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NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | NOTES | COLOPHON |
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CLONETAB(5) clonetab CLONETAB(5)
clonetab - Configuration for dm-clone block devices
/etc/clonetab
The /etc/clonetab file describes dm-clone block devices that are
set up during system boot.
Empty lines and lines starting with the "#" character are ignored.
Each of the remaining lines describes one dm-clone device. Fields
are delimited by white space.
Each line is in the form
name source-device destination-device metadata-device [options]
The first four fields are mandatory, the fifth is optional.
The five fields of /etc/clonetab are defined as follows:
1. The first field contains the name of the resulting dm-clone
device; its block device is set up below /dev/mapper/.
2. The second field contains a path to the read-only source block
device. This is the device whose data is cloned to the
destination device. Reads to regions not yet hydrated are
served directly from this device.
3. The third field contains a path to the writable destination
block device. The source device's data is copied here in the
background. It must be at least as large as the source device.
4. The fourth field contains a path to the metadata block device.
This small device tracks which regions of the destination have
been hydrated and is managed exclusively by dm-clone.
5. The fifth field, if present, contains comma-separated
"key=value" options. The following option is supported:
region-size=BYTES
Controls the granularity of background hydration copying —
how much data is copied at a time. Region size is
specified in bytes (standard suffixes like "K", "M", "G"
are supported), and must correspond to a power of two
between 4 KiB and 1 GiB. For example, "region-size=4K" or
"region-size=4096" sets a 4 KiB region size.
One region is the atomic unit dm-clone tracks: it is
either fully hydrated (copied to the destination) or not,
never partially. If a copy is interrupted mid-region, that
whole region is retried from scratch on next boot. Smaller
regions mean finer progress tracking; larger regions
reduce metadata overhead. Defaults to "4K". For
background, see dm-clone kernel documentation[1].
Added in version 262.
If no options are needed, the field may be omitted entirely or
"-" may be used as a placeholder.
At early boot and when the system manager configuration is
reloaded, this file is translated into native systemd units by
systemd-clonesetup-generator(8).
Example 1. Simple clone without options
Clone a source device to a destination, using a separate metadata
device:
mydevice /dev/sdb /dev/sdc /dev/sdd
Example 2. Clone with custom region size
Clone a source device to a destination with a custom region size
of 8 KiB:
mydevice /dev/sdb /dev/sdc /dev/sdd region-size=8K
systemd(1), systemd-clonesetup-generator(8), dmsetup(8)
1. dm-clone kernel documentation
https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/dm-clone.html
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2026-08-04. (At that
time, the date of the most recent commit that was found in the
repository was 2026-08-03.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 262~devel CLONETAB(5)
Pages that refer to this page: systemd.directives(7), systemd.index(7), systemd-clonesetup(8), systemd-clonesetup-generator(8)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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