Linux and FreeBSD label hard drives and partitions after two differents schemes. This section explains the main differences between the two schemes.
FreeBSD needs only one entry in the primary partition table on your hard
drive. This primary partition is called a ``slice'' in FreeBSD
terminology. It then uses the program disklabel
to make several logical
partitions in this primary partition. These logical partitions are called
``partitions'' in FreeBSD terminology. This concept is similar to the way
Linux (and DOS) handles logical partitions in an extended partition. Note that
the Linux fdisk
program doesn't display the partitions in a FreeBSD slice
from the main menu, but it can display BSD disklabel information if you give
the command `b'. The output is something like this (/dev/hda4
is the
FreeBSD slice):
# fdisk /dev/hda
Command (m for help): p
Disk /dev/hda: 64 heads, 63 sectors, 621 cylinders
Units = cylinders of 4032 * 512 bytes
Device Boot Begin Start End Blocks Id System
/dev/hda1 * 1 1 27 54400+ 83 Linux native
/dev/hda2 28 28 55 56448 83 Linux native
/dev/hda3 56 56 403 701568 83 Linux native
/dev/hda4 404 404 621 439488 a5 BSD/386
Command (m for help): b
Reading disklabel of /dev/hda4 at sector 1624897.
BSD disklabel command (m for help): p
8 partitions:
# size offset fstype [fsize bsize cpg]
a: 64512 1624896 4.2BSD 0 0 0 # (Cyl. 404 - 419)
b: 104832 1689408 swap # (Cyl. 420 - 445)
c: 878976 1624896 unused 0 0 # (Cyl. 404 - 621)
e: 64512 1794240 4.2BSD 0 0 0 # (Cyl. 446 - 461)
f: 645120 1858752 4.2BSD 0 0 0 # (Cyl. 462 - 621)
BSD disklabel command (m for help): q
#
The letters `a'...`f' in the first column are the same labels as shown below in the example for a FreeBSD slice. The letter `b' designates the swap partition while `c' designates the whole slice. See the FreeBSD documentation for more information on the ``standard'' way of assigning these letters to different partition types.
The hard drives are labelled in the following way in Linux and FreeBSD:
Linux FreeBSD
First IDE drive /dev/hda /dev/wd0
Second IDE drive /dev/hdb /dev/wd1
First SCSI drive /dev/sda /dev/sd0
Second SCSI drive /dev/sdb /dev/sd1
The partitions (FreeBSD slices) on a drive are labelled in the following way
(/dev/hda
is used as an example):
Linux FreeBSD
First primary partition /dev/hda1 /dev/wd0s1
Second primary partition /dev/hda2 /dev/wd0s2
Third primary partition /dev/hda3 /dev/wd0s3
Fourth primary partition /dev/hda4 /dev/wd0s4
The partitions in a FreeBSD slice is labelled in the following way
(/dev/hda4
is the FreeBSD slice in the example):
Linux label FreeBSD label Default FreeBSD mount point
/dev/hda5 /dev/wd0s4a /
/dev/hda6 /dev/wd0s4b swap
/dev/hda7 /dev/wd0s4e /var
/dev/hda8 /dev/wd0s4f /usr
If you run dmesg
in Linux you will see this as (The linux kernel must be
build with UFS support for this to work. See section
Installing and preparing Linux):
Partition check:
hda: hda1 hda2 hda3 hda4 < hda5 hda6 hda7 hda8 >
If you have installed FreeBSD in the /dev/sdb3
slice, and
/dev/sdb2
is a Linux extended partition containing two logical
partitions (/dev/sdb5
and /dev/sdb6
), the previous example
would look like this:
Linux label FreeBSD label Default FreeBSD mount point
/dev/sdb7 /dev/sd1s3a /
/dev/sdb8 /dev/sd1s3b swap
/dev/sdb9 /dev/sd1s3e /var
/dev/sdb10 /dev/sd1s3f /usr
This will be shown as
Partition check:
sdb: sdb1 sdb2 < sdb5 sdb6 > sdb3 < sdb7 sdb8 sdb9 sdb10 >
in the output from dmesg
.
If you have a Linux extended partition after your FreeBSD slice your in
for trouble. Since most Linux kernels installation floppies are build without
UFS support, they will not recognise the FreeBSD partitions inside the
slice. What should have have been seen as (/dev/hda3
is the FreeBSD
slice and /dev/hda4
is the Linux extended partition)
Partition check:
hda: hda1 hda2 hda3 < hda5 hda6 hda7 hda8 > hda4 < hda9 hda10 >
is seen as:
Partition check:
hda: hda1 hda2 hda3 hda4 < hda5 hda6 >
This can give you the wrong device assignment and cause the loss of data. My advice is to always put your FreeBSD slice after any Linux extended partitions, and do not change any logical partitions in your Linux extended partitions after installing FreeBSD!