SunOS man pages : fsdb_ufs (1)
Maintenance Commands fsdb_ufs(1M)
NAME
fsdb_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 dif-
ferent 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 neces-
sary 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 rou-
tine 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, 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
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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 execu-
tion. 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 com-
pleted, 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.
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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 FormattedOutput.
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/ 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. Multi-
plication 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 sin-
gle letter or digit.
= f display indicator. If f is a legitimate format specif-
ier. then the value of dot is displayed using the for-
mat specifier 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 expres-
sion e or to the ASCII representation of the quoted
(") string s. This may be useful for changing direc-
tory 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
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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, 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 inter-
preted 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 hexade-
cimal.
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
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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 suc-
cessful, 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 charac-
ters 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 overriden if override is toggled on.
prompt p
change the fsdb prompt to p. p must be surrounded by
(")s.
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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 com-
mands 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' com-
mands. 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 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 FormattedOutput.
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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 dif-
ferent ways of displaying:
?
c display as cylinder groups
i display as inodes
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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 appropri-
ately updated upon completion.
EXAMPLES
> 2000+400%(20+20)=D
will display 2010 in decimal (use of fsdb as a calcu-
lator for complex arithmetic).
> 386:ino?i
display i-number 386 in an inode format. This now
becomes the current inode.
> :ln=4
changes the link count for the current inode 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 format.
> 0:file/c
displays, in ASCII, block zero of the file associated
with the current inode.
> 2:ino,*?d
displays the first blocks worth of directory entries
for the root inode of this file system. It will stop
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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 inode. The first logical block of the file is
then displayed in ASCII.
> :sb displays the superblock of this file system.
> 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.
> 2:db:block,*?d
displays the third block of the current inode as
directory entries.
> 7:dir:nm="name"
changes the name field in the directory slot to name.
> 3c3:fragment,20:fill=0x20
get fragment 3c3 and fill 20 type elements with 0x20.
> 2050=0xffff
set the contents of address 2050 to 0xffffffff.
0xffffffff may be truncated depending on the current
type.
> 1c92434="this is some text"
will place the ASCII for the string at 1c92434.
> 2:ino:si:ino;0:shadow,*?S
displays all of the shadow inode data in the shadow
inode associated with the root inode of this file sys-
tem.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
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SEE ALSO
clri(1M), fsck_ufs(1M), dir_ufs(4), fs_ufs(4), attributes(5)
WARNINGS
Since fsdb reads the disk raw, extreme caution is advised in
determining its availability of fsdb on the system. Sug-
gested 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 flexi-
ble clri(1M) command.
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