bootable freebsd slice's limit

Brandon J. Wandersee brandon.wandersee at
Sun Mar 27 15:18:53 UTC 2016

Teng Zhang writes:

> In man fdisk(8), it refers to
> "Note that bootable FreeBSD slices (the ``*/*'' file system) must lie
> completely within the first 1024 cylinders; if this is not true, booting
> may fail."
>        my confusion is whether this limit is aimed at  just i386 platform
> or all platforms that freebsd supports. Could you please tell me the actual
> condition ?

Hopefully someone will correct me if I'm wrong, but I don't believe the
limitation is related to machine architecture. Rather, it has to do with
how the legacy bootloader handles older disks with a 512k sector size
and an MBR partition table.

I would guess that you are asking out of concern for on-disk filesystem
alignment? Is there any particular reason you cannot use GPT via
gpart(8), rather than MBR via fdisk(8)?


::  Brandon J. Wandersee
::  brandon.wandersee at
::  --------------------------------------------------
::  'The best design is as little design as possible.'
::  --- Dieter Rams ----------------------------------

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