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