btrfs-convert(8)
NAME
btrfs-convert - convert from ext2/3/4 filesystem to btrfs in-place
SYNOPSIS
btrfs-convert [options] <device>
DESCRIPTION
btrfs-convert is used to convert existing ext2/3/4 filesystem image to
a btrfs filesystem in-place. The original filesystem image is
accessible subvolume named ext2_saved as file image.
Warning
If you are going to perform rollback to ext2/3/4, you should not
execute btrfs balance command on the converted filesystem. This
will change the extent layout and make btrfs-convert unable to
rollback.
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.
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.
Due to different constraints, it's possible to convert only filesystem
that have supported data block size (ie. the same that would be valid
for mkfs.btrfs). This is typically the system page size (4KiB on x86_64
machines).
REMOVE THE ORIGINAL FILESYSTEM METADATA
By removing the ext2_saved subvolume, all metadata of the original
filesystem will be removed:
# btrfs subvolume delete /mnt/ext2_saved
At this point it's not possible to do rollback. The filesystem is
usable but may be impacted by the fragmentation inherited from the
original filesystem.
MAKE FILE DATA MORE CONTIGUOUS
An optional but recommended step is to run defragmentation on the
entire filesystem. This will attempt to make file extents more
contiguous.
# btrfs filesystem defrag -v -r -f -t 32M /mnt/btrfs
Verbose recursive defragmentation (-v, -r), flush data per-file (-f)
with target extent size 32MiB (-t).
ATTEMPT TO MAKE BTRFS METADATA MORE COMPACT
Optional but recommended step.
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.
Note that balance operation takes a lot of time, please see also
btrfs-balance(8).
# btrfs balance start -m /mnt/btrfs
OPTIONS
-d|--no-datasum
disable data checksum calculations and set the NODATASUM file flag,
this can speed up the conversion
-i|--no-xattr
ignore xattrs and ACLs of files
-n|--no-inline
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
-N|--nodesize <SIZE>
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 mkfs.btrfs(8) for more details.
-r|--rollback
rollback to the original ext2/3/4 filesystem if possible
-l|--label <LABEL>
set filesystem label during conversion
-L|--copy-label
use label from the converted filesystem
-O|--features <feature1>[,<feature2>...]
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 ^. Description of the features is in section FILESYSTEM
FEATURES of mkfs.btrfs(8).
To see all available features that btrfs-convert supports run:
btrfs-convert -O list-all
-p|--progress
show progress of conversion (a heartbeat indicator and number of
inodes processed), on by default
--no-progress
disable progress and show only the main phases of conversion
EXIT STATUS
btrfs-convert will return 0 if no error happened. If any problems happened, 1 will be returned.
SEE ALSO
mkfs.btrfs(8)
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
