Manual Pages  — FSDB

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:

-d
	Enable additional debugging output (which comes primarily from fsck(8)-derived code).
-f
	Left for historical reasons and has no meaning.
-r
	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:

help	Print out the list of accepted commands.
inode i-number
	Select inode i-number as the new current inode.
back	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.
active print
	Print out the active inode.
blocks
	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.
uplink
	Increment the active inode's link count.
downlink
	Decrement the active inode's link count.
linkcount number
	Set the active inode's link count to number.
ls	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.

editline(3), fs(5), clri(8), fsck(8)

The fsdb utility appeared in BSD 4.3 Tahoe . It used the source code for fsck(8) to implement most of the file system manipulation code. The remainder of fsdb appeared in NetBSD written by John T. Kohl. It first appeared in FreeBSD 2.1.5 ported by Peter Wemm.

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