CCDCONFIG(8)            FreeBSD 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

     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 second
     slice of /dev/da8 is mirrored with the third 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/ada0s1 /dev/ada0s2

     When you create a new ccd disk you generally want to partition it using
     gpart(8) it before doing anything else.  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
     mirror.  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 graid(8) or zfs(8).

SEE ALSO

     dd(1), ccd(4), gpart(8), graid(8), rc(8), zfs(8)

HISTORY

     The ccdconfig utility first appeared in NetBSD 1.1.

FreeBSD 15.1-STABLE-HBSD       January 23, 2025                   CCDCONFIG(8)