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CCDCONFIG(8)		FreeBSD	System Manager's Manual		  CCDCONFIG(8)

     ccdconfig -- configuration	utility	for the	concatenated disk driver

     ccdconfig [-cv] ccd ileave	[flags]	dev ...
     ccdconfig -C [-v] [-f config_file]
     ccdconfig -u [-v] ccd ...
     ccdconfig -U [-v] [-f config_file]
     ccdconfig -g [ccd ...]

     The ccdconfig utility is used to dynamically configure and	unconfigure
     concatenated disk devices,	or ccds.  For more information about the ccd,
     see ccd(4).

     The options are as	follows:

     -c	     Configure a ccd.  This is the default behavior of ccdconfig.

     -C	     Configure all ccd devices listed in the ccd configuration file.

     -f	config_file
	     When configuring or unconfiguring all devices, read the file
	     config_file instead of the	default	/etc/ccd.conf.

     -g	     Dump the current ccd configuration	in a format suitable for use
	     as	the ccd	configuration file.  If	no arguments are specified,
	     every configured ccd is dumped.  Otherwise, the configuration of
	     each listed ccd is	dumped.

     -u	     Unconfigure a ccd.

     -U	     Unconfigure all ccd devices listed	the ccd	configuration file.

     -v	     Cause ccdconfig to	be verbose.

     A ccd is described	on the command line and	in the ccd configuration file
     by	the name of the	ccd, the interleave factor, the	ccd configuration
     flags, and	a list of one or more devices.	The flags may be represented
     as	a decimal number, a hexadecimal	number,	a comma-separated list of
     strings, or the word ``none''.  The flags are as follows:

	   CCDF_UNIFORM	   0x02		   Use uniform interleave
	   CCDF_MIRROR	   0x04		   Support mirroring
	   CCDF_NO_OFFSET  0x08		   Do not use an offset
	   CCDF_LINUX	   0x0A		   Linux md(4) compatibility

     The format	in the configuration file appears exactly as if	it were
     entered on	the command line.  Note	that on	the command line and in	the
     configuration file, the flags argument is optional.

	   # /etc/ccd.conf
	   # Configuration file	for concatenated disk devices

	   # ccd	   ileave  flags   component devices
	   ccd0		   16	   none	   /dev/da2s1 /dev/da3s1

     The component devices need	to name	partitions of type FS_BSDFFS (or
     ``4.2BSD''	as shown by disklabel(8)).

     If	you want to use	the Linux md(4)	compatibility mode, please be sure to
     read the notes in ccd(4).

     /etc/ccd.conf  default ccd	configuration file

     A number of ccdconfig examples are	shown below.  The arguments passed to
     ccdconfig are exactly the same as you might place in the /etc/ccd.conf
     configuration file.  The first example creates a 4-disk stripe out	of
     four scsi disk partitions.	 The stripe uses a 64 sector interleave.  The
     second example is an example of a complex stripe/mirror combination.  It
     reads as a	two disk stripe	of da4 and da5 which is	mirrored to a two disk
     stripe of da6 and da7.  The last example is a simple mirror.  The 2nd
     slice of /dev/da8 is mirrored with	the 3rd	slice of /dev/da9 and assigned
     to	ccd0.

     # ccdconfig ccd0 64 none /dev/da0s1 /dev/da1s1 /dev/da2s1 /dev/da3s1
     # ccdconfig ccd0 128 CCDF_MIRROR /dev/da4 /dev/da5	/dev/da6 /dev/da7
     # ccdconfig ccd0 128 CCDF_MIRROR /dev/da8s2 /dev/da9s3

     The following are matching	commands in Linux and FreeBSD to create	a
     RAID-0 in Linux and read it from FreeBSD.

     # Create a	RAID-0 on Linux:
     mdadm --create --chunk=32 --level=0 --raid-devices=2 /dev/md0 \
	/dev/hda1 /dev/hdb1
     # Make the	RAID-0 just created available on FreeBSD:
     ccdconfig -c /dev/ccd0 32 linux /dev/ad0s1	/dev/ad0s2

     When you create a new ccd disk you	generally want to fdisk(8) and
     disklabel(8) it before doing anything else.  Once you create the initial
     label you can edit	it, adding additional partitions.  The label itself
     takes up the first	16 sectors of the ccd disk.  If	all you	are doing is
     creating file systems with	newfs, you do not have to worry	about this as
     newfs will	skip the label area.  However, if you intend to	dd(1) to or
     from a ccd	partition it is	usually	a good idea to construct the partition
     such that it does not overlap the label area.  For	example, if you	have A
     ccd disk with 10000 sectors you might create a 'd'	partition with offset
     16	and size 9984.

     # disklabel ccd0 >	/tmp/disklabel.ccd0
     # disklabel -Rr ccd0 /tmp/disklabel.ccd0
     # disklabel -e ccd0

     The disklabeling of a ccd disk is usually a one-time affair.  If you
     reboot the	machine	and reconfigure	the ccd	disk, the disklabel you	had
     created before will still be there	and not	require	reinitialization.
     Beware that changing any ccd parameters: interleave, flags, or the	device
     list making up the	ccd disk, will usually destroy any prior data on that
     ccd disk.	If this	occurs it is usually a good idea to reinitialize the
     label before [re]constructing your	ccd disk.

     An	error on a ccd disk is usually unrecoverable unless you	are using the
     mirroring option.	But mirroring has its own perils: It assumes that both
     copies of the data	at any given sector are	the same.  This	holds true
     until a write error occurs	or until you replace either side of the	mir-
     ror.  This	is a poor-man's	mirroring implementation.  It works well
     enough that if you	begin to get disk errors you should be able to backup
     the ccd disk, replace the broken hardware,	and then regenerate the	ccd
     disk.  If you need	more than this you should look into external hardware
     RAID SCSI boxes, RAID controllers (see GENERIC), or software RAID systems
     such as geom(8) and vinum(8).

     dd(1), ccd(4), disklabel(8), fdisk(8), rc(8), vinum(8)

     The ccdconfig utility first appeared in NetBSD 1.0A.

     The initial disklabel returned by ccd(4) specifies	only 3 partitions.
     One needs to change the number of partitions to 8 using ``disklabel -e''
     to	get the	usual BSD expectations.

FreeBSD	8.3			 July 17, 1995			   FreeBSD 8.3


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