FSDB_UFS(8) Maintenance Commands and Procedures FSDB_UFS(8)
NAME
fsdb_ufs - ufs file system debugger
SYNOPSIS
fsdb -F ufs [
generic_options] [
specific_options]
specialDESCRIPTION
The
fsdb_ufs command is an interactive tool that can be used to patch up
a damaged
UFS file system. 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 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. 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.
OPTIONS
The following option is supported:
-o Specify
UFS file system specific options. These options can be any
combination of the following separated by commas (with no
intervening spaces). The options available are:
? Display usage
o Override some error conditions
p='string' set prompt to string
w open for write
USAGE
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 overridden 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
and so forth to a byte address. Once the address has been calculated,
fsdb will record the result in dot (
.).
Several global values are maintained by
fsdb:
o the current base (referred to as
base),
o the current address (referred to as
dot),
o the current inode (referred to as
inode),
o the current count (referred to as
count),
o and the current type (referred to as
type).
Most commands use the preset value of
dot in their execution. For
example,
> 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
> 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
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
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, any subsequent
RETURN (or +,
-) will advance to subsequent entries. Note that
> 2:inode; :ls or
> :ls / is again synonymous.
Expressions
The symbols recognized by
fsdb are:
RETURN update the value of
dot by the current value of
type and
display using the current value of
count.
# numeric expressions may be composed of +, -, *, and %
operators (evaluated left to right) and may use parentheses.
Once evaluated, the value of
dot is updated.
, 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.
? f display in structured style with format specifier
f. See
Formatted Output.
/ f display in unstructured style with format specifier
f. See
Formatted Output.
. 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,
then the value of
dot is displayed using the format
specifier
f. See
Formatted Output. Otherwise, assignment is
assumed. See
=.
= [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.
=+ e incremental assignment. The address pointed to by
dot has
its contents incremented by expression
e.
=- 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 commands for details. The '*', '?', and '[-]' wild card
characters are available.
base=b display or set base. As stated above, all input and output is
governed by the current
base. If the
=b is omitted, 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.
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 no
dir is specified, then change
directories to inode
2 ("/").
cg convert the value of
dot to a cylinder group.
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.
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.
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.
fill=p fill an area of disk with pattern
p. The area of disk is delimited by
dot and
count.
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.
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.
log_chk run through the valid log entries without printing any information
and verify the layout.
log_delta count the number of deltas into the log, using the value of dot as an
offset into the log. No checking is done to make sure that offset is
within the head/tail offsets.
log_head display the header information about the file system logging. This
shows the block allocation for the log and the data structures on the
disk.
log_otodb return the physical disk block number, using the value of dot as an
offset into the log.
log_show display all deltas between the beginning of the log (BOL) and the
end of the log (EOL).
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.
override toggle the value of override. Some error conditions may be overridden
if override is toggled on.
prompt p change the
fsdb prompt to
p.
p must be surrounded by (")s.
pwd display the current working directory.
quit quit
fsdb.
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.
shadow if the current inode is a shadow inode, then the value of
dot is set
to the beginning of the shadow inode data.
! 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,
> :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.
at access time.
bs block size.
ct creation time.
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.
gid group id.
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.
ln link count.
mt modification time.
md mode.
maj major device number.
min minor device number.
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.
si shadow inode.
sz file size.
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 displays raw data.
The following shows the different ways of displaying:
? c display as cylinder groups
i display as inodes
d display as directories
s display as superblocks
S display as shadow inode data
/ b display as bytes
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
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
Example 1: Displaying in Decimal
The following command displays
2010 in decimal (use of
fsdb as a
calculator for complex arithmetic):
> 2000+400%(20+20)=D
Example 2: Displaying an i-number in Inode Format
The following command displays i-number
386 in an inode format. This now
becomes the current
inode:
> 386:ino?i
Example 3: Changing the Link Count
The following command changes the link count for the current
inode to
4:
> :ln=4
Example 4: Incrementing the Link Count
The following command increments the link count by
1:
> :ln=+1
Example 5: Displaying the Creation Time
The following command displays the creation time as a hexadecimal long:
> :ct=X
Example 6: Displaying the Modification Time
The following command displays the modification time in time format:
> :mt=t
Example 7: Displaying in ASCII
The following command displays in
ASCII, block zero of the file
associated with the current
inode:
> 0:file/c
Example 8: Displaying the First Block's Worth of Directorty Entries
The following command displays the first block's worth of directory
entries for the root inode of this file system. It will stop prematurely
if the
EOF is reached:
> 2:ino,*?d
Example 9: Displaying Changes to the Current Inode
The following command displays 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:
> 5:dir:inode; 0:file,*/c
Example 10: Displaying the Superblock
The following command displays the superblock of this file system:
> :sb
Example 11: Displaying the Cylinder Group
The following command displays cylinder group information and summary for
cylinder group
1:
> 1:cg?c
Example 12: Changing the i-number
The following command changes the i-number for the seventh directory slot
in the root directory to
3:
> 2:inode; 7:dir=3
Example 13: Displaying as Directory Entries
The following command displays the third block of the current
inode as
directory entries:
> 2:db:block,*?d
Example 14: Changing the Name Field
The following command changes the name field in the directory slot to
name:
> 7:dir:nm="name"
Example 15: Getting and Filling Elements
The following command gets fragment
3c3 and fill
20 type elements with
0x20:
> 3c3:fragment,20:fill=0x20
Example 16: Setting the Contents of an Address
The following command sets the contents of address
2050 to
0xffffffff.
0xffffffff may be truncated depending on the current
type:
> 2050=0xffff
Example 17: Placing ASCII
The following command places the
ASCII for the string at
1c92434:
> 1c92434="this is some text"
Example 18: Displaying Shadow Inode Data
The following command displays all of the shadow inode data in the shadow
inode associated with the root inode of this file system:
> 2:ino:si:ino;0:shadow,*?S
SEE ALSO
ufs(4FS),
dir_ufs(5),
attributes(7),
clri(8),
fsck_ufs(8)WARNINGS
Since
fsdb reads the disk raw, extreme caution is advised in determining
its availability of
fsdb on the system. Suggested permissions are 600 and
owned by bin.
NOTES
The old command line syntax for clearing i-nodes using the ufs-specific
'-z i-number' option is still supported by the new debugger, though it is
obsolete and will be removed in a future release. Use of this flag will
result in correct operation, but an error message will be printed warning
of the impending obsolesence of this option to the command. The
equivalent functionality is available using the more flexible
clri(8) command.
April 14, 2003
FSDB_UFS(8)