BTRFS\-REPLACE

Section: Btrfs Manual (8)
Updated: 03/24/2021
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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 [options] <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.

--enqueue

: wait if there's another exclusive operation running, otherwise continue

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

Example 1. Replacing an online drive with a bigger one

Given the following filesystem mounted at /mnt/my-vault

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:

btrfs replace start 1 /dev/sdc /mnt/my-vault/

You can monitor progress via:

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:

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 m[blue]http://btrfs.wiki.kernel.orgm[] for further details.