xfs_bmap (8) - Linux Manuals

xfs_bmap: print block mapping for an XFS file

NAME

xfs_bmap - print block mapping for an XFS file

SYNOPSIS

xfs_bmap [ -adlpv ] [ -n num_extents ] file
xfs_bmap -V

DESCRIPTION

xfs_bmap prints the map of disk blocks used by files in an XFS filesystem. The map lists each extent used by the file, as well as regions in the file that do not have any corresponding blocks (holes). Each line of the listings takes the following form:

extent: [startoffset..endoffset]: startblock..endblock

Holes are marked by replacing the startblock..endblock with hole. All the file offsets and disk blocks are in units of 512-byte blocks, no matter what the filesystem's block size is.

OPTIONS

-a

If this option is specified, information about the file's attribute fork is printed instead of the default data fork.

-c

If this option is specified, information about the file's copy on write fork is printed instead of the default data fork.

-d

If portions of the file have been migrated offline by a DMAPI application, a DMAPI read event will be generated to bring those portions back online before the disk block map is printed. However if the -d option is used, no DMAPI read event will be generated for a DMAPI file and offline portions will be reported as holes.

-e

If this option is used, xfs_bmap obtains all delayed allocation extents, and does not flush dirty pages to disk before querying extent data. With the -v option, the flags column will show which extents have not yet been allocated.

-l

If this option is used, then

<nblocks> blocks

will be appended to each line. nblocks is the length of the extent described on the line in units of 512-byte blocks.

This flag has no effect if the -v option is used.

-n num_extents

If this option is given, xfs_bmap obtains the extent list of the file in groups of num_extents extents. In the absence of -n, xfs_bmap queries the system for the number of extents in the file and uses that value to compute the group size.

-p

If this option is used, xfs_bmap obtains all unwritten (preallocated) extents that do not contain written data. With the -v option, the flags column will show which extents are preallocated/unwritten.

-v

Shows verbose information. When this flag is specified, additional AG specific information is appended to each line in the following form:

agno (startagoffset..endagoffset) nblocks flags

A second -v option will print out the flags legend.

-V

Prints the version number and exits.