FSDB(8) FreeBSD System Manager's Manual FSDB(8)


fsdbFFS debugging/editing tool


fsdb [ -d][ -f][ -r] fsname


The fsdb utility opens fsname (usually a raw disk partition) and runs a command loop allowing manipulation of the file system's inode data. You are prompted to enter a command with fsdb (inum X)> where X is the currently selected i-number. The initial selected inode is the root of the file system (i-number 2). The command processor uses the editline(3) library, so you can use command line editing to reduce typing if desired. When you exit the command loop, the file system superblock is marked dirty and any buffered blocks are written to the file system.

The following options are available:

Enable additional debugging output (which comes primarily from fsck(8)-derived code).
Left for historical reasons and has no meaning.
Open the file system read/only, and disables all commands that would write to it.


Besides the built-in editline(3) commands, fsdb supports these commands:

Print out the list of accepted commands.

inode i-number
Select inode i-number as the new current inode.

Revert to the previously current inode.

clri i-number
Clear i-number.

lookup name
cd name
Find name in the current directory and make its inode the current inode. Name may be a multi-component name or may begin with slash to indicate that the root inode should be used to start the lookup. If some component along the pathname is not found, the last valid directory encountered is left as the active inode. This command is valid only if the starting inode is a directory.

Print out the active inode.

Print out the block list of the active inode. Note that the printout can become long for large files, since all indirect block pointers will also be printed.

findblk disk_block_number ...
Find the inode(s) owning the specified disk block(s) number(s). Note that these are not absolute disk blocks numbers, but offsets from the start of the partition.

Increment the active inode's link count.

Decrement the active inode's link count.

linkcount number
Set the active inode's link count to number.

List the current inode's directory entries. This command is valid only if the current inode is a directory.

rm name
del name
Remove the entry name from the current directory inode. This command is valid only if the current inode is a directory.

ln ino name
Create a link to inode ino under the name name in the current directory inode. This command is valid only if the current inode is a directory.

chinum dirslot inum
Change the i-number in directory entry dirslot to inum.

chname dirslot name
Change the name in directory entry dirslot to name. This command cannot expand a directory entry. You can only rename an entry if the name will fit into the existing directory slot.

chtype type
Change the type of the current inode to type. Type may be one of: file, dir, socket, or fifo.

chmod mode
Change the mode bits of the current inode to mode. You cannot change the file type with this subcommand; use chtype to do that.

chflags flags
Change the file flags of the current inode to flags.

chown uid
Change the owner of the current inode to uid.

chgrp gid
Change the group of the current inode to gid.

chgen gen
Change the generation number of the current inode to gen.

btime time
mtime time
ctime time
atime time
Change the creation (birth), modification, change, or access time (respectively) on the current inode to time. Time should be in the format YYYYMMDDHHMMSS[.nsec] where nsec is an optional nanosecond specification. If no nanoseconds are specified, the birthnsec, mtimensec, ctimensec, or atimensec field will be set to zero. Note that btime is available on UFS2 file systems only.

quit, q, exit, <EOF>
Exit the program.


The fsdb utility uses the source code for fsck(8) to implement most of the file system manipulation code. The remainder of fsdb first appeared in NetBSD, written by John T. Kohl.

Peter Wemm ported it to FreeBSD.


Manipulation of ``short'' symlinks has no effect. In particular, one should not try changing a symlink's type.

You must specify modes as numbers rather than symbolic names.

There are a bunch of other things that you might want to do which fsdb does not implement.


Use this tool with extreme caution--you can damage an FFS file system beyond what fsck(8) can repair.
August 24, 2006 FreeBSD