Revision as of 17:11, 19 October 2021

btrfs-inspect-internal(8) manual page

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

dump-super [options] <device> [device…]

(replaces the standalone tool btrfs-show-super)

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

-f|--full

print full superblock information, including the system chunk array and backup roots

-a|--all

print information about all present superblock copies (cannot be used together with -s option)

-i <super>

(deprecated since 4.8, same behaviour as --super)

--bytenr <bytenr>

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.

-F|--force

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

-s|--super <bytenr>

(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 [options] <device> [device…]

(replaces the standalone tool btrfs-debug-tree)

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

-e|--extents

print only extent-related information: extent and device trees

-d|--device

print only device-related information: tree root, chunk and device trees

-r|--roots

print only short root node information, ie. the root tree keys

-R|--backups

same as --roots plus print backup root info, ie. the backup root keys and the respective tree root block offset

-u|--uuid

print only the uuid tree information, empty output if the tree does not exist

-b <block_num>

print info of the specified block only, can be specified multiple times

--follow

use with -b, print all children tree blocks of <em><block_num></em>

--dfs

(default up to 5.2)

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

--bfs

(default since 5.3)

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

--hide-names

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.

--csum-headers

print b-tree node checksums stored in headers (metadata)

--csum-items

print checksums stored in checksum items (data)

--noscan

do not automatically scan the system for other devices from the same filesystem, only use the devices provided as the arguments

-t <tree_id>

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, eg. BTRFS_ROOT_TREE_OBJECTID

• short forms without BTRFS_ prefix, without _TREE and _OBJECTID suffix, eg. ROOT_TREE, ROOT

• convenience aliases, eg. DEVICE for the DEV tree, CHECKSUM for CSUM

• unrecognized ID is an error

inode-resolve [-v] <ino> <path>

(needs root privileges)

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

Options

-v

(deprecated) alias for global -v option

logical-resolve [-Pvo] [-s <bufsize>] <logical> <path>

(needs root privileges)

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

Options

-P

skip the path resolving and print the inodes instead

-o

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.

-s <bufsize>

set internal buffer for storing the file names to bufsize, default is 64k, maximum 16m. Buffer sizes over 64K require kernel support for the V2 ioctl (added in 4.15).

-v

(deprecated) alias for global -v option

min-dev-size [options] <path>

(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

--id <id>

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

rootid <path>

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

subvolid-resolve <subvolid> <path>

(needs root privileges)

resolve the absolute path of the subvolume id subvolid

tree-stats [options] <device>

(needs root privileges)

Print sizes and statistics of trees.

Options

-b

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 btrfs wiki http://btrfs.wiki.kernel.org for further details.

SEE ALSO

mkfs.btrfs(8)