'\" t
.\"     Title: btrfs-convert
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 09/22/2016
.\"    Manual: Btrfs Manual
.\"    Source: Btrfs v4.7.3
.\"  Language: English
.\"
.TH "BTRFS\-CONVERT" "8" "09/22/2016" "Btrfs v4\&.7\&.3" "Btrfs Manual"
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.SH "NAME"
btrfs-convert \- convert from ext2/3/4 filesystem to btrfs in\-place
.SH "SYNOPSIS"
.sp
\fBbtrfs\-convert\fR [options] \fI<device>\fR
.SH "DESCRIPTION"
.sp
\fBbtrfs\-convert\fR is used to convert existing ext2/3/4 filesystem image to a btrfs filesystem in\-place\&. The original filesystem image is accessible subvolume named \fIext2_saved\fR as file \fIimage\fR\&.
.if n \{\
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\fBWarning\fR
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If you are going to perform rollback to ext2/3/4, you should not execute \fBbtrfs balance\fR command on the converted filesystem\&. This will change the extent layout and make \fBbtrfs\-convert\fR unable to rollback\&.
.sp .5v
.RE
.sp
The conversion utilizes free space of the original filesystem\&. The exact estimate of the required space cannot be foretold\&. The final btrfs metadata might occupy several gigabytes on a hundreds\-gigabyte filesystem\&.
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If you decide not to rollback anymore, it is recommended to perform a few more steps to transform the btrfs filesystem to a more compact layout\&. The conversion inherits the original data block fragmentation and the metadata blocks are bound to the original free space layout\&.
.sp
Due to different constraints, it\(cqs possible to convert only filesystem that have supported data block size (ie\&. the same that would be valid for \fImkfs\&.btrfs\fR)\&. This is typically the system page size (4KiB on x86_64 machines)\&.
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\fBREMOVE THE ORIGINAL FILESYSTEM METADATA\fR
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By removing the \fIext2_saved\fR subvolume, all metadata of the original filesystem will be removed:
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# btrfs subvolume delete /mnt/ext2_saved
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.if n \{\
.RE
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At this point it\(cqs not possible to do rollback\&. The filesystem is usable but may be impacted by the fragmentation inherited from the original filesystem\&.
.sp
\fBMAKE FILE DATA MORE CONTIGUOUS\fR
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An optional but recommended step is to run defragmentation on the entire filesystem\&. This will attempt to make file extents more contiguous\&.
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.if n \{\
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# btrfs filesystem defrag \-v \-r \-f \-t 32M /mnt/btrfs
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.if n \{\
.RE
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Verbose recursive defragmentation (\fI\-v\fR, \fI\-r\fR), flush data per\-file (\fI\-f\fR) with target extent size 32MiB (\fI\-t\fR)\&.
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\fBATTEMPT TO MAKE BTRFS METADATA MORE COMPACT\fR
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Optional but recommended step\&.
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The metadata block groups after conversion may be smaller than the default size (256MiB or 1GiB)\&. Running a balance will attempt to merge the block groups\&. This depends on the free space layout (and fragmentation) and may fail due to lack of enough work space\&. This is a soft error leaving the filesystem usable but the block group layout may remain unchanged\&.
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Note that balance operation takes a lot of time, please see also \fBbtrfs\-balance\fR(8)\&.
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# btrfs balance start \-m /mnt/btrfs
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.SH "OPTIONS"
.PP
\-d|\-\-no\-datasum
.RS 4
disable data checksum calculations and set the NODATASUM file flag, this can speed up the conversion
.RE
.PP
\-i|\-\-no\-xattr
.RS 4
ignore xattrs and ACLs of files
.RE
.PP
\-n|\-\-no\-inline
.RS 4
disable inlining of small files to metadata blocks, this will decrease the metadata consumption and may help to convert a filesystem with low free space
.RE
.PP
\-N|\-\-nodesize \fI<SIZE>\fR
.RS 4
set filesystem nodesize, the tree block size in which btrfs stores its metadata\&. The default value is 16KB (16384) or the page size, whichever is bigger\&. Must be a multiple of the sectorsize, but not larger than 65536\&. See
\fBmkfs\&.btrfs\fR(8) for more details\&.
.RE
.PP
\-r|\-\-rollback
.RS 4
rollback to the original ext2/3/4 filesystem if possible
.RE
.PP
\-l|\-\-label \fI<LABEL>\fR
.RS 4
set filesystem label during conversion
.RE
.PP
\-L|\-\-copy\-label
.RS 4
use label from the converted filesystem
.RE
.PP
\-O|\-\-features \fI<feature1>\fR[,\fI<feature2>\fR\&...]
.RS 4
A list of filesystem features turned on at conversion time\&. Not all features are supported by old kernels\&. To disable a feature, prefix it with
\fI^\fR\&. Description of the features is in section
\fIFILESYSTEM FEATURES\fR
of
\fBmkfs\&.btrfs\fR(8)\&.
.sp
To see all available features that btrfs\-convert supports run:
.sp
\fBbtrfs\-convert \-O list\-all\fR
.RE
.PP
\-p|\-\-progress
.RS 4
show progress of conversion (a heartbeat indicator and number of inodes processed), on by default
.RE
.PP
\-\-no\-progress
.RS 4
disable progress and show only the main phases of conversion
.RE
.SH "EXIT STATUS"
.sp
\fBbtrfs\-convert\fR will return 0 if no error happened\&. If any problems happened, 1 will be returned\&.
.SH "SEE ALSO"
.sp
\fBmkfs\&.btrfs\fR(8)