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DEVLABEL(8)									      DEVLABEL(8)

       devlabel - Consistent/persistent storage device access through symlinking

       devlabel [action] [options]

       devlabel  is  a	script which manages symlinks to storage devices on your system.  This is
       accomplished by utilizing the inherent unique identifiers (UUID) that each device *should*
       have  in  order to maintain a correctly pointing symlink in the event that the device name
       changes (eg. /dev/sdc1 becomes /dev/sdd1).  By adding entries using devlabel its users can
       instead	reference  all	devices by their symlink and no longer care what the true name of
       their device is.  Similary, consistent raw device access can also  be  guaranteed  through
       use  of	devlabel as it treats entries in the format of /dev/raw/raw# as a special form of
       symlink so that each raw device can consistently be bound to the correct storage device.

       devlabel works with both IDE and SCSI storage and has been  integrated  into  the  hotplug
       system to allow USB, IEEE1394 (firewire) and PCI detection and consistency.

       reload Affirms  the  mappings of symlinks to storage devices.  If a device cannot be found
	      by its UUID, the existing symlink will be deleted.  If the device name has changed,
	      it will update the symlink. Both start and restart are synonyms for this command.

       add [-d device] [-s symlink]
	      Adds  the  entry symlink -> device and determines the UUID.  Alternatively, you can
	      add by UUID if the correct UUID of the device is known.  For this type of  add  you
	      specify  the  [-s  symlink]  and	the  [-u  UUID] Note that you must use the option
	      [--partnum partition#] to specify which partition of  the  device  with  that  UUID
	      should  have  a  symlink pointed to it.  If no partnum is specified, the symlink is
	      pointed just to the name of the disk itself.

       remove [-s symlink]
	      Removes the entry symlink

       status Returns the current status of all symlinks that are set to be configured.   If  the
	      symlink  is  a  raw device, it will return what major/minor combination it is bound

       printid [-d device]
	      Returns the identifier that devlabel finds for the device in question.

       -d <device>
	      The name of the device to be used for the specified action.

       -s <symlink>
	      The name of the symlink to be used.

       -u <uuid>
	      The UUID of the device to be used.  The -u option is currently only recognized dur-
	      ing an add command.

       --partnum <partition#>
	      The  partition number parameter is only supported in conjunction with the -u <uuid>
	      option while doing an add command.  Since UUIDs are currently disk specific and not
	      partition specific, devlabel must be told through this parameter which partition of
	      the disk to have the symlink pointed at.	If no value is given, the symlink will be
	      pointed at just the disk (e.g.  /dev/sdc instead of /dev/sdc5).

	      This  option  is	only  available  during an add.  If specified, it will cause this
	      device to be automatically mounted every time  devlabel  is  restarted  if,  within
	      /etc/fstab  ,  a	corresponding  entry  is  found for that symlink.  If no entry is
	      found, nothing will happen.  Automount is stored as an option in the 4th	field  of
	      the /etc/sysconfig/devlabel configuration file.

       -q     Quiet.

	      The  file containing all symlinks/rawdevices bindings to be made.  This file should
	      not be edited by hand.  Instead, the devlabel program should be used to  manipulate

       To  determine  the unique identifier associated with a SCSI device, devlabel uses the pro-
       gram /usr/bin/scsi_unique_id.  If this program cannot determine a  unique  identifier  for
       your block device then the device cannot be used with devlabel.

       Unique  identifiers  for  SCSI  devices are read from Page83 and Page80 of your SCSI block
       device as based on the SCSI standard.  This program will look for identifiers in the order
       of:  page 83 type 3, page 83 type 2, page 83 type 1, page 80, and then lastly page 83 type

       Unique identifiers for IDE devices are taken from /proc/ide/hd#/identify.

       Both IDE and SCSI identifiers will be prefaced with their identifier  type  and	concluded
       with  the  model  name of the storage device.  This entire string constitutes the device's

       Note that all partitions from the same device will have the  same  unique  identifier  but
       will be distinguishable from each other by their partition number.

       If  two	or  more storage devices on your system return the same UUID, none of them may be
       used with devlabel

       Hotpluggable storage devices which show themselves as SCSI devices  internally  (eg.  USB,
       firewire,  but  not  PCMCIA)  should  have carefully chosen symlink names (eg. /dev/smart-
       cardreader) as the UUIDs pulled from these devices are most likely being supplied  by  the
       connection hardware and not by the actual storage media itself.

       If  symlinks  setup  by devlabel are to be used within /etc/fstab , these symlinks must be
       located on the root partition so that they are accessable by  /etc/rc.d/rc.sysinit  during
       the boot-up process.

       Devlabel does not currently handle interdisk renaming events.  These events occur when one
       partition within a disk gets deleted and all of the partitions after it shift down a  num-
       ber  (e.g.  when /dev/sda6 is deleted, /dev/sda7 becomes /dev/sda6).  Currently IA-64 sys-
       tems utilize the Intel Extensible Firmware Interface (EFI)  Spec  for  partition  specific
       identifiers  which would make this functionality possible, but until the spec becomes more
       widely used, its usage will not be adopted (or worthwhile) within devlabel.

       UUIDs are prefaced with a tag to alert devlabel as to  where  the  identifier  came  from.
       Currently, devlabel supports SCSI firware identifiers and IDE identifiers.

       S83.3  SCSI Page 83, Type 3 identifier

       S83.2  SCSI Page 83, Type 2 identifier

       S83.1  SCSI Page 83, Type 1 identifier

       S80    SCSI Page 80 identifier (Serial Number)

       S83.0  SCSI Page 83, Type 0 identifier

       I      IDE identifier as found in words 11-20 of /proc/ide/<device>/identify

       Gary Lerhaupt (gary_lerhaupt@dell.com)

Version 0.4				   January 2003 			      DEVLABEL(8)
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