concerning loader.conf(5)

[Warren Block]

On Sat, 14 Dec 2013, Eric Dynamic wrote:

>   There's the issue where you move disks from installed system A to a
>   different motherboard
>   and the system can't boot because it remembers the old system's device
>   names.
>   Where is the fix for this documented?

Labels are the easiest fix, a static name that sticks with a partition 
or filesystem regardless of changing device numbers.

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-glabel.html

GPT labels are the preferred method, although that section does not 
mention them yet.  UFS labels work well also.

>   I examined /boot/defaults/loader.conf and I believe the lines in
>   question - for a /boot/loader.conf
>   file I would create as the override for the problem are these:
>   #currdev="disk1s1a"     # Set the current device
>   #root_disk_unit="0"     # Force the root disk unit number
>   #rootdev="disk1s1a"     # Set the root filesystem
>   I'll guess that "rootdev" is all I need to specify, or possibly
>   "currdev" as well.
>   I have this nit to pick: the loader.conf man page does NOT describe
>   these labels at all,
>   and the Online Manual in describing the boot process makes no mention
>   of this mechanism,
>   either.

The only one likely to be needed is vfs.root.mountfrom, which may need 
to be set to the UFS filesystem that contains /etc/fstab.