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.Dd May 29, 2021
.Dt FSDB 8
.Os
.Sh NAME
.Nm fsdb
.Nd FFS debugging/editing tool
.Sh SYNOPSIS
.Nm
.Op Fl dFnN
.Fl f Ar fsname
.Sh DESCRIPTION
.Nm
opens
.Ar 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
.Dq "fsdb (inum X)>"
where
.Va X
is the currently selected i-number.
The initial selected inode is the root of the filesystem (i-number 2).
The command processor uses the
.Xr 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.
.Pp
The
.Fl d
option enables additional debugging output (which comes primarily from
.Xr fsck 8 Ns -derived
code).
.Pp
The
.Fl F
option indicates that
.Ar filesystem
is a file system image, rather than a raw character device.
It will be accessed
.Sq as-is ,
and no attempts will be made to read a disklabel.
.Pp
The
.Fl n
option disables writing to the device, preventing any changes from being made
to the filesystem.
.Pp
The
.Fl N
option causes the superblock not to be marked dirty when
.Nm
exits.
.Sh COMMANDS
Besides the built-in
.Xr editline 3
commands,
.Nm
supports these commands:
.Pp
.Bl -tag -width indent -compact
.It Cm help
Print out the list of accepted commands.
.Pp
.It Cm inode Ar i-number
Select inode
.Ar i-number
as the new current inode.
.Pp
.It Cm back
Revert to the previously current inode.
.Pp
.It Cm clri Ar i-number
Clear the inode
.Ar i-number .
.Pp
.It Cm lookup Ar name
.It Cm cd Ar name
Find
.Ar name
in the current directory and make its inode the current inode.
.Ar 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.
.br
This command is valid only if the starting inode is a directory.
.Pp
.It Cm active
.It Cm print
Print out the active inode.
.Pp
.It Cm uplink
Increment the active inode's link count.
.Pp
.It Cm downlink
Decrement the active inode's link count.
.Pp
.It Cm linkcount Ar number
Set the active inode's link count to
.Ar number .
.Pp
.It Cm ls
List the current inode's directory entries.
This command is valid only if the current inode is a directory.
.Pp
.It Cm blks
List the current inode's blocks numbers.
.Pp
.It Cm findblk Ar 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.
.Pp
.It Cm saveblks Ar filename
Save the current inode's data into
.Ar filename .
.Pp
.It Cm rm Ar name
.It Cm del Ar name
Remove the entry
.Ar name
from the current directory inode.
This command is valid only if the current inode is a directory.
.Pp
.It Cm ln Ar ino Ar name
Create a link to inode
.Ar ino
under the name
.Ar name
in the current directory inode.
This command is valid only if the current inode is a directory.
.Pp
.It Cm chinum Ar dirslot Ar inum
Change the i-number in directory entry
.Ar dirslot
to
.Ar inum .
.Pp
.It Cm chname Ar dirslot Ar name
Change the name in directory entry
.Ar dirslot
to
.Ar name .
This command cannot expand a directory entry.
You can only rename an entry if the name will fit into
the existing directory slot.
.Pp
.It Cm chtype Ar type
Change the type of the current inode to
.Ar type .
.Ar type
may be one of:
.Em file ,
.Em dir ,
.Em socket ,
or
.Em fifo .
.Pp
.It Cm chmod Ar mode
Change the mode bits of the current inode to
.Ar mode .
You cannot change the file type with this subcommand; use
.Ic chtype
to do that.
.Pp
.It Cm chflags Ar flags
Change the file flags of the current inode to
.Ar flags .
.Pp
.It Cm chown Ar uid
Change the owner of the current inode to
.Ar uid .
.Pp
.It Cm chgrp Ar gid
Change the group of the current inode to
.Ar gid .
.Pp
.It Cm chgen Ar gen
Change the generation number of the current inode to
.Ar gen .
.Pp
.It Cm mtime Ar time
.It Cm ctime Ar time
.It Cm atime Ar time
.It Cm birthtime Ar time
Change the modification, change, access time, or birthtime (respectively) on the
current inode to
.Ar time .
.Ar Time
should be in the format
.Em YYYYMMDDHHMMSS[.nsec]
where
.Em nsec
is an optional nanosecond specification.
If no nanoseconds are specified, the
.Va mtimensec ,
.Va ctimensec ,
.Va atimensec ,
or
.Va birthtimensec
field will be set to zero.
The birthtime field is only available on ufs2 filesystems.
.Pp
.It Cm quit , Cm q , Cm exit , Aq Em EOF
Exit the program.
.El
.Sh SEE ALSO
.Xr editline 3 ,
.Xr fs 5 ,
.Xr clri 8 ,
.Xr fsck 8
.Sh HISTORY
.Nm
uses the source code for
.Xr fsck 8
to implement most of the file system manipulation code.
The remainder of
.Nm
first appeared in
.Nx 1.1 .
.Sh WARNING
Use this tool with extreme caution -- you can damage an FFS file system
beyond what
.Xr fsck 8
can repair.
.Sh BUGS
Manipulation of
.Dq short
symlinks doesn't work (in particular, don't
try changing a symlink's type).
.br
You must specify modes as numbers rather than symbolic names.
.br
There are a bunch of other things that you might want to do which
.Nm
doesn't implement.