atom feed14 messages in com.redhat.dm-develRe: [dm-devel] What is the deal with ...
FromSent OnAttachments
Phillip SusiFeb 15, 2011 7:21 pm 
Hannes ReineckeFeb 15, 2011 11:29 pm 
Curtis GedakFeb 16, 2011 9:19 am 
Phillip SusiFeb 16, 2011 11:33 am 
Phillip SusiFeb 16, 2011 11:37 am 
Curtis GedakFeb 16, 2011 12:18 pm 
Hannes ReineckeFeb 16, 2011 11:21 pm 
Phillip SusiFeb 17, 2011 6:57 am 
Hannes ReineckeFeb 17, 2011 7:04 am 
Phillip SusiFeb 17, 2011 7:13 am 
Alasdair G KergonFeb 17, 2011 8:53 am 
Curtis GedakFeb 17, 2011 8:54 am 
Alasdair G KergonFeb 17, 2011 8:58 am 
Phillip SusiFeb 19, 2011 9:04 pm 
Subject:Re: [dm-devel] What is the deal with the partition separator?
From:Hannes Reinecke (ha@suse.de)
Date:Feb 15, 2011 11:29:20 pm
List:com.redhat.dm-devel

On 02/16/2011 04:21 AM, Phillip Susi wrote:

It used to be that partitions device names just had a digit added on to the base disk device name. It seems that this became problematic at some point with device mapper and oddly named disks, and there have been several responses to it:

1) dmraid and (lib)parted now always add a 'p' between the base name and the partition number

2) kpartx from multipath-tools adds the 'p' only if the base name ends in a digit

3) Debian and Ubuntu's udev and init scripts tell kpartx to use 'part' instead of just 'p'.

4) gparted now explicitly tells dmraid to not use any character so that it behaves like older versions and is therefore compatible with the kpartx method that gparted has adopted, at least when the base name does not end with a digit.

Each of these components needs to agree on what the correct name is or chaos ensues. I would like to discuss the merits of each and try to decide on a standard.

Having thought about it for a moment, it seems to me that deciding on always adding the 'p' is the way to go, since the 'art' just makes things longer for no good reason, and if you only sometimes add the 'p' then you can't tell if a device name that ends in a digit that does not follow a 'p' is a whole disk, or a partition.

No.

The linux scheme since the dawn of time is to a) Add the partition number to the device node name b) If last letter of the device node name is a number, insert a 'p' between device node name and partition number

with the advent of persistent device names (via udev) the partition separator (for persistent links only!) is '-part'.

So you have

/dev/sda /dev/sda1 /dev/disk/by-id/scsi-0WhatAStupidName /dev/disk/by-id/scsi-0WhatAStupidName-part1

persistent device names are longish anyway, so we can as well use something readable for partitions.

Cheers,

Hannes