FSDB_UFS(1M)FSDB_UFS(1M)NAMEfsdb_ufs - ufs file system debugger
SYNOPSIS
fsdb -F ufs [generic_options] [specific_options] special
DESCRIPTION
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 sys‐
tem 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 num‐
bers 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 exam‐
ple,
> 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 speci‐
fied 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 parenthe‐
ses. 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 com‐
mand 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
FormattedOutput.
/ f
display in unstructured style with format specifier f See
FormattedOutput.
.
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. Multiplica‐
tion 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 speci‐
fier f. See FormattedOutput. 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 gov‐
erned 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 cor‐
rectness 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 con‐
verted 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 begin‐
ning 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 off‐
set 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 overri‐
den 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 con‐
verted 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 frag‐
ment 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 FormattedOutput.
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 indi‐
rect 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 trun‐
cated 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 struc‐
tured 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 com‐
pletion.
EXAMPLES
Example 1 Displaying in Decimal
The following command displays 2010 in decimal (use of fsdb as a calcu‐
lator 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 associ‐
ated 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 prema‐
turely 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 asso‐
ciated 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 ALSOclri(1M), fsck_ufs(1M), dir_ufs(4), attributes(5), ufs(7FS)WARNINGS
Since fsdb reads the disk raw, extreme caution is advised in determin‐
ing 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(1M)
command.
Apr 14, 2003 FSDB_UFS(1M)
