BTRFS-INSPECT-INTERNAL(8) BTRFS BTRFS-INSPECT-INTERNAL(8)

btrfs-inspect-internal - query various internal information

btrfs inspect-internal <subcommand> <args>

This command group provides an interface to query internal information. The functionality ranges from a simple UI to an ioctl or a more complex query that assembles the result from several internal structures. The latter usually requires calls to privileged ioctls.

Show btrfs superblock information stored on given devices in textual form. By default the first superblock is printed, more details about all copies or additional backup data can be printed.

Besides verification of the filesystem signature, there are no other sanity checks. The superblock checksum status is reported, the device item and filesystem UUIDs are checked and reported.

NOTE:

The meaning of option -s has changed in version 4.8 to be consistent with other tools to specify superblock copy rather the offset. The old way still works, but prints a warning. Please update your scripts to use --bytenr instead. The option -i has been deprecated.


Options

print full superblock information, including the system chunk array and backup roots
print information about all present superblock copies (cannot be used together with -s option)

(deprecated since 4.8, same behaviour as --super)
specify offset to a superblock in a non-standard location at bytenr, useful for debugging (disables the -f option)

If there are multiple options specified, only the last one applies.


attempt to print the superblock even if a valid BTRFS signature is not found; the result may be completely wrong if the data does not resemble a superblock
(see compatibility note above)

specify which mirror to print, valid values are 0, 1 and 2 and the superblock must be present on the device with a valid signature, can be used together with --force


Dump tree structures from a given device in textual form, expand keys to human readable equivalents where possible. This is useful for analyzing filesystem state or inconsistencies and has a positive educational effect on understanding the internal filesystem structure.

NOTE:

By default contains file names, consider that if you're asked to send the dump for analysis and use --hide-names eventually. Does not contain file data.


Special characters in file names, xattr names and values are escaped, in the C style like \n and octal encoding \NNN.

Options

print only extent-related information: extent and device trees
print only device-related information: tree root, chunk and device trees
print only short root node information, i.e. the root tree keys
same as --roots plus print backup root info, i.e. the backup root keys and the respective tree root block offset
print only the uuid tree information, empty output if the tree does not exist

print info of the specified block only, can be specified multiple times
use with -b, print all children tree blocks of <block_num>
(default up to 5.2)

use depth-first search to print trees, the nodes and leaves are intermixed in the output

(default since 5.3)

use breadth-first search to print trees, the nodes are printed before all leaves

print a placeholder HIDDEN instead of various names, useful for developers to inspect the dump while keeping potentially sensitive information hidden

This is:

  • directory entries (files, directories, subvolumes)
  • default subvolume
  • extended attributes (name, value)
  • hardlink names (if stored inside another item or as extended references in standalone items)

NOTE:

Lengths are not hidden because they can be calculated from the item size anyway.


print b-tree node checksums stored in headers (metadata)
print checksums stored in checksum items (data)
do not automatically scan the system for other devices from the same filesystem, only use the devices provided as the arguments
print only the tree with the specified ID, where the ID can be numerical or common name in a flexible human readable form

The tree id name recognition rules:

  • case does not matter
  • the C source definition, e.g. BTRFS_ROOT_TREE_OBJECTID
  • short forms without BTRFS_ prefix, without _TREE and _OBJECTID suffix, e.g. ROOT_TREE, ROOT
  • convenience aliases, e.g. DEVICE for the DEV tree, CHECKSUM for CSUM
  • unrecognized ID is an error


(needs root privileges)

resolve paths to all files with given inode number ino in a given subvolume at path, i.e. all hardlinks

Options

(deprecated) alias for global -v option

(needs root privileges)

resolve paths to all files at given logical address in the linear filesystem space

Options

skip the path resolving and print the inodes instead
ignore offsets, find all references to an extent instead of a single block. Requires kernel support for the V2 ioctl (added in 4.15). The results might need further processing to filter out unwanted extents by the offset that is supposed to be obtained by other means.
set internal buffer for storing the file names to bufsize, default is 64KiB, maximum 16MiB. Buffer sizes over 64Kib require kernel support for the V2 ioctl (added in 4.15).
(deprecated) alias for global -v option

(needs root privileges)

Enumerate chunks on all devices. The chunks represent the physical range on devices (not to be confused with block groups that represent the logical ranges, but the terms are often used interchangeably).

Example output:

Devid PNumber      Type/profile    PStart    Length      PEnd LNumber    LStart Usage%
----- ------- ----------------- --------- --------- --------- ------- --------- ------
    1       1       Data/single   1.00MiB  84.00MiB  85.00MiB      68 191.60GiB  62.77
    1       2     System/DUP     85.00MiB  32.00MiB 117.00MiB      39 140.17GiB   0.05
    1       3     System/DUP    117.00MiB  32.00MiB 149.00MiB      40 140.17GiB   0.05
    1       4   Metadata/DUP    149.00MiB 192.00MiB 341.00MiB      59 188.41GiB  45.00
    1       5   Metadata/DUP    341.00MiB 192.00MiB 533.00MiB      60 188.41GiB  45.00
    1       6       Data/single 533.00MiB   1.00GiB   1.52GiB      49 169.91GiB  72.23
    1       7       Data/single   1.52GiB  16.00MiB   1.54GiB      69 191.68GiB  79.83
    1       8       Data/single   1.54GiB   1.00GiB   2.54GiB      17 100.90GiB  46.39
    1       9       Data/single   2.54GiB   1.00GiB   3.54GiB      16  99.90GiB  40.68
    1      10       Data/single   3.54GiB   1.00GiB   4.54GiB       1  71.40GiB  62.97
    1      11       Data/single   4.54GiB   1.00GiB   5.54GiB      33 125.04GiB  26.00
    1      12       Data/single   5.54GiB   1.00GiB   6.54GiB      50 170.91GiB  60.44
    1      13       Data/single   6.54GiB 512.00MiB   7.04GiB      63 189.16GiB  67.34
    1      14       Data/single   7.04GiB   1.00GiB   8.04GiB      51 171.91GiB  70.94


  • Devid -- the device id
  • PNumber -- the number of the chunk on the device (in order)
  • Type/profile -- the chunk type and profile
  • PStart -- the chunk start on the device
  • Length -- the chunk length (same for physical and logical address space)
  • PEnd -- the chunk end, effectively PStart + Length
  • LNumber -- the number of the chunk, in the logical address space of the whole filesystem
  • LStart -- the chunk start in the logical address space of the whole filesystem, as it's a single space it's also called offset
  • Usage -- chunk usage, percentage of used data/metadata of the chunk length

The chunks in the output can be sorted by one or more sorting criteria, evaluated as specified, in the ascending order. By default the chunks are sorted by devid and pstart, this is most convenient for single device filesystems.

On multi-device filesystems it's up to the user what is preferred as the layout of chunks on e.g. striped profiles (RAID0 etc) cannot be easily represented. A logical view with corresponding underlying structure would be better, but sorting by lstart,devid at least groups devices of the given logical range. Can be also combined with usage.

This output can provide information for balance filters.

Options

sort by a column (ascending):

MODE is a coma separated list of:

devid - by device id (default, with pstart)

pstart - physical start (relative to the beginning of the device)

lstart - logical offset (in the logical address space)

usage - by chunk usage (percentage)

length - by chunk length



raw numbers in bytes, without the B suffix
print human friendly numbers, base 1024, this is the default
select the 1024 base for the following options, according to the IEC standard
select the 1000 base for the following options, according to the SI standard
show sizes in KiB, or kB with --si
show sizes in MiB, or MB with --si
show sizes in GiB, or GB with --si
show sizes in TiB, or TB with --si


(needs root privileges)

Find device-specific physical offset of file that can be used for hibernation. Also verify that the file is suitable as a swapfile. See also command btrfs filesystem mkswapfile and the Swapfile feature description.

NOTE:

Do not use filefrag or FIEMAP ioctl values reported as physical, this is different due to internal filesystem mappings. The hibernation expects offset relative to the physical block device.


Options

print only the value suitable as resume offset for file /sys/power/resume_offset

(needs root privileges)

return the minimum size the device can be shrunk to, without performing any resize operation, this may be useful before executing the actual resize operation

Options

specify the device id to query, default is 1 if this option is not used


for a given file or directory, return the containing tree root id, but for a subvolume itself return its own tree id (i.e. subvol id)

NOTE:

The result is undefined for the so-called empty subvolumes (identified by inode number 2), but such a subvolume does not contain any files anyway


(needs root privileges)

resolve the absolute path of the subvolume id subvolid

(needs root privileges)

Print sizes and statistics of trees. This takes a device as an argument and not a mount point unlike other commands.

NOTE:

In case the the filesystem is still mounted it's possible to run the command but the results may be inaccurate or various errors may be printed in case there are ongoing writes to the filesystem. A warning is printed in such case.


Options

raw numbers in bytes, without the B suffix

Print stats only for the given treeid.
print human friendly numbers, base 1024, this is the default
select the 1024 base for the following options, according to the IEC standard
select the 1000 base for the following options, according to the SI standard
show sizes in KiB, or kB with --si
show sizes in MiB, or MB with --si
show sizes in GiB, or GB with --si
show sizes in TiB, or TB with --si


btrfs inspect-internal returns a zero exit status if it succeeds. Non zero is returned in case of failure.

btrfs is part of btrfs-progs. Please refer to the documentation at https://btrfs.readthedocs.io.

mkfs.btrfs(8)

January 7, 2025 6.12