1BTRFS-FILESYSTEM(8) Btrfs Manual BTRFS-FILESYSTEM(8)
2
6 btrfs-filesystem - command group of btrfs that usually work on the
7 whole filesystem
8
10 btrfs filesystem <subcommand> <args>
11
13 btrfs filesystem is used to perform several whole filesystem level
14 tasks, including all the regular filesystem operations like resizing,
15 space stats, label setting/getting, and defragmentation. There are
16 other whole filesystem taks like scrub or balance that are grouped in
17 separate commands.
18
20 df [options] <path>
21 Show a terse summary information about allocation of block group
22 types of a given mount point. The original purpose of this command
23 was a debugging helper. The output needs to be further interpreted
24 and is not suitable for quick overview.
25 An example with description:
27 · device size: 1.9TiB, one device, no RAID
29 · filesystem size: 1.9TiB
31 · created with: mkfs.btrfs -d single -m single
33 $ btrfs filesystem df /path
35 Data, single: total=1.15TiB, used=1.13TiB
36 System, single: total=32.00MiB, used=144.00KiB
37 Metadata, single: total=12.00GiB, used=6.45GiB
38 GlobalReserve, single: total=512.00MiB, used=0.00B
39 · Data, System and Metadata are separate block group types.
41 GlobalReserve is an artificial and internal emergency space,
42 see below.
43 · single — the allocation profile, defined at mkfs time
45 · total — sum of space reserved for all allocation profiles of
47 the given type, ie. all Data/single. Note that it’s not total
48 size of filesystem.
49 · used — sum of used space of the above, ie. file extents,
51 metadata blocks
52 GlobalReserve is an artificial and internal emergency space. It is
54 used eg. when the filesystem is full. Its total size is dynamic
55 based on the filesystem size, usually not larger than 512MiB, used
56 may fluctuate.
57 The global block reserve is accounted within Metadata. In case the
59 filesystem metadata are exhausted, GlobalReserve/total +
60 Metadata/used = Metadata/total.
61 Options
63 -b|--raw
65 raw numbers in bytes, without the B suffix
66 -h|--human-readable
68 print human friendly numbers, base 1024, this is the default
69 -H
71 print human friendly numbers, base 1000
72 --iec
74 select the 1024 base for the following options, according to
75 the IEC standard
76 --si
78 select the 1000 base for the following options, according to
79 the SI standard
80 -k|--kbytes
82 show sizes in KiB, or kB with --si
83 -m|--mbytes
85 show sizes in MiB, or MB with --si
86 -g|--gbytes
88 show sizes in GiB, or GB with --si
89 -t|--tbytes
91 show sizes in TiB, or TB with --si
92 If conflicting options are passed, the last one takes
94 precedence.
95 defragment [options] <file>|<dir> [<file>|<dir>...]
97 Defragment file data on a mounted filesystem. Requires kernel
98 2.6.33 and newer.
99 If -r is passed, files in dir will be defragmented recursively. The
101 start position and the number of bytes to defragment can be
102 specified by start and length using -s and -l options below.
103 Extents bigger than value given by -t will be skipped, otherwise
104 this value is used as a target extent size, but is only advisory
105 and may not be reached if the free space is too fragmented. Use 0
106 to take the kernel default, which is 256kB but may change in the
107 future. You can also turn on compression in defragment operations.
108 Warning
110 Defragmenting with Linux kernel versions < 3.9 or ≥ 3.14-rc2 as
111 well as with Linux stable kernel versions ≥ 3.10.31, ≥ 3.12.12
112 or ≥ 3.13.4 will break up the ref-links of COW data (for
113 example files copied with cp --reflink, snapshots or
114 de-duplicated data). This may cause considerable increase of
115 space usage depending on the broken up ref-links.
116 Note
118 Directory arguments without -r do not defragment files
119 recursively but will defragment certain internal trees (extent
120 tree and the subvolume tree). This has been confusing and could
121 be removed in the future.
122 For start, len, size it is possible to append units designator:
123 'K', 'M', 'G', 'T', 'P', or 'E', which represent KiB, MiB, GiB,
124 TiB, PiB, or EiB, respectively (case does not matter).
125 Options
127 -v
129 be verbose, print file names as they’re submitted for
130 defragmentation
131 -c[<algo>]
133 compress file contents while defragmenting. Optional argument
134 selects the compression algorithm, zlib (default) or lzo.
135 Currently it’s not possible to select no compression. See also
136 section EXAMPLES.
137 -r
139 defragment files recursively in given directories
140 -f
142 flush data for each file before going to the next file.
143 This will limit the amount of dirty data to current file,
145 otherwise the amount cumulates from several files and will
146 increase system load. This can also lead to ENOSPC if there’s
147 too much dirty data to write and it’s not possible to make the
148 reservations for the new data (ie. how the COW design works).
149 -s <start>[kKmMgGtTpPeE]
151 defragmentation will start from the given offset, default is
152 beginning of a file
153 -l <len>[kKmMgGtTpPeE]
155 defragment only up to len bytes, default is the file size
156 -t <size>[kKmMgGtTpPeE]
158 target extent size, do not touch extents bigger than size,
159 default: 32M
160 The value is only advisory and the final size of the extents
162 may differ, depending on the state of the free space and
163 fragmentation or other internal logic. Reasonable values are
164 from tens to hundreds of megabytes.
165 du [options] <path> [<path>..]
167 Calculate disk usage of the target files using FIEMAP. For
168 individual files, it will report a count of total bytes, and
169 exclusive (not shared) bytes. We also calculate a set shared value
170 which is described below.
171 Each argument to btrfs fi du will have a set shared value
173 calculated for it. We define each set as those files found by a
174 recursive search of an argument. The set shared value then is a sum
175 of all shared space referenced by the set.
176 set shared takes into account overlapping shared extents, hence it
178 isn’t as simple as adding up shared extents.
179 Options
181 -s|--summarize
183 display only a total for each argument
184 --raw
186 raw numbers in bytes, without the B suffix.
187 --human-readable
189 print human friendly numbers, base 1024, this is the default
190 --iec
192 select the 1024 base for the following options, according to
193 the IEC standard.
194 --si
196 select the 1000 base for the following options, according to
197 the SI standard.
198 --kbytes
200 show sizes in KiB, or kB with --si.
201 --mbytes
203 show sizes in MiB, or MB with --si.
204 --gbytes
206 show sizes in GiB, or GB with --si.
207 --tbytes
209 show sizes in TiB, or TB with --si.
210 label [<dev>|<mountpoint>] [<newlabel>]
212 Show or update the label of a filesystem. This works on a mounted
213 filesystem or a filesystem image.
214 The newlabel argument is optional. Current label is printed if the
216 the argument is omitted.
217 Note
219 the maximum allowable length shall be less than 256 chars and
220 must not contain a newline. The trailing newline is stripped
221 automatically.
222 resize [<devid>:][+/-]<size>[kKmMgGtTpPeE]|[<devid>:]max <path>
224 Resize a mounted filesystem identified by path. A particular device
225 can be resized by specifying a devid.
226 Warning
228 If path is a file containing a BTRFS image then resize does not
229 work as expected and does not resize the image. This would
230 resize the underlying filesystem instead.
231 The devid can be found in the output of btrfs filesystem show and
232 defaults to 1 if not specified. The size parameter specifies the
233 new size of the filesystem. If the prefix + or - is present the
234 size is increased or decreased by the quantity size. If no units
235 are specified, bytes are assumed for size. Optionally, the size
236 parameter may be suffixed by one of the following units
237 designators: 'K', 'M', 'G', 'T', 'P', or 'E', which represent KiB,
238 MiB, GiB, TiB, PiB, or EiB, respectively (case does not matter).
239 If max is passed, the filesystem will occupy all available space on
241 the device respecting devid (remember, devid 1 by default).
242 The resize command does not manipulate the size of underlying
244 partition. If you wish to enlarge/reduce a filesystem, you must
245 make sure you can expand the partition before enlarging the
246 filesystem and shrink the partition after reducing the size of the
247 filesystem. This can done using fdisk(8) or parted(8) to delete the
248 existing partition and recreate it with the new desired size. When
249 recreating the partition make sure to use the same starting
250 partition offset as before.
251 Growing is usually instant as it only updates the size. However,
253 shrinking could take a long time if there are data in the device
254 area that’s beyond the new end. Relocation of the data takes time.
255 See also section EXAMPLES.
257 show [options] [<path>|<uuid>|<device>|<label>]
259 Show the btrfs filesystem with some additional info about devices
260 and space allocation.
261 If no option none of path/uuid/device/label is passed, information
263 about all the BTRFS filesystems is shown, both mounted and
264 unmounted.
265 Options
267 -m|--mounted
269 probe kernel for mounted BTRFS filesystems
270 -d|--all-devices
272 scan all devices under /dev, otherwise the devices list is
273 extracted from the /proc/partitions file. This is a fallback
274 option if there’s no device node manager (like udev) available
275 in the system.
276 --raw
278 raw numbers in bytes, without the B suffix
279 --human-readable
281 print human friendly numbers, base 1024, this is the default
282 --iec
284 select the 1024 base for the following options, according to
285 the IEC standard
286 --si
288 select the 1000 base for the following options, according to
289 the SI standard
290 --kbytes
292 show sizes in KiB, or kB with --si
293 --mbytes
295 show sizes in MiB, or MB with --si
296 --gbytes
298 show sizes in GiB, or GB with --si
299 --tbytes
301 show sizes in TiB, or TB with --si
302 sync <path>
304 Force a sync of the filesystem at path. This is done via a special
305 ioctl and will also trigger cleaning of deleted subvolumes. Besides
306 that it’s equivalent to the sync(1) command.
307 usage [options] <path> [<path>...]
309 Show detailed information about internal filesystem usage. This is
310 supposed to replace the btrfs filesystem df command in the long
311 run.
312 The level of detail can differ if the command is run under a
314 regular or the root user (due to use of restricted ioctl). For both
315 there’s a summary section with information about space usage:
316 $ btrfs fi usage /path
318 WARNING: cannot read detailed chunk info, RAID5/6 numbers will be incorrect, run as root
319 Overall:
320 Device size: 1.82TiB
321 Device allocated: 1.17TiB
322 Device unallocated: 669.99GiB
323 Device missing: 0.00B
324 Used: 1.14TiB
325 Free (estimated): 692.57GiB (min: 692.57GiB)
326 Data ratio: 1.00
327 Metadata ratio: 1.00
328 Global reserve: 512.00MiB (used: 0.00B)
329 The root user will also see stats broken down by block group types:
331 Data,single: Size:1.15TiB, Used:1.13TiB
333 /dev/sdb 1.15TiB
334 Metadata,single: Size:12.00GiB, Used:6.45GiB
336 /dev/sdb 12.00GiB
337 System,single: Size:32.00MiB, Used:144.00KiB
339 /dev/sdb 32.00MiB
340 Unallocated:
342 /dev/sdb 669.99GiB
343 Options
345 -b|--raw
347 raw numbers in bytes, without the B suffix
348 -h|--human-readable
350 print human friendly numbers, base 1024, this is the default
351 -H
353 print human friendly numbers, base 1000
354 --iec
356 select the 1024 base for the following options, according to
357 the IEC standard
358 --si
360 select the 1000 base for the following options, according to
361 the SI standard
362 -k|--kbytes
364 show sizes in KiB, or kB with --si
365 -m|--mbytes
367 show sizes in MiB, or MB with --si
368 -g|--gbytes
370 show sizes in GiB, or GB with --si
371 -t|--tbytes
373 show sizes in TiB, or TB with --si
374 -T
376 show data in tabular format
377 If conflicting options are passed, the last one takes
379 precedence.
380
382 $ btrfs filesystem defrag -v -r dir/
383 Recursively defragment files under dir/, print files as they are
385 processed. The file names will be printed in batches, similarly the
386 amount of data triggered by defragmentation will be proportional to
387 last N printed files. The system dirty memory throttling will slow down
388 the defragmentation but there can still be a lot of IO load and the
389 system may stall for a moment.
390 $ btrfs filesystem defrag -v -r -f dir/
392 Recursively defragment files under dir/, be verbose and wait until all
394 blocks are flushed before processing next file. You can note slower
395 progress of the output and lower IO load (proportional to currently
396 defragmented file).
397 $ btrfs filesystem defrag -v -r -f -clzo dir/
399 Recursively defragment files under dir/, be verbose, wait until all
401 blocks are flushed and force file compression.
402 $ btrfs filesystem defrag -v -r -t 64M dir/
404 Recursively defragment files under dir/, be verbose and try to merge
406 extents to be about 64MiB. As stated above, the success rate depends on
407 actual free space fragmentation and the final result is not guaranteed
408 to meet the target even if run repeatedly.
409 $ btrfs filesystem resize -1G /path
411 $ btrfs filesystem resize 1:-1G /path
413 Shrink size of the filesystem’s device id 1 by 1GiB. The first syntax
415 expects a device with id 1 to exist, otherwise fails. The second is
416 equivalent and more explicit. For a single-device filesystem it’s
417 typically not necessary to specify the devid though.
418 $ btrfs filesystem resize max /path
420 $ btrfs filesystem resize 1:max /path
422 Let’s assume that devid 1 exists, the filesystem does not occupy the
424 whole block device, eg. it has been enlarged and we wan the grow the
425 filesystem. Simply using max as size we will achieve that.
426 Note
428 There are two ways to minimize the filesystem on a given device.
429 The btrfs inspect-internal min-dev-size command, or iteratively
430 shrink in steps.
431
433 btrfs filesystem returns a zero exit status if it succeeds. Non zero is
434 returned in case of failure.
435
437 btrfs is part of btrfs-progs. Please refer to the btrfs wiki
438 http://btrfs.wiki.kernel.org for further details.
439
441 mkfs.btrfs(8),
442Btrfs v4.9.1 08/06/2017 BTRFS-FILESYSTEM(8)