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:
- the current base (referred to as base),
- the current address (referred to as dot),
- the current inode (referred to as inode),
- the current count (referred to as count),
- and the current type (referred to as type).
Most commands use the preset value of dot in their
execution. For example,
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
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
> 2:ino; 0:dir?d
> 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
> :ls /
is again synonymous.
The symbols recognized by fsdb are:
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 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.
display in structured style with format specifier
f. See Formatted Output.
display in unstructured style with format specifier
f. See Formatted Output.
the value of dot.
increment the value of dot
by the expression
The amount actually incremented is dependent on the size of
dot = dot + e * sizeof (type)
The default for e is 1.
decrement the value of dot by the expression
e. See +.
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
divide the value of dot by the expression
e. See *.
restore an address saved in register name.
name must be a single letter or digit.
save an address in register name. name must
be a single letter or digit.
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
incremental assignment. The address pointed to by
dot has its contents incremented by expression e.
decremental assignment. The address pointed to by
dot has its contents decremented by expression e.
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.
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.
convert the value of dot to a block address.
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
convert the value of dot to a cylinder
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.
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]
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 an area of disk with pattern p. The area of
disk is delimited by dot and count.
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.
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.
run through the valid log entries without printing any
information and verify the layout.
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.
display the header information about the file system
logging. This shows the block allocation for the log and the data structures
on the disk.
return the physical disk block number, using the value of
dot as an offset into the log.
display all deltas between the beginning of the log (BOL)
and the end of the log (EOL).
[ -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.
toggle the value of override. Some error conditions may
be overridden if override is toggled on.
change the fsdb prompt to p. p must
be surrounded by (")s.
display the current working directory.
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.
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
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,
would increment the link count of the current inode and set
the value of dot to the address of the link count field.
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
command. For example,
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.
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.
major device number.
minor device number.
although listed here, this command actually operates on
the directory name field. Once poised at the desired directory entry (using
command), this command will allow you to change or
display the directory name. For example,
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.
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:
display as cylinder groups
display as inodes
display as directories
display as superblocks
display as shadow inode data
Example 1 Displaying in Decimal
display as bytes
display as characters
display as octal shorts or longs
display as decimal shorts or longs
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
The following command displays 2010 in decimal (use of
fsdb as a calculator for complex arithmetic):
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:
Example 3 Changing the Link Count
The following command changes the link count for the current
inode to 4:
Example 4 Incrementing the Link Count
The following command increments the link count by 1:
Example 5 Displaying the Creation Time
The following command displays the creation time as a hexadecimal
Example 6 Displaying the Modification Time
The following command displays the modification time in time
Example 7 Displaying in ASCII
The following command displays in ASCII, block zero of the
file associated with the current inode:
Example 8 Displaying the First Block's Worth of Directorty
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:
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
> 5:dir:inode; 0:file,*/c
Example 10 Displaying the Superblock
The following command displays the superblock of this file
Example 11 Displaying the Cylinder Group
The following command displays cylinder group information and
summary for cylinder group 1:
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:
Example 14 Changing the Name Field
The following command changes the name field in the directory slot
Example 15 Getting and Filling Elements
The following command gets fragment 3c3 and fill 20
type elements with 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
Example 17 Placing ASCII
The following command places the ASCII for the string at
> 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: