Manpage/btrfstune

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=btrfstune(8) manual page=
 
 
{{GeneratedManpage
 
{{GeneratedManpage
 
|name=btrfstune}}
 
|name=btrfstune}}
 
==NAME==
 
btrfstune - tune various filesystem parameters
 
 
==SYNOPSIS==
 
 
<p><b>btrfstune</b> [options] <em>&lt;device&gt;</em> [<em>&lt;device&gt;</em>&#8230;]</p>
 
==DESCRIPTION==
 
 
<p><b>btrfstune</b> can be used to enable, disable or set various filesystem
 
parameters. The filesystem must be unmounted.</p>
 
<p>The common usecase is to enable features that were not enabled at mkfs time.
 
Please make sure that you have kernel support for the features.  You can find a
 
complete list of features and kernel version of their introduction at
 
https://btrfs.wiki.kernel.org/index.php/Changelog#By_feature .  Also, the
 
manual page [[Manpage/mkfs.btrfs|mkfs.btrfs(8)]] contains more details about the features.</p>
 
<p>Some of the features could be enabled on a mounted filesystem. Please refer to
 
the respective section in [[Manpage/btrfs|btrfs(5)]].</p>
 
==OPTIONS==
 
 
<dl>
 
<dt>
 
-S <em>&lt;0|1&gt;</em>
 
<dd>
 
<p>
 
Enable seeding on a given device. Value 1 will enable seeding, 0 will disable it.<br/>
 
A seeding filesystem is forced to be mounted read-only. A new device can be added
 
to the filesystem and will capture all writes keeping the seeding device intact.
 
</p>
 
 
<dt>
 
-r
 
<dd>
 
<p>
 
(since kernel: 3.7)
 
</p>
 
<p>Enable extended inode refs (hardlink limit per file in a directory is 65536),
 
enabled by mkfs feature <em>extref</em>.</p>
 
 
<dt>
 
-x
 
<dd>
 
<p>
 
(since kernel: 3.10)
 
</p>
 
<p>Enable skinny metadata extent refs (more efficient representation of extents),
 
enabled by mkfs feature <em>skinny-metadata</em>.</p>
 
<p>All newly created extents will use the new representation. To completely switch
 
the entire filesystem, run a full balance of the metadata. Please refer to
 
[[Manpage/btrfs-balance|btrfs-balance(8)]].</p>
 
 
<dt>
 
-n
 
<dd>
 
<p>
 
(since kernel: 3.14)
 
</p>
 
<p>Enable no-holes feature (more efficient representation of file holes), enabled
 
by mkfs feature <em>no-holes</em>.</p>
 
 
<dt>
 
-f
 
<dd>
 
<p>
 
Allow dangerous changes, e.g. clear the seeding flag or change fsid. Make sure
 
that you are aware of the dangers.
 
</p>
 
 
<dt>
 
-u
 
<dd>
 
<p>
 
Change fsid to a randomly generated UUID or continue previous fsid change
 
operation in case it was interrupted.
 
</p>
 
 
<dt>
 
-U <em>&lt;UUID&gt;</em>
 
<dd>
 
<p>
 
Change fsid to <em>UUID</em>.
 
</p>
 
<p>The <em>UUID</em> should be a 36 bytes string in [http://man7.org/linux/man-pages/man3/printf.3.html printf(3)] format
 
<em>"%08x-%04x-%04x-%04x-%012x"</em>.
 
If there is a previous unfinished fsid change, it will continue only if the
 
<em>UUID</em> matches the unfinished one or if you use the option <em>-u</em>.</p>
 
 
</dl>
 
<blockquote><b>Warning:</b>
 
Cancelling or interrupting a UUID change operation will make the
 
filesystem temporarily unmountable.  To fix it, rerun <em>btrfstune -u</em> to restore
 
the UUID and let it complete.</blockquote>
 
<blockquote><b>Warning:</b>
 
Clearing the seeding flag on a device may be dangerous.
 
If a previously-seeding device is changed, all filesystems that used that
 
device will become unmountable. Setting the seeding flag back will not fix
 
that.<br/>
 
A valid usecase is <em>seeding device as a base image</em>. Clear the seeding
 
flag, update the filesystem and make it seeding again, provided that it&#8217;s OK
 
to throw away all filesystems built on top of the previous base.</blockquote>
 
==EXIT STATUS==
 
 
<p><b>btrfstune</b> returns 0 if no error happened, 1 otherwise.</p>
 
==COMPATIBILITY NOTE==
 
 
<p>This tool exists for historical reasons but is still in use today.  The
 
functionality is about to be merged to the main tool someday and <b>btrfstune</b>
 
will become deprecated and removed afterwards.</p>
 
==SEE ALSO==
 
 
<p>[[Manpage/btrfs|btrfs(5)]],
 
[[Manpage/btrfs-balance|btrfs-balance(8)]],
 
[[Manpage/mkfs.btrfs|mkfs.btrfs(8)]]</p>
 
[[Category:Manpage]]
 

Latest revision as of 12:34, 12 January 2022

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