FreeBSD slices and the Boot Manager

Conny Andersson ataraxi at
Sun Jul 28 20:06:13 UTC 2013

Hi Warren and Polytropon,

A few minutes ago I booted up from a FreeBSD-8.4-RELEASE-amd64-memstick.img 
to experience that it is sysinstall that is used in that release.

Next, I did a 'dummy' custom installation. And, as I supposed sysinstall 
recognized disk ada0 as ad4 and disk ada1 as ad6. Then I aborted sysinstall 
and rebooted in to my FreeBSD 8.3-Release.

Well, AHCI (Serial ATA Advanced Host Controller Interface driver) seems 
involved when identifying disks and slices. But, only on newer computers 
who has this option set to on in the BIOS. Maybe, bsdinstall in FreeBSD 9.0 
and onwards can make use of AHCI directly.

When I bought this workstation and installed FreeBSD I thought something 
was very much wrong with the wiring of the hardware/disks and I phoned 
Dell's support ... without being much wiser.

My old Dell workstation on which I have used all the FreeBSD's from release 
4.8 up to 8.0 I always got ad0 and ad1 as the disks in use. So, I had to 
search the Internet for an answer why my new computer numbered disks oddly. 
And I found your web page Warren 
( and I also read the 
ahci man page. I also had to edit my /etc/fstab accordingly.

My FreeBSD 8.3 /etc/fstab:

# Device		Mountpoint      FStype  Options      Dump   Pass#
/dev/ada1s3b            none            swap    sw           0      0
/dev/ada1s3a            /               ufs     rw           1      1
/dev/ada1s3d            /home           ufs     rw           2      2
/dev/acd0               /cdrom          cd9660  ro,noauto    0      0
proc                    /proc           procfs  rw           0      0
linproc      /compat/linux/proc       linprocfs rw           0      0

Apropos labels, I only have two filesystems (+swap) on each slice, as I 
only run a desktop workstation. I do that following Greg Lehey's advise in 
his book "The Complete FreeBSD" 4th Edition.

More apropos labels: The latest BIOS version 2.4.0 for Dell T1500 does not 
support UEFI/GPT/GUID. As far as I know, Dell only have the Unified 
Extensible Firmware Interface on its PowerEdge servers.

(The reason why I want to merge two slices into one big ada1s1 is the need 
for more disk space for FreeBSD 8.4 and keep 8.3 as it is, but then as 
slice 2).

Thank you,


> On Sun, 28 Jul 2013, Warren Block wrote:

> On Sun, 28 Jul 2013, Polytropon wrote:
>> On Sat, 27 Jul 2013 19:39:30 +0200 (CEST), Conny Andersson wrote:
>>> A very important question is if sysinstall's option "Install the FreeBSD
>>> Boot Manager" detects that I have a FreeBSD 8.3 and detect it as slice 2 
>>> on
>>> disk 1?
>> I'm not sure I'm following you correctly. The sysinstall program
>> is considered obsolete, the new system installer is bsdinstall.
> AFAIK, sysinstall is still used in FreeBSD 8.X, and bsdinstall does not have 
> a boot manager option anyway.
>>> So it becomes a boot option when I am rebooting? (Maybe the slice
>>> may come up as ad6s2, because AHCI in FreeBSD 8.4 isn't enabled at the 
>>> time
>>> of the install.)
> Sorry, I don't understand this at all.  AHCI should not be involved with 
> identifying slices.
>> That is a _good_ consideration! To make sure things work independently
>> from "boot-time recognition", use labels for the file system and then
>> mount them by using the labels. Encode the OS version number in the
>> labels, so it's even easier to deal with them. Use "newfs -L" on
>> un-mounted partitions (you can do that from the install media).
> For existing filesystems, that would be tunefs -L.  And agreed, filesystem 
> labels make relocation much easier.

More information about the freebsd-questions mailing list