ccdconfig man page on FreeBSD

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

NAME
     ccdconfig — configuration utility for the concatenated disk driver

SYNOPSIS
     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 ...]

DESCRIPTION
     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).

FILES
     /etc/ccd.conf  default ccd configuration file

EXAMPLES
     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.

RECOVERY
     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).

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

HISTORY
     The ccdconfig utility first appeared in NetBSD 1.0A.

BUGS
     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.

BSD				 July 17, 1995				   BSD
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