have a machine I plan to use solely for testing.  I have FreeBSD
> 8.0-CURRENT on it right now, and would like to add FreeBSD 7.2-RC2 as well
> as CentOS 5.3 Linux.
>
> Presently I have three Master Boot Record primary partitions - "slices" in
> the FreeBSD parlance, if I understand correctly:
>
> - A Linux slice to be used for CentOS' /boot
> - A BSD slice subdivided into partitions that hold 8.0-CURRENT
> - A big FAT slice (so to speak) meant to be split up for 7.2 and CentOS
>
> A PC-style Master Boot Record can hold a maximum of four primary partitions,
> or it can hold three primaries and a single extended partition that is
> subdivided into logical partitions.
>
> The geometries of the logical partitions aren't given in the MBR, but exist
> as a linked list.
>
> I *should* be able to split that FAT slice up into a primary for 7.2 and an
> extended partition that will hold CentOS' other partitions; however:
>
> In Googling about this, I have read some dire warnings about FreeBSD being
> unable to understand logical partitions; apparently installing FreeBSD
> *before* an extended partition will result in all your logicals getting
> trashed.  One is advised to put all the FreeBSD MBR partitions *after* the
> extended partition.
>
> Is that the case?  Have you any advice for me?

I haven't found that to be the case at all.  I don't have
as many variable as you, but on my dual boot I have
ad4s1[a-g] FreeBSD
ad4s2 Linux /boot
ad4s3 extended
ad4s5 Linux swap
ad4s6 Linux /

and I have tested using nothing but logical slices for
Linux (including /boot) and it works fine.

I would advise (roughly, you can do it as you please)
adNs1 FreeBSD 7.x / /var /usr /tmp*
adNs2 FreeBSD 8 / /var /usr /ports*
adNs3 Fat32 /home
adNs4 extended
adNs5 . . . Linux /boot / & swap

I would install Linux first and just use grub as the boot loader
for everyone.

(*whichever, but they can be mounted on both FreeBSDs,
don't forget to symlink /usr/ports)

>
> One more thing: if it's possible, I'd like for the /home directory to be
> shared between both of my FreeBSD installations.  In a normal installation,
> there is a real /usr/home directory, with /home being a symbolic link.

I would mount a Fat32 partition for /home and use it for all
3 OSes.  And symlink /usr/home to /home.

>
> If I'm running FreeBSD out of one MBR partition (or slice), can I mount a
> directory that's in a different one?

Yes.

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