DEVLABEL(8)						      System Manager's Manual						       DEVLABEL(8)

NAME

       devlabel - Consistent/persistent storage device access through symlinking

SYNOPSIS

       devlabel [action] [options]

DESCRIPTION

       devlabel is a script which manages symlinks to storage devices on your system.  This is accomplished by utilizing the inherent unique iden-
       tifiers (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.

ACTIONS

       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  sym-
	      link 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 to.

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

OPTIONS

       -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 during 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).

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

       -q     Quiet.

FILES

       /etc/sysconfig/devlabel
	      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 it.

METHODOLOGY

       To determine the unique identifier associated with a SCSI device, devlabel uses the program /usr/bin/scsi_unique_id.  If this program  can-
       not 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 0.

       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 UUID.

       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

USAGE

       Hotpluggable storage devices which show themselves as SCSI devices internally (eg. USB, firewire, but not  PCMCIA)  should  have  carefully
       chosen  symlink	names  (eg.  /dev/smartcardreader) 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.

LIMITATIONS

       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 number (e.g. when /dev/sda6 is deleted, /dev/sda7 becomes /dev/sda6).  Currently IA-64 systems 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.

UUID NAMING CONVENTION

       UUIDs are prefaced with a tag to alert devlabel as to where the identifier came from.  Currently, devlabel supports  SCSI  firware  identi-
       fiers 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

AUTHOR

       Gary Lerhaupt (gary_lerhaupt@dell.com)

Version 0.4							   January 2003 						       DEVLABEL(8)