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.
- dump-super [options]
<device> [device...]
- 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...]
- 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, i.e. the root tree keys
- -R|--backups
- same as --roots plus print backup root info, i.e. 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
<block_num>
- --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, 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
- inode-resolve [-v]
<ino> <path>
- (needs root privileges)
resolve paths to all files with given inode number ino
in a given subvolume at path, i.e. 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 64KiB, maximum 16MiB. Buffer sizes over 64Kib require kernel support
for the V2 ioctl (added in 4.15).
- -v
- (deprecated) alias for global -v option
- map-swapfile [options]
<file>
- (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
- -r|--resume-offset
- print only the value suitable as resume offset for file
/sys/power/resume_offset
- 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 (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
- 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. 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
- -b
- Print raw numbers in bytes.
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.