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

     gconcat - disk concatenation control utility

     gconcat create [-v] name prov prov [prov [...]]
     gconcat destroy [-fv] name [name [...]]
     gconcat label [-hv] name prov prov [prov [...]]
     gconcat stop [-fv] name [name [...]]
     gconcat clear [-v] prov [prov [...]]
     gconcat dump prov [prov [...]]
     gconcat list [name [...]]
     gconcat load [-v]
     gconcat unload [-v]

     The gconcat utility is used for device concatenation configuration.  The
     concatenation can be configured using two different methods: ``manual''
     or ``automatic''.  When using the ``manual'' method, no metadata are
     stored on the devices, so the concatenated device has to be configured by
     hand every time it is needed.  The ``automatic'' method uses on-disk
     metadata to detect devices.  Once devices are labeled, they will be
     automatically detected and configured.

     The first argument to gconcat indicates an action to be performed:

     create       Concatenate the given devices with specified name.  This is
                  the ``manual'' method.  The kernel module geom_concat.ko
                  will be loaded if it is not loaded already.

     label        Concatenate the given devices with the specified name.  This
                  is the ``automatic'' method, where metadata are stored in
                  every device's last sector.  The kernel module
                  geom_concat.ko will be loaded if it is not loaded already.

     stop         Turn off existing concatenate device by its name.  This
                  command does not touch on-disk metadata!

     destroy      Same as stop.

     clear        Clear metadata on the given devices.

     dump         Dump metadata stored on the given devices.

     list         List all or the given currently configured devices.

     load         Load geom_concat.ko kernel module.

     unload       Unload geom_concat.ko kernel module.

     Additional options:

     -f      Force the removal of the specified concatenated device.

     -h      Hardcode providers' names in metadata.

     -v      Be more verbose.

     The following sysctl(8) variables can be used to control the behavior of
     the CONCAT GEOM class.  The default value is shown next to each variable.

     kern.geom.concat.debug: 0
             Debug level of the CONCAT GEOM class.  This can be set to a
             number between 0 and 3, both included.  If set to 0 minimal debug
             information is printed, and if set to 3 the maximum amount of
             debug information in printed.

     The following example shows how to configure four disks for automatic
     concatenation, create a file system on it, and mount it:

           gconcat label -v data /dev/da0 /dev/da1 /dev/da2 /dev/da3
           newfs /dev/concat/data
           mount /dev/concat/data /mnt
           umount /mnt
           gconcat stop data
           gconcat unload

     Exit status is 0 on success, and 1 if the command fails.

     geom(4), loader.conf(5), geom(8), mount(8), newfs(8), sysctl(8),
     umount(8), vinum(8)

     The gconcat utility appeared in FreeBSD 5.3.

     Pawel Jakub Dawidek <>

FreeBSD 11.0-PRERELEASE          May 21, 2004          FreeBSD 11.0-PRERELEASE


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