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

NAME

btrfs-inspect-internal - query various internal information

SYNOPSIS

btrfs inspect-internal <subcommand> <args>

DESCRIPTION

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.

SUBCOMMAND

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:

Contains file names, consider that if you're asked to send the dump for analysis. Does not contain file data.


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)

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

Print raw numbers in bytes.


EXIT STATUS

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

AVAILABILITY

btrfs is part of btrfs-progs. Please refer to the documentation at https://btrfs.readthedocs.io or wiki http://btrfs.wiki.kernel.org for further information.

SEE ALSO

mkfs.btrfs(8)

April 30, 2023 6.2