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

fsdb — FFS debugging/editing tool

fsdb [-d] -f fsname

fsdb 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 options are as follows:

Enables additional debugging output (which comes primarily from fsck(8)-derived code).
fsname
Open file system fsname.

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

Print out the list of accepted commands.

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

Revert to the previously current inode.

i-number
Clear the inode i-number.

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
Print out the active inode.

Increment the active inode's link count.

Decrement the active inode's link count.

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.

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

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.

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

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.

type
Change the type of the current inode to type. type may be one of: , , , or .

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.

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

uid
Change the owner of the current inode to uid.

length
Change the length of the current inode to length.

gid
Change the group of the current inode to gid.

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

time, ctime time, atime time
Change the modification, change, or access time (respectively) on the current inode to time. Time should be in the format where is an optional nanosecond specification. If no nanoseconds are specified, the mtimensec, ctimensec, or atimensec field will be set to zero.

, q, exit,
Exit the program.

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

fsdb uses the source code for fsck(8) to implement most of the file system manipulation code. The remainder of fsdb first appeared in NetBSD 1.1.

Manipulation of “short” symlinks doesn't work (in particular, don't 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 doesn't implement.

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

April 23, 2020 OpenBSD-current