The Linux+FreeBSD mini-HOWTO: The FreeBSD way of labelling hard drives

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Linux and FreeBSD label hard drives and partitions after two differents schemes. This section explains the main differences between the two schemes.

2.1 FreeBSD « slices » and « partitions »

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 can’t display the partitions in a FreeBSD slice, the output is something like this (/dev/hda4 is the FreeBSD slice):


hafnium:~# 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      375   701568   83  Linux native
/dev/hda3          376      376      403    56448   83  Linux native
/dev/hda4          404      404      621   439488   a5  BSD/386

Command (m for help): q
hafnium:~#

2.2 Drive and partition labelling in Linux and FreeBSD

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 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

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