sbin/fsdb/fsdb.8

         Copyright (c) 1988 Regents of the University of California.
 All rights reserved.

 This code is derived from software contributed to Berkeley by
 Computer Consoles Inc.

 Redistribution and use in source and binary forms are permitted
 provided that the above copyright notice and this paragraph are
 duplicated in all such forms and that any documentation,
 advertising materials, and other materials related to such
 distribution and use acknowledge that the software was developed
 by the University of California, Berkeley. The name of the
 University may not be used to endorse or promote products derived
 from this software without specific prior written permission.
 THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.

 @(#)fsdb.8 6.2 (Berkeley) 07/09/88

 FSDB 8 ""
C 7  NAME
fsdb - file system debugger
 SYNOPSIS
 /etc/fsdb  [ options ] special
 OPTIONS
The options available to
 fsdb\^ are:

 0
 13
 -? display usage
 13
 -o override some error conditions
 13
 "-p'string'\^" set prompt to string
 13
 -w open for write


 DESCRIPTION
Since
 fsdb reads the disk raw,
it is able to circumvent normal
file system security.
Extreme caution is advised
in determining its availability
on the system.
Suggested permissions are 600
and owned by bin.

 Fsdb\^ can be used
to patch up
a damaged file system
after a crash.
It has conversions
to translate block and i-numbers
into their corresponding disk addresses.
Also included are mnemonic offsets
to access different parts
of an inode.
These 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 the use of the
 o command.

 Fsdb\^ reads a block at a time
and will therefore work with raw as well as block
I/O.
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.
Note that in order to modify
any portion of the disk,
 fsdb must be invoked with the
 -w option.

Wherever possible,
 adb- like syntax was adopted
to promote the use
of
 fsdb through familiarity.

Numbers are considered hexadecimal by default.
However, the user has control over how data is
to be displayed
or accepted.
The
 base command will display
or set the input/output base.
Once set,
all input will default to this base
and all output will be shown in this base.
The base can be overriden temporarily for input by
preceding hexadecimal numbers with '0x', preceding
decimal numbers with '0t', or
octal numbers with '0'.
Hexadecimal numbers beginning with a-f or A-F must
be preceded with '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, superblock etc. to a
byte address.
Once the address has been calculated,
 fsdb will record the result in
 dot (see next paragraph).

Several global values are maintained by
 fsdb : the current base (referred to as
 base ), the current address (referred to as
 dot ), the current inode (referred to as
 inode ), the current count (referred to as
 count ), and the current type (referred to as
 type ). Most commands use the preset value of
 dot in
their execution.
For example,

 0
 7.2n
> 2:inode


will first set the value of
 dot to 2, ':' will alert the start of a command,
and the
 inode command will set
 inode to 2.
A count is specified after a ','.
Once set,
 count will remain at this value
until a new command is encountered
which will then reset the value back to 1 (the default).
So, if

 0
 7.2n
> 2000,400/X


is typed,
400 hex longs are listed
from 2000,
and when completed,
the value of
 dot will be 2000 + 400 * sizeof (long).
If a carriage-return is then typed,
the output routine will use the
current values of
 dot ,  count , and
 type and display 400 more hex longs.
A '*' will cause the entire block to
be displayed.

End of fragment, block and file are maintained by
 fsdb. When displaying data as fragments or blocks,
an error message will be displayed when the end of fragment
or block is reached.
When displaying data using the
 db,  ib,  directory, or
 file commands an error message is displayed if the
end of file is reached.
This is mainly needed
to avoid passing the
end of a directory or file
and getting unknown and unwanted results.

An example showing several commands and
the use of carriage-return would be:

 0
 7.2n
> 2:ino; 0:dir?d

or


 0
 7.2n
> 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,
subsequent carriage-returns (or +, -) will advance to subsequent
entries.
Note that

 0
 7.2n
> 2:inode; :ls

or


 0
 7.2n
> :ls /


is again synonymous.
 EXPRESSIONS

The symbols recognized by
 fsdb\^ are:
 7.2n
 carriage-return update the value of
 dot by the current value of
 type and display using the current value of
 count .  7.2n
 # numeric expressions may be composed of +, -, *, and % operators
(evaluated left to right) and may use parentheses. Once evaluated,
the value of
 dot is updated.
 7.2n
 , " count"\^ count indicator. The global value of
 count will be updated to
 count . The value of
 count will remain until a new command is run.
A count specifier of '*' will attempt to show a
 blocks's worth of information.
The default for
 count is 1.
 7.2n
 ? " f\^" display in structured style with format
specifier
 f (see FORMATTED OUTPUT section).
 7.2n
 / " f\^" display in unstructured style with format
specifier
 f (see FORMATTED OUTPUT section).
 7.2n
 . the value of
 dot .  7.2n
 + "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.
 7.2n
 - "e\^" decrement the value of
 dot by the expression
 e (see +).
 7.2n
 * "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.
 7.2n
 % "e\^" divide the value of
 dot by the expression
 e (see *).
 7.2n
 < " name\^" restore an address saved in register
 name .  name must be a single letter or digit.
 7.2n
 > " name\^" save an address in register
 name .  name must be a single letter or digit.
 7.2n
 = " f" display indicator.
If
 f is a legitimate format specifier
(see FORMATTED OUTPUT
section),
then the value of
 dot is displayed using
format specifier
 f . Otherwise,
assignment is assumed
(see next item).
 7.2n
 = " [s] [e]\^" 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 may be useful for changing
directory names or
 ASCII file information.
 7.2n
 =+ " e\^" incremental assignment.
The address pointed to by
 dot has its contents incremented by expression
 e .  7.2n
 =- " e\^" decremental assignment.
The address pointed to by
 dot has its contents decremented by expression
 e .  COMMANDS

A command must be prefixed by a ':' character.
Only enough letters of the command
to uniquely
distinguish it are needed.
Multiple commands may be entered
on one line by separating
them by a space, tab or ';'.

In order to view a potentially
unmounted disk in a reasonable
manner,
 fsdb\^ offers the
 cd ,  pwd ,  ls and
 find commands.
The functionality of these
commands substantially matches those of
its
 UNIX counterparts
(see individual command for details).
The '*', '?', and '[-]' wild card
characters are available.
 7.2n
 base=b display or set base. As stated above,
all input and output is governed by
the current
 base . If the '=b' is left off,
the current
 base is displayed.
Otherwise, the current
 base is set
to
 b. Note that this 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.
 7.2n
 block convert the value of
 dot to a block address.
 7.2n
 cd dir change the current directory
to directory
 dir. The current values of
 inode and
 dot are also updated.
If no
 dir is specified,
then change directories to
inode 2 ("/").
 7.2n
 cg convert the value of
 dot to a cylinder group.
 7.2n
 directory If the current
 inode is a directory,
then the value of
 dot is converted to a directory
slot offset in that directory
and
 dot now points to
this entry.
 7.2n
 file the value of
 dot is taken as
a relative block count from the
beginning of the file.
The value of
 dot is updated to the first byte
of this block.
  7.2n
 find " dir [-name n] [-inum i]\^" find files by name or i-number.
 find recursively searches
directory
 dir and below for filenames whose
i-number matches
 i or whose name
matches pattern
 n . Note that only one of the two options
(-name or -inum)
may be used at one time.
Also, the -print is not needed or
accepted.
 7.2n
 fill "=p\^" fill an area of disk with pattern
 p. The area of disk
is delimited by
 dot and
 count .  7.2n
 fragment convert the value of
 dot to
a fragment address.
The only difference between the
 fragment command and the
 block command is the amount that
is able to be displayed.
 7.2n
 inode convert the value of
 dot to an inode address.
If successful,
the current value of
 inode will be 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.
 7.2n
 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 may be used (but, if used,
 must be specified before the
filename specifiers).
Also, as stated above,
wild card characters are
available and multiple
arguments may be given.
The long listing shows only
the i-number and the name;
use the
 inode command with '?i'
to get more information.
 7.2n
 override toggle the value of override.
Some error conditions may be
overriden
if override is toggled on.
 7.2n
 prompt " p\^" change the fsdb prompt to
 p.  p must be surrounded by (")s.
 7.2n
 pwd display the current working directory.
 7.2n
 quit quit
 fsdb .  7.2n
 sb the value of
 dot is taken as a cylinder group
number and then converted to
the address of the superblock
in that cylinder group.
As a shorthand, ':sb' at
the beginning of a line
will set the value of
 dot to
 the superblock and display it
in superblock format.
 7.2n
 ! escape to shell
 INODE COMMANDS
In addition to the above commands,
there are several commands that deal with inode
fields and operate directly on the current
 inode (they still require the ':').
They may 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 to point to
that particular field.
For example,

 0
 7.2n
> :ln=+1


would
increment the link count of the current
 inode and set the value of
 dot to the address of the link
count field.
 7.2n
 at access time.
 7.2n
 bs block size.
 7.2n
 ct creation time.
 7.2n
 db use the current value of
 dot as a direct block index,
where direct blocks number from
0 - 11.
In order to display the block
itself, you need to 'pipe' this
result into the
 block or
 fragment command.
For example,

 > 1:db:block,20/X

would get the contents of
data block field 1 from the inode and
convert it to a block address.
20 longs are then displayed in hexadecimal
(see FORMATTED OUTPUT section).
 7.2n
 gid group id.
 7.2n
 ib use the current value of
 dot as an indirect block index
where indirect blocks number from
0 - 2.
This will only get the indirect block itself
(the block containing the pointers to the actual blocks).
Use the
 file command and start at block 12 to get to the actual
blocks.
 7.2n
 ln link count.
 7.2n
 mt modification time.
 7.2n
 md mode.
 7.2n
 maj major device number.
 7.2n
 min minor device number.
 7.2n
 nm although listed here,
this command actually
operates on the directory
name field.
Once poised at the desired
directory entry (using the
 directory command),
this command will allow
you to change or display
the directory name.
For example,

 > 7:dir:nm="foo"

will get the 7th directory
entry of the current
 inode and change its name to foo.
Note that names
cannot be made larger than the
field is set up for.
If an attempt is made,
the string is truncated to fit
and a warning message to this
effect is displayed.
 7.2n
 sz file size.
 7.2n
 uid user id.
 FORMATTED OUTPUT

There are two styles
and many format types.
The two styles are structured and
unstructured.
Structured output is used to display
inodes, directories, superblocks and the
like.
Unstructured just displays
raw data.
The following table shows the
different ways of displaying:
 7.2n
 ?
 0
 13
 c display as cylinder groups
 13
 i display as inodes
 13
 d display as directories
 13
 s display as superblocks


 7.2n
 /
 0
 13
 b display as bytes
 13
 c display as characters
 13
 o O display as octal shorts or longs
 13
 d D display as decimal shorts or longs
 13
 x X display as hexadecimal shorts or longs


The format specifier immediately follows
the '/' or '?' character.
The values displayed by '/b' and all '?'
formats are displayed in the current
 base . Also,
 type is appropriately updated
upon completion.
 EXAMPLES
 16
> 2000+400%(20+20)=D
will display 2010 in decimal (use of
 fsdb as a calculator
for complex arithmetic).
 16
> 386:ino?i
display i-number 386 in an inode format.
This now becomes the current
 inode .  16
> :ln=4
changes the link count for the
current
 inode to 4.
 16
> :ln=+1
increments the link count by 1.
 16
> :ct=X
display the creation time as a hexadecimal long.
 16
> :mt=t
display the modification time in time format.
 16
> 0:file/c
displays, in
 ASCII , block zero of the file associated
with the
current
 inode .  16
> 2:ino,*?d
displays the first blocks worth of directory entries for
the root inode of this file system.
It will stop prematurely if the eof is reached.
 16
> 5:dir:inode; 0:file,*/c
changes the current inode to that
associated with the 5th directory entry
(numbered from zero)
of the current
 inode. The first logical block of the file
is then displayed in
 ASCII .  16
> :sb
displays the superblock of this file system.
 16
> 1:cg?c
displays cylinder group information and summary
for cylinder group 1.
 16
> 2:inode; 7:dir=3
changes the i-number for the
seventh directory slot in the root directory to 3.
 16
> 7:dir:nm="name"
changes the name field
in the directory slot to
 name .  16
> 2:db:block,*?d
displays the third block of the current
 inode as directory entries.
 16
> 3c3:fragment,20:fill=0x20
get fragment 3c3 and fill 20
 type elements
with 0x20.
 16
> 2050=0xffff
set the contents of address 2050 to 0xffffffff.
0xffffffff may be truncated depending on the current
 type.  16
> 1c92434="this is some text"
will place the
 ASCII for the string at
1c92434.
 SEE ALSO
fsck(8), dir(4), fs(5).
 BUGS

Extreme caution is advised in
determining the availability
of
 fsdb on the system.
Suggested permissions are 600 and
owned by bin.