4.3BSD-Reno/share/man/cat8/fsdb.0
FSDB(8) 1990 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 nor-
mal file system security. Extreme caution is advised in
determining its availability on the system. Suggested per-
missions 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 correcting 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 neces-
sary 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 por-
tion 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 hexade-
cimal numbers with '0x', preceding decimal numbers with
'0t', or octal numbers with '0'. Hexadecimal numbers begin-
ning with a-f or A-F must be preceded with '0x' to distin-
guish them from commands.
Printed 7/27/90 June 1
FSDB(8) 1990 FSDB(8)
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 encountered
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 com-
pleted, 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
carriage-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 subse-
quent entries. Note that
> 2:inode; :ls
or
> :ls /
is again synonymous.
EEXXPPRREESSSSIIOONNSS
Printed 7/27/90 June 2
FSDB(8) 1990 FSDB(8)
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 information.
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. Mul-
tiplication 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
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).
Printed 7/27/90 June 3
FSDB(8) 1990 FSDB(8)
== [_s] [_e]
assignment indicator. The address pointed to by _d_o_t
has its contents changed to the value of the expres-
sion _e or to the _A_S_C_I_I representation of the quoted
(") string _s. This may be useful for changing direc-
tory 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 commands.
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. Other-
wise, 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 hex-
adecimal.
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.
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.
Printed 7/27/90 June 4
FSDB(8) 1990 FSDB(8)
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 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.
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 convenient
shorthand, if ':inode' appears at the beginning 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 specified,
the current directory is assumed. Either or both of
the options may be used (but, if used, _m_u_s_t be speci-
fied 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 information.
oovveerrrriiddee
toggle the value of override. Some error conditions
may be overriden if override is toggled on.
pprroommpptt _p
change the fsdb prompt to _p. _p must be surrounded 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 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 _d_o_t to _t_h_e
superblock and display it in superblock format.
Printed 7/27/90 June 5
FSDB(8) 1990 FSDB(8)
!! 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' com-
mands. 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 command. For exam-
ple,
> 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 OUT-
PUT 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 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 operates
on the directory name field. Once poised at the
Printed 7/27/90 June 6
FSDB(8) 1990 FSDB(8)
desired directory entry (using the _d_i_r_e_c_t_o_r_y com-
mand), 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 displayed.
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 following 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
The format specifier immediately follows the '/' or '?'
character. The values displayed by '/b' and all '?' formats
are displayed in the current _b_a_s_e. Also, _t_y_p_e is appropri-
ately 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.
Printed 7/27/90 June 7
FSDB(8) 1990 FSDB(8)
> :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 directory
entries for the root inode of this file sys-
tem. It will stop prematurely if the eof is
reached.
> 5:dir:inode; 0:file,*/c
changes the current inode to that associated
with the 5th directory entry (numbered from
zero) of the current _i_n_o_d_e. The first logi-
cal block of the file is then displayed in
_A_S_C_I_I.
> :sb displays the superblock of this file system.
> 1:cg?c displays cylinder group information and sum-
mary for cylinder group 1.
> 2:inode; 7:dir=3
changes the i-number for the seventh direc-
tory slot in the root directory to 3.
> 7:dir:nm="name"
changes the name field in the directory 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(4).
Printed 7/27/90 June 8
FSDB(8) 1990 FSDB(8)
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.
Printed 7/27/90 June 9