Disk mounting in recent Linuxes

[Gordon Tetlow]

On Oct 13, 2007, at 6:31 PM, Eric Anderson wrote:

> Ivan Voras wrote:
>> Hi,
>> I've installed a Linux (openSUSE) on a laptop and this is what I  
>> got by
>> default in fstab:
>> /dev/disk/by-id/scsi-SATA_Hitachi_HTS5412_HP0400BEG1922A-part2 /
>>            ext3       acl,user_xattr        1 1
>> /dev/disk/by-id/scsi-SATA_Hitachi_HTS5412_HP0400BEG1922A-part4 /data
>>            ext3       acl,user_xattr        1 2
>> /dev/disk/by-id/scsi-SATA_Hitachi_HTS5412_HP0400BEG1922A-part3 swap
>>            swap       defaults              0 0
>> A similar option (to use a device by id instead of location) also  
>> exists
>> for network cards.
>> (This is just a "FYI" post, I'm not complaining :) ).
>
>
> I was actually wondering if we should start labeling our filesystems  
> at newfs time in the installer for this type of setup.  There are a  
> handful of potential 'gotchas' though.

The big gotcha with GEOM_VOL_FFS (I don't know if pjd@ ever addressed  
this when he took it over) was that GEOM was undetermined in how it  
handled labels that overlapped. My original thought was to use the  
uuid field that I allocated in the FFS superblock (AFAIK, that's still  
unused). Whatever the uuid of the root device is would dictate the  
uuid for the system. Any volumes that didn't have the root uuid would  
be separated by namespace. ie /dev/vol/<uuid>/root if you took the  
root disk from another system and mounted on your system.

Of course, with the uuid moved to the filesystem, it actually gets  
easier in some sense (how do you figure out which labeled filesystem  
is your root filesystem if you have 2 labelled filesystems with the  
same uuid), although the loader will probably have to send it as hint  
to the kernel.

-gordon
-------------- next part --------------
A non-text attachment was scrubbed...
Name: PGP.sig
Type: application/pgp-signature
Size: 186 bytes
Desc: This is a digitally signed message part
Url : http://lists.freebsd.org/pipermail/freebsd-geom/attachments/20071115/8fec9c92/PGP.pgp