btrfs-progs/Documentation/btrfs-replace.asciidoc

btrfs-replace(8)
================

NAME
----
btrfs-replace - replace devices managed by btrfs with other device.

SYNOPSIS
--------
*btrfs replace* <subcommand> <args>

DESCRIPTION
-----------
*btrfs replace* is used to replace btrfs managed devices with other device.

SUBCOMMAND
----------
*cancel* <mount_point>::
Cancel a running device replace operation.

*start* [-Bfr] <srcdev>|<devid> <targetdev> <path>::
Replace device of a btrfs filesystem.
+
On a live filesystem, duplicate the data to the target device which
is currently stored on the source device.
If the source device is not available anymore, or if the -r option is set,
the data is built only using the RAID redundancy mechanisms.
After completion of the operation, the source device is removed from the
filesystem.
If the <srcdev> is a numerical value, it is assumed to be the device id
of the filesystem which is mounted at <path>, otherwise it is
the path to the source device. If the source device is disconnected,
from the system, you have to use the devid parameter format.
The <targetdev> needs to be same size or larger than the <srcdev>.
+
NOTE: the filesystem has to be resized to fully take advantage of a
larger target device; this can be achieved with
`btrfs filesystem resize <devid>:max /path`
+
`Options`
+
-r::::
only read from <srcdev> if no other zero-defect mirror exists.
(enable this if your drive has lots of read errors, the access would be very
slow)
-f::::
force using and overwriting <targetdev> even if it looks like
it contains a valid btrfs filesystem.
+
A valid filesystem is assumed if a btrfs superblock is found which contains a
correct checksum. Devices that are currently mounted are
never allowed to be used as the <targetdev>.
+
-B::::
no background replace.

*status* [-1] <mount_point>::
Print status and progress information of a running device replace operation.
+
`Options`
+
-1::::
print once instead of print continuously until the replace
operation finishes (or is cancelled)


EXAMPLES
--------

Replacing an online drive with a bigger one
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Given the filesystem:

----
Label: 'MyVault'  uuid: ae20903e-b72d-49ba-b944-901fc6d888a1
	Total devices 2 FS bytes used 1TiB
	devid    1 size 1TiB used 500.00GiB path /dev/sda
	devid    2 size 1TiB used 500.00GiB path /dev/sdb
----

In order to replace '/dev/sda' ('devid 1') with a bigger drive located at
'/dev/sdc' you would run the following:

[source,shell]
----
btrfs replace start 1 /dev/sdc /mnt/my-vault/
----

You can monitor progress by:

[source,shell]
----
btrfs replace status /mnt/my-vault/
----

After the replacement is complete, as per the docs at `btrfs-filesystem`(8) in
order to use the entire storage space of the new drive you need to run:

[source,shell]
----
btrfs filesystem resize 1:max /mnt/my-vault/
----

EXIT STATUS
-----------
*btrfs replace* returns a zero exit status if it succeeds. Non zero is
returned in case of failure.

AVAILABILITY
------------
*btrfs* is part of btrfs-progs.
Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
further details.

SEE ALSO
--------
`mkfs.btrfs`(8),
`btrfs-device`(8),
`btrfs-filesystem`(8),