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
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
, 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
, 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
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 e.
The amount actually incremented is dependent on the size of type
dot = dot + e * sizeof (type)
The default for e
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 1.
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 information.
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
In order to view a potentially unmounted disk in a reasonable manner, fsdb
offers the cd
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 group.
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.
[ -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 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 the directory
command), this command will allow you to change or display the directory name. For example,
will get the 7
th 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
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 completion.
EXAMPLES Example 1
Displaying in Decimal
The following command displays 2010
in decimal (use of fsdb
as a calculator for complex arithmetic):
Displaying an i-number in Inode Format
The following command displays i-number 386
in an inode format. This now becomes the current inode
Changing the Link Count
The following command changes the link count for the current inode
Incrementing the Link Count
The following command increments the link count by 1
Displaying the Creation Time
The following command displays the creation time as a hexadecimal long:
Displaying the Modification Time
The following command displays the modification time in time format:
Displaying in ASCII
The following command displays in ASCII,
block zero of the file associated with the current inode
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
Displaying Changes to the Current Inode
The following command displays changes the current inode to that associated with the 5
th 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
Displaying the Superblock
The following command displays the superblock of this file system:
Displaying the Cylinder Group
The following command displays cylinder group information and summary for cylinder group 1
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
Displaying as Directory Entries
The following command displays the third block of the current inode
as directory entries:
Changing the Name Field
The following command changes the name field in the directory slot to name
Getting and Filling Elements
The following command gets fragment 3c3
and fill 20 type
elements with 0x20
Setting the Contents of an Address
The following command sets the contents of address 2050
may be truncated depending on the current type
The following command places the ASCII
for the string at 1c92434
> 1c92434="this is some text"
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: