Tribblix: manual page: fsdb

FSDB_UDFS(8) Maintenance Commands and Procedures FSDB_UDFS(8)

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:

o Current base (referred to as base)

o Current address (referred to as dot)

o Current inode (referred to as inode)

o Current count (referred to as count)

o 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"