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

NAME

     gconcat - disk concatenation control utility

SYNOPSIS

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

DESCRIPTION

     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.

              Additional options include:

              -h
                 Hardcode providers' names in metadata.

     append   Append a new device to the end of an existing concatenate device
              with the specified name.

              If the existing device is using the "manual" method, the new
              device is simply appended as-is.

              If the existing device is using the "automatic" method, the
              device is appended persistently.  New gconcat metadata is
              written to all existing components, as well as to the newly
              added one.

              Additional options include:

              -h
                 Hardcode providers' names in metadata.

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

              Additional options include:

              -f
                 Stop the given device even if it is opened.

     destroy  Same as stop.

     clear    Clear metadata on the given devices.

     dump     Dump metadata stored on the given devices.

     list     See geom(8).

     status   See geom(8).

     load     See geom(8).

     unload   See geom(8).

     Additional options:

     -v      Be more verbose.

SYSCTL VARIABLES

     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 inclusive.  If set to 0 minimal debug
             information is printed, and if set to 3 the maximum amount of
             debug information is printed.

EXIT STATUS

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

EXAMPLES

     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

     Configure concatenated provider on one disk only.  Create file system.
     Add two more disks and extend existing file system.

           gconcat label data /dev/da0
           newfs /dev/concat/data
           gconcat label data /dev/da0 /dev/da1 /dev/da2
           growfs /dev/concat/data

SEE ALSO

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

HISTORY

     The gconcat utility appeared in FreeBSD 5.3.

AUTHORS

     Pawel Jakub Dawidek <pjd@FreeBSD.org>

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