4.4BSD/usr/share/man/cat8/fsdb.0
FSDB(8) BSD System Manager's Manual FSDB(8)
NNAAMMEE
fsdb - file system debugger
SSYYNNOOPPSSIISS
ffssddbb [ooppttiioonnss] special
OOPPTTIIOONNSS
The options available to _f_s_d_b are:
--?? display usage
--oo override some error conditions
--pp''ssttrriinngg'' set prompt to string
--ww open for write
DDEESSCCRRIIPPTTIIOONN
Since _f_s_d_b 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.
_F_s_d_b 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 correct-
ing control block entries or descending the file system
tree.
_F_s_d_b contains several error-checking routines to verify
inode and block addresses. These can be disabled if nec-
essary by invoking _f_s_d_b with the _-_o option or by the use
of the _o command.
_F_s_d_b 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, _f_s_d_b must be invoked with the _-_w
option.
Wherever possible, _a_d_b_-like syntax was adopted to promote
the use of _f_s_d_b through familiarity.
Numbers are considered hexadecimal by default. However,
the user has control over how data is to be displayed or
accepted. The _b_a_s_e 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
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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 _f_s_d_b is at the byte level. However,
_f_s_d_b offers many commands to convert a desired inode,
directory entry, block, superblock etc. to a byte address.
Once the address has been calculated, _f_s_d_b will record the
result in _d_o_t (see next paragraph).
Several global values are maintained by _f_s_d_b: the current
base (referred to as _b_a_s_e), the current address (referred
to as _d_o_t), the current inode (referred to as _i_n_o_d_e), the
current count (referred to as _c_o_u_n_t), and the current type
(referred to as _t_y_p_e). Most commands use the preset value
of _d_o_t in their execution. For example,
> 2:inode
will first set the value of _d_o_t to 2, ':' will alert the
start of a command, and the _i_n_o_d_e command will set _i_n_o_d_e
to 2. A count is specified after a ','. Once set, _c_o_u_n_t
will remain at this value until a new command is encoun-
tered which will then reset the value back to 1 (the
default). So, if
> 2000,400/X
is typed, 400 hex longs are listed from 2000, and when
completed, the value of _d_o_t will be 2000 + 400 * sizeof
(long). If a carriage-return is then typed, the output
routine will use the current values of _d_o_t, _c_o_u_n_t, and
_t_y_p_e and display 400 more hex longs. A '*' will cause the
entire block to be displayed.
End of fragment, block and file are maintained by _f_s_d_b_.
When displaying data as fragments or blocks, an error mes-
sage will be displayed when the end of fragment or block
is reached. When displaying data using the _d_b_, _i_b_, _d_i_r_e_c_-
_t_o_r_y_, or _f_i_l_e 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 car-
riage-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, subsequent carriage-returns (or +, -) will advance
to subsequent entries. Note that
> 2:inode; :ls
or
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> :ls /
is again synonymous.
EEXXPPRREESSSSIIOONNSS
The symbols recognized by _f_s_d_b are:
ccaarrrriiaaggee--rreettuurrnn
update the value of _d_o_t by the current value of
_t_y_p_e and display using the current value of _c_o_u_n_t.
## numeric expressions may be composed of +, -, *, and
% operators (evaluated left to right) and may use
parentheses. Once evaluated, the value of _d_o_t is
updated.
,, _c_o_u_n_t
count indicator. The global value of _c_o_u_n_t will be
updated to _c_o_u_n_t. The value of _c_o_u_n_t will remain
until a new command is run. A count specifier of
'*' will attempt to show a _b_l_o_c_k_s_'_s worth of infor-
mation. The default for _c_o_u_n_t is 1.
?? _f display in structured style with format specifier _f
(see FORMATTED OUTPUT section).
// _f display in unstructured style with format specifier
_f (see FORMATTED OUTPUT section).
.. the value of _d_o_t.
++_e increment the value of _d_o_t by the expression _e_.
The amount actually incremented is dependent on the
size of _t_y_p_e:
dot = dot + e * sizeof (type)
The default for _e is 1.
--_e decrement the value of _d_o_t by the expression _e (see
+).
**_e multiply the value of _d_o_t by the expression _e_.
Multiplication and division don't use _t_y_p_e_. In the
above calculation of _d_o_t, consider the sizeof (
_t_y_p_e) to be 1.
%%_e divide the value of _d_o_t by the expression _e (see
*).
<< _n_a_m_e restore an address saved in register _n_a_m_e. _n_a_m_e
must be a single letter or digit.
>> _n_a_m_e save an address in register _n_a_m_e. _n_a_m_e must be a
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single letter or digit.
== _f display indicator. If _f is a legitimate format
specifier (see FORMATTED OUTPUT section), then the
value of _d_o_t is displayed using format specifier _f.
Otherwise, assignment is assumed (see next item).
== _[_s_] _[_e_]
assignment indicator. The address pointed to by
_d_o_t has its contents changed to the value of the
expression _e or to the _A_S_C_I_I representation of the
quoted (") string _s_. This may be useful for chang-
ing directory names or _A_S_C_I_I file information.
==++ _e incremental assignment. The address pointed to by
_d_o_t has its contents incremented by expression _e.
==-- _e decremental assignment. The address pointed to by
_d_o_t has its contents decremented by expression _e.
CCOOMMMMAANNDDSS
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 reason-
able manner, _f_s_d_b offers the _c_d, _p_w_d, _l_s and _f_i_n_d com-
mands. The functionality of these commands substantially
matches those of its _U_N_I_X counterparts (see individual
command for details). The '*', '?', and '[-]' wild card
characters are available.
bbaassee==bb display or set base. As stated above, all input
and output is governed by the current _b_a_s_e. If the
'=b' is left off, the current _b_a_s_e is displayed.
Otherwise, the current _b_a_s_e is set to _b_. Note that
this is interpreted using the old value of _b_a_s_e, so
to ensure correctness use the '0', '0t', or '0x'
prefix when changing the _b_a_s_e_. The default for
_b_a_s_e is hexadecimal.
bblloocckk convert the value of _d_o_t to a block address.
ccdd ddiirr change the current directory to directory _d_i_r_. The
current values of _i_n_o_d_e and _d_o_t are also updated.
If no _d_i_r is specified, then change directories to
inode 2 ("/").
ccgg convert the value of _d_o_t to a cylinder group.
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ddiirreeccttoorryy
If the current _i_n_o_d_e is a directory, then the value
of _d_o_t is converted to a directory slot offset in
that directory and _d_o_t now points to this entry.
ffiillee the value of _d_o_t is taken as a relative block count
from the beginning of the file. The value of _d_o_t
is updated to the first byte of this block.
ffiinndd _d_i_r _[_-_n_a_m_e _n_] _[_-_i_n_u_m _i_]
find files by name or i-number. _f_i_n_d recursively
searches directory _d_i_r and below for filenames
whose i-number matches _i or whose name matches pat-
tern _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.
ffiillll_=_p fill an area of disk with pattern _p_. The area of
disk is delimited by _d_o_t and _c_o_u_n_t.
ffrraaggmmeenntt
convert the value of _d_o_t to a fragment address.
The only difference between the _f_r_a_g_m_e_n_t command
and the _b_l_o_c_k command is the amount that is able to
be displayed.
iinnooddee convert the value of _d_o_t to an inode address. If
successful, the current value of _i_n_o_d_e will be
updated as well as the value of _d_o_t_. As a conve-
nient shorthand, if ':inode' appears at the begin-
ning of the line, the value of _d_o_t is set to the
current _i_n_o_d_e and that inode is displayed in inode
format.
llss _[_-_R_] _[_-_l_] _p_a_t_1 _p_a_t_2 _._._.
list directories or files. If no file is speci-
fied, the current directory is assumed. Either or
both of the options may be used (but, if used, _m_u_s_t
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 _i_n_o_d_e command with '?i' to get more infor-
mation.
oovveerrrriiddee
toggle the value of override. Some error condi-
tions may be overriden if override is toggled on.
pprroommpptt _p
change the fsdb prompt to _p_. _p must be surrounded
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by (")s.
ppwwdd display the current working directory.
qquuiitt quit _f_s_d_b.
ssbb the value of _d_o_t is taken as a cylinder group num-
ber 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 _d_o_t to _t_h_e superblock and display it in
superblock format.
!! escape to shell
IINNOODDEE CCOOMMMMAANNDDSS
In addition to the above commands, there are several com-
mands that deal with inode fields and operate directly on
the current _i_n_o_d_e (they still require the ':'). They may
be used to more easily display or change the particular
fields. The value of _d_o_t is only used by the ':db' and
':ib' commands. Upon completion of the command, the value
of _d_o_t is changed to point to that particular field. For
example,
> :ln=+1
would increment the link count of the current _i_n_o_d_e and
set the value of _d_o_t to the address of the link count
field.
aatt access time.
bbss block size.
cctt creation time.
ddbb use the current value of _d_o_t 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 _b_l_o_c_k or _f_r_a_g_m_e_n_t com-
mand. 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 FOR-
MATTED OUTPUT section).
ggiidd group id.
iibb use the current value of _d_o_t as an indirect block
index where indirect blocks number from 0 - 2.
This will only get the indirect block itself (the
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block containing the pointers to the actual
blocks). Use the _f_i_l_e command and start at block
12 to get to the actual blocks.
llnn link count.
mmtt modification time.
mmdd mode.
mmaajj major device number.
mmiinn minor device number.
nnmm although listed here, this command actually oper-
ates on the directory name field. Once poised at
the desired directory entry (using the _d_i_r_e_c_t_o_r_y
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
_i_n_o_d_e 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 dis-
played.
sszz file size.
uuiidd user id.
FFOORRMMAATTTTEEDD OOUUTTPPUUTT
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 fol-
lowing table shows the different ways of displaying:
??
cc display as cylinder groups
ii display as inodes
dd display as directories
ss display as superblocks
//
bb display as bytes
cc display as characters
oo OO display as octal shorts or longs
dd DD display as decimal shorts or longs
xx XX display as hexadecimal shorts or longs
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The format specifier immediately follows the '/' or '?'
character. The values displayed by '/b' and all '?' for-
mats are displayed in the current _b_a_s_e. Also, _t_y_p_e is
appropriately updated upon completion.
EEXXAAMMPPLLEESS
> 2000+400%(20+20)=D
will display 2010 in decimal (use of _f_s_d_b
as a calculator for complex arithmetic).
> 386:ino?i display i-number 386 in an inode format.
This now becomes the current _i_n_o_d_e.
> :ln=4 changes the link count for the current
_i_n_o_d_e to 4.
> :ln=+1 increments the link count by 1.
> :ct=X display the creation time as a hexadecimal
long.
> :mt=t display the modification time in time for-
mat.
> 0:file/c displays, in _A_S_C_I_I, block zero of the file
associated with the current _i_n_o_d_e.
> 2:ino,*?d displays the first blocks worth of direc-
tory entries for the root inode of this
file system. It will stop prematurely if
the eof is reached.
> 5:dir:inode; 0:file,*/c
changes the current inode to that associ-
ated with the 5th directory entry (num-
bered from zero) of the current _i_n_o_d_e_.
The first logical block of the file is
then displayed in _A_S_C_I_I.
> :sb displays the superblock of this file sys-
tem.
> 1:cg?c displays cylinder group information and
summary for cylinder group 1.
> 2:inode; 7:dir=3
changes the i-number for the seventh
directory slot in the root directory to 3.
> 7:dir:nm="name"
changes the name field in the directory
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slot to _n_a_m_e.
> 2:db:block,*?d
displays the third block of the current
_i_n_o_d_e as directory entries.
> 3c3:fragment,20:fill=0x20
get fragment 3c3 and fill 20 _t_y_p_e elements
with 0x20.
> 2050=0xffff set the contents of address 2050 to
0xffffffff. 0xffffffff may be truncated
depending on the current _t_y_p_e_.
> 1c92434="this is some text"
will place the _A_S_C_I_I for the string at
1c92434.
SSEEEE AALLSSOO
fsck(8), dir(4), fs(5).
BBUUGGSS
Extreme caution is advised in determining the availability
of _f_s_d_b on the system. Suggested permissions are 600 and
owned by bin.
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