Can't find kernel, finds slices but no files on them

Matthew Seaman matthew at
Thu Sep 20 06:36:28 UTC 2012

On 19/09/2012 23:59, Polytropon wrote:
> The terminology is simple and as follows:
> A disk is a disk, e. g. /dev/ad0.
> A slice is a "DOS primary partition" on the disk, e. g. /dev/ad0s1.
> A partition is a subdivision of a slice, e. g. /dev/ad0s1a.
> Partitions can be used without a slice that encloses them,
> e. g. /dev/ad0a; this is called "dedicated mode" (because
> some obscure operating systems may have problems accessing
> something they cannot even understand).
> Tools like dump and restore operate on partitions.
> Tools like dd operate on everything.

What Polytropon says is perfectly correct, and accurate for setups using
MBR, fdisk(8) and bsdlabel(8).  However nowadays, the move is towards
using gpart(8) and the terminology is different there.  It looks like this:

% gpart show -p da0
=>       34  134217661    da0  GPT  (64G)
         34        128  da0p1  freebsd-boot  (64k)
        162    4194304  da0p2  freebsd-swap  (2.0G)
    4194466  130023229  da0p3  freebsd-zfs  (62G)

'da0' is the disk -- this is from a VM emulating a SAS controller, hence
'da' as the disk device.  That's not gpart specific, and you'll also
commonly see 'ad' or 'ada' for disk devices, plus some others specific
to certain hardware RAID controllers.

The disk has three partitions: da0p1, p2 and p3 of the indicated types.
There's also a freebsd-ufs type for those that don't want ZFS.

That's really all there is to it for all practical purposes.  There's no
need for 'partitions inside slices' or 'logical partitions' or any of
that malarkey.  I believe you could create partitions inside partitions
recursively to your heart's content but never cared enough to try that
out -- I think the device names would come out like 'da0p3p1' but I
could be wrong.



Dr Matthew J Seaman MA, D.Phil.

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