man/man8/fsdb_udfs.8

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 FSDB_UDFS 8 "August 29, 2021"
 NAME
fsdb_udfs - udfs file system debugger
 SYNOPSIS
fsdb  [-F] udfs [generic_option] [-o specific_option] special


 DESCRIPTION
The fsdb_udfs command is an interactive tool that can be used to patch up
a damaged udfs file system. fsdb_udfs has conversions to translate
block and i-numbers into their corresponding disk addresses. Mnemonic offsets
to access different parts of an inode are also included. Mnemonic offsets
greatly simplify the process of correcting control block entries or descending
the file system tree.

fsdb contains several error-checking routines to verify inode and block
addresses. These can be disabled if necessary by invoking fsdb with the
-o option or by using the o command.

fsdb reads one block at a time, and therefore works with raw as well as
block I/O devices. A buffer management routine is used to retain commonly
used blocks of data in order to reduce the number of read system calls. All
assignment operations result in an immediate write-through of the corresponding
block. In order to modify any portion of the disk, fsdb must be invoked
with the -w option.

Wherever possible, adb-like syntax has been adopted to promote the use of
fsdb through familiarity.
 OPTIONS
The following options are supported:
-o specific_option

Specify udfs file system specific options in a comma-separated list with
no intervening spaces. The following specific options are supported:
o

Override some error conditions.


p=string

Set prompt to string.


w

Open for write.


?

Display usage.


 USAGE
Numbers are considered hexadecimal by default. The user has control over how
data is to be displayed or accepted. The base command displays or sets
the input and output base. Once set, all input defaults to this base and all
output displays in this base. The base can be overridden temporarily for input
by preceding hexadecimal numbers by 0x, preceding decimal numbers with a
0t, or octal numbers with a 0. Hexadecimal numbers beginning with
a-f or A-F must be preceded with a 0x to
distinguish them from commands.

Disk addressing by fsdb is at the byte level. However, fsdb offers
many commands to convert a desired inode, directory entry, block, and so forth,
to a byte address. After the address has been calculated, fsdb records
the result in the current address (dot).

Several global values are maintained by fsdb:


Current base (referred to as base)


Current address (referred to as dot)


Current inode (referred to as inode)


Current count (referred to as count)


Current type (referred to as type)


Most commands use the preset value of dot in their execution. For
example,
 > 2:inode


first sets the value of dot (.) to 2, colon (:), signifies
the start of a command, and the inode command sets inode to
2. A count is specified after a comma (,). Once set, count remains
at this value until a new command is encountered that resets the value back to
1 (the default).

So, if
> 2000,400/X


is entered, 400 hex longs are listed from 2000, and when completed,
the value of dot is  2000 + 400 * sizeof (long). If a RETURN is then
entered, the output routine uses the current values of dot, count,
and type and displays 400 more hex longs. An asterisk (*)
causes the entire block to be displayed. An example showing several commands
and the use of RETURN would be:
> 2:ino; 0:dir?d


or
> 2:ino; 0:db:block?d


The two examples are synonymous for getting to the first directory entry of the
root of the file system. Once there, subsequently entering a RETURN, plus
(+), or minus (-) advances to subsequent entries. Notice that
> 2:inode; :ls


or
> :ls /


is again synonymous.
 "Expressions"
The following symbols are recognized by fsdb:
RETURN

Update the value of dot by the current value of type and display
using the current value of count.


#

Update the value of dot by specifying a numeric expression. Specify numeric
expressions using addition, subtraction, multiplication, and division
operators ( +, -, *, and %). Numeric expressions are
evaluated from left to right and can use parentheses. After evaluation, the
value of dot is updated.


, count

Update the count indicator. The global value of count is updated to
count. The value of count remains until a new command is run. A
count specifier of * attempts to show a blocks's worth of
information. The default for count is 1.


?  f

Display in structured style with format specifier f. See Formatted
Output.


/ f

Display in unstructured style with format specifier f. See Formatted
Output.


.

Display the value of dot.


+e

Increment the value of dot by the expression e. The amount actually
incremented is dependent on the size of type: dot = dot + e *
sizeof (type) The default for e is 1.


-e

Decrement the value of dot by the expression e . See +.


*e

Multiply the value of dot by the expression e. Multiplication and
division don't use type. In the above calculation of dot, consider the
sizeof (type) to be 1.


%e

Divide the value of dot by the expression e. See *.


< name

Restore an address saved in register name. name must be a single
letter or digit.


> name

Save an address in register name. name must be a single letter or
digit.


= f

Display indicator. If f is a legitimate format specifier (see
Formatted Output), then the value of dot is displayed using format
specifier f. Otherwise, assignment is assumed. See = [s] [e].


= [s] [e]

Change the value of dot using an assignment indicator. The address pointed to
by dot has its contents changed to the value of the expression e or to
the ASCII representation of the quoted (") string s. This can
be useful for changing directory names or ASCII file information.


=+ e

Change the value of dot using an incremental assignment. The address pointed to
by dot has its contents incremented by expression e.


=- e

Change the value of dot using a decremental assignment. Decrement the contents
of the address pointed to by dot by expression e.


 "Commands"
A command must be prefixed by a colon (:). Only enough letters of the
command to uniquely distinguish it are needed. Multiple commands can be entered
on one line by separating them by a SPACE, TAB, or semicolon (;).

To view a potentially unmounted disk in a reasonable manner, fsdb
supports the cd, pwd, ls, and find commands. The
functionality of each of these commands basically matches that of its UNIX
counterpart. See cd(1), pwd(1), ls(1), and find(1) for
details. The *, ,, ?, and - wildcard characters are
also supported.

The following commands are supported:
base[=b]

Display or set the base. All input and output is governed by the current base.
Without the = b, displays the current base. Otherwise, sets the
current base to b. Base is interpreted using the old value of base, so to
ensure correctness use the 0, 0t, or 0x prefix when changing
the base. The default for base is hexadecimal.


block

Convert the value of dot to a block address.


cd [dir]

Change the current directory to directory dir. The current values of
inode and dot are also updated. If dir is not specified, changes
directories to inode 2, root (/).


directory

If the current inode is a directory, converts the value of dot to a directory
slot offset in that directory, and dot now points to this entry.


file

Set the value of dot as a relative block count from the beginning of the file.
The value of dot is updated to the first byte of this block.


find dir [-name n] | [-inum i]

Find files by name or i-number. Recursively searches directory dir and
below for file names whose i-number matches i or whose name matches
pattern n. Only one of the two options (-name or -inum) can
be used at one time. The find -print is not necessary or accepted.


fill=p

Fill an area of disk with pattern p. The area of disk is delimited by dot
and count.


inode

Convert the value of dot to an inode address. If successful, the current value
of inode is updated as well as the value of dot. As a convenient shorthand, if
:inode appears at the beginning of the line, the value of dot is set to
the current inode and that inode is displayed in inode format.


ls [ -R ] [-l ] pat1 pat2...

List directories or files. If no file is specified, the current directory is
assumed. Either or both of the options can be used (but, if used, must be
specified before the filename specifiers). Wild card characters are available
and multiple arguments are acceptable. The long listing shows only the i-number
and the name; use the inode command with ?i to get more information.


override

Toggle the value of override. Some error conditions might be overridden if
override is toggled to on.


prompt "p"

Change the fsdb prompt to p. p must be enclosed in quotes.


pwd

Display the current working directory.


quit

Quit fsdb.


tag

Convert the value of dot and if this is a valid tag, print the volume structure
according to the tag.


!

Escape to the shell.


 "Inode Commands"
In addition to the above commands, several other commands deal with inode
fields and operate directly on the current inode (they still require the colon
(:). They can be used to more easily display or change the particular
fields. The value of dot is only used by the :db and :ib commands.
Upon completion of the command, the value of dot is changed so that it points
to that particular field. For example,
> :ln=+1


increments the link count of the current inode and sets the value of dot to the
address of the link count field.

The following inode commands are supported:
at

Access time


bs

Block size


ct

Creation time


gid

Group id


ln

Link number


mt

Modification time


md

Mode


maj

Major device number


min

Minor device number


nm

This command actually operates on the directory name field. Once poised at
the desired directory entry (using the directory command), this command
allows you to change or display the directory name. For example,
 > 7:dir:nm="foo"


gets the 7th directory entry of the current inode and changes its name to
foo. Directory names cannot be made larger than the field allows. If an
attempt is made to make a directory name larger than the field allows, the
string is truncated to fit and a warning message is displayed.


sz

File size


uid

User ID


uniq

Unique ID


 "Formatted Output"
Formatted output comes in two styles and many format types. The two styles of
formatted output are: structured and unstructured. Structured output is used to
display inodes, directories, and so forth. Unstructured output displays raw
data.

Format specifiers are preceded by the slash (/) or question mark
(?) character. type is updated as necessary upon completion.

The following format specifiers are preceded by the ? character:
i

Display as inodes in the current base.


d

Display as directories in the current base.


The following format specifiers are preceded by the / character:
b

Display as bytes in the current base.


c

Display as characters.


o | O

Display as octal shorts or longs.


d | D

Display as decimal shorts or longs.


x | X

Display as hexadecimal shorts or longs.


 EXAMPLES
Example 1 Using fsdb as a calculator for complex arithmetic

The following command displays 2010 in decimal format, and is an example
of using fsdb as a calculator for complex arithmetic.

> 2000+400%(20+20)=D


Example 2 Using fsdb to display an i-number in inode format

The following command displays the i-number 386 in inode format.386
becomes the current inode.

> 386:ino?i


Example 3 Using fsdb to change the link count

The following command changes the link count for the current inode to 4.

> :ln=4


Example 4 Using fsdb to increment the link count

The following command increments the link count by 1.

> :ln=+1


Example 5 Using fsdb to display the creation time as a hexadecimal long

The following command displays the creation time as a hexadecimal long.

> :ct=X


Example 6 Using fsdb to display the modification time in time format

The following command displays the modification time in time format.

> :mt=t


Example 7 Using fsdb to display in ASCII

The following command displays, in ASCII, block 0 of the file
associated with the current inode.

> 0:file/c


Example 8 Using fsdb to display the directory entries for the root inode

The following command displays the first block's directory entries for the root
inode of this file system. This command stops prematurely if the EOF is
reached.

> 2:ino,*?d


Example 9 Using fsdb to change the current inode

 The following command changes the current inode to that associated with the
5th directory entry (numbered from 0) of the current inode. The
first logical block of the file is then displayed in ASCII.

> 5:dir:inode; 0:file,*/c


Example 10 Using fsdb to change the i-number

 The following command changes the i-number for the 7th directory slot in
the root directory to 3.

> 2:inode; 7:dir=3


Example 11 Using fsdb to change the name field

The following command changes the name field in the directory slot to
name.

 > 7:dir:nm="name"


Example 12 Using fsdb to display the a block

The following command displays the 3rd block of the current inode as
directory entries.


Example 13 Using fsdb to set the contents of address

The following command sets the contents of address 2050 to
0xffffffff. 0xffffffff can be truncated, depending on the current
type.

> 2050=0xffff


Example 14 Using fsdb to place an ASCII string at an address

The following command places the ASCII string this is some text at
address 1c92434.

> 1c92434="this is some text"


 SEE ALSO
clri(8), fsck_udfs(8), dir(5), attributes(7)