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fsdb(1M)							      fsdb(1M)

NAME    [Toc]    [Back]

     fsdb - filesystem debugger	for EFS

SYNOPSIS    [Toc]    [Back]

     fsdb [-?] [-o] [-p'string'] [-w] special

DESCRIPTION    [Toc]    [Back]

     fsdb is applicable	only to	EFS filesystems.

     fsdb can be used to patch up a damaged filesystem after a crash.  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 filesystem	tree.

     Because fsdb reads	the disk raw, it is able to circumvent normal
     filesystem	security.  It also bypasses the	buffer cache mechanism.
     Hence, it is not advisable	to use fsdb to write to	a mounted filesystem.

     The options available to fsdb are:

     -?		  Display usage.

     -o		  Override some	error conditions.

     -p'string'	  Set prompt to	string.

     -w		  Open for write.

     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.

     special is	the name of a character	device file.  fsdb searches /etc/fstab
     for the raw character device filename, if given the name of a filesystem.
     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.  Since fsdb	opens the raw device file, any write-throughs bypass
     the filesystem buffer cache, resulting in a potential mismatch between
     on-disk and buffer	cache data structures.	Hence, it is recommended that
     fsdb not be used to write to a mounted filesystem.	 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.

     Numbers are considered hexadecimal	by default.  However, the user has
     control over how data are to be displayed or accepted.  The base command
     displays or sets the input/output base.  Once set,	all input defaults to
     this base and all output is shown in this base.  The base can be
     overridden	temporarily for	input by preceding hexadecimal numbers with

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fsdb(1M)							      fsdb(1M)

     0x, 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 records 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,

	  > 2:inode

     first sets	the value of dot to 2, : alerts	the start of a command,	and
     the inode command sets inode to 2.	 A count is specified after a ,.  Once
     set, count	remains	at this	value until a new command is encountered,
     which resets the value back to 1 (the default).  So, if

	  > 2000,400/X

     is	typed, 400 hexadecimal longs are listed	from 2000, and when completed
     the value of dot is 2000 +	400 * sizeof (long).  If a carriage return is
     then typed, the output routine uses the current values of dot, count, and
     type and displays 400 more	hexadecimal longs.  An * causes	the entire
     block to be displayed.

     End of block and file are maintained by fsdb.  When displaying data as
     blocks, an	error message is displayed when	the end	of the block is
     reached.  When displaying data using the db, directory, or	file commands,
     an	error message is displayed if the end of file is reached.  This	is
     needed primarily to avoid passing the end of a directory or file and
     getting unknown and unwanted results.

     Examples showing several commands and the use of carriage return are:

	  > 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	filesystem.  Once there, subsequent carriage returns
     (or + or -) advance to subsequent entries.

     Note that:

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fsdb(1M)							      fsdb(1M)

	  > 2:inode; :ls /


	  > 2:inode
	  > :ls	/

     is	again synonymous.

EXPRESSIONS    [Toc]    [Back]

     fsdb recognizes the following symbols.  There should be no	white space
     between the symbols and the arguments.

     carriage return
	      Update the value of dot by the current value of type and display
	      using the	current	value of count.

     #	      Numeric expressions can be composed of +,	-, *, and % operators
	      (evaluated left to right)	and can	use parentheses.  Once
	      evaluated, the value of dot is updated.

     ,count   Count indicator.	The global value of count is updated to	count.
	      The value	of count remains until a new command is	run.  A	count
	      specifier	of * attempts to show a	block's	worth of information.
	      The default for count is 1.

     ?f	      Display in structured style with format specifier	f (see
	      FORMATTED	OUTPUT section).

     /f	      Display in unstructured style with format	specifier f (see
	      FORMATTED	OUTPUT section).

     .	      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 do not 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 *).

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fsdb(1M)							      fsdb(1M)

     <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	(see
	      FORMATTED	OUTPUT section), then the value	of dot is displayed
	      using format specifier f.	 Otherwise, assignment is assumed (see
	      next item).


     =[s]     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    [Toc]    [Back]

     A command must be prefixed	by a : character.  Only	enough letters of the
     command to	uniquely distinguish it	are needed.  Multiple commands can 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 IRIX counterparts (see
     individual	commands for details).	The *, ?, and [-] wildcard 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	left off, the
		 current base is displayed.  Otherwise,	the current base is
		 set to	b.  Note that this is interpreted using	the old	value
		 of base.  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.

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fsdb(1M)							      fsdb(1M)

     directory	 If the	current	inode is a directory, then the value of	dot is
		 converted to a	directory slot offset in that directory.  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) can 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.

     inode	 Convert the value of dot to an	inode address.	If successful,
		 the current value of inode is 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.

     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
		 can be	used (but, if used, must be specified before the
		 filename specifiers).	Also, as stated	above, wildcard
		 characters are	available and multiple arguments can be	given.
		 The long listing shows	only the i-number and the name;	use
		 the inode command with	?i to get more information.  The
		 output	is sorted in alphabetical order.  If either the	-R or
		 the -l	options	is used, then the files	can have a character
		 following the filename, indicating the	type of	the file.
		 Directories have a /, symbolic	links have a @,	AF_UNIX
		 address family	sockets	have a = and fifos have	an f.  Regular
		 files and block and character device files have an * if they
		 are executable.  If the file type is unknown, then a ?	is

     override	 Toggle	the value of override.	Some error conditions can be
		 overridden if override	is toggled on.

     prompt p	 Change	the fsdb prompt	to p.  p must be surrounded by double
		 quotes	(").

     pwd	 Display the current working directory.

     quit	 Quit fsdb.

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fsdb(1M)							      fsdb(1M)

     sb		 The value of dot is taken as the basic	block number and then
		 converted to the address of the superblock in that cylinder
		 group.	 As a shorthand, :sb at	the beginning of a line	sets
		 the value of dot to the superblock and	displays it in
		 superblock format.

     ! sh	 Escape	to shell.

INODE COMMANDS    [Toc]    [Back]

     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 can be used to display more easily or change	the
     particular	fields.	 The value of dot is only used by the :db, :len, and
     :off commands.  Upon completion of	the command, the value of dot is
     changed to	point to that particular field.	 For example,

	  > :ln=+1

     increments	the link count of the current inode and	set the	value of dot
     to	the address of the link	count field.  It is important to know the
     format of the disk	inode structure	and the	size and alignment of the
     respective	fields;	otherwise the output of	these commands is not
     coherent.	The disk inode structure is available in <sys/fs/efs_ino.h>.

     at	  Access time.

     ct	  Creation time.

     db	  Use the current value	of dot as an index into	the list of extents
	  stored in the	disk inode to get the starting disk block number
	  associated with the corresponding extent.  Extents number from 0 to
	  11.  In order	to display the block itself, you need to pipe this
	  result into the block	command.  For example,

	       > 1:db:block,20/X

	  gets the contents of disk block number field of extent number	1 from
	  the inode and	converts it to a block address.	 Twenty	longs are then
	  displayed in hexadecimal (see	the FORMATTED OUTPUT section).

     gen  Inode	generation number.

     gid  Group	ID.

     ln	  Link count.

     len  Use the current value	of dot as an index into	the list of extents
	  stored in the	disk inode to get the length associated	with the
	  corresponding	extent.	 Extents number	from 0 to 11.  This field is
	  one byte long.  For example,

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fsdb(1M)							      fsdb(1M)

	       > 1:len/b

	  displays the contents	of the len field of extent number 1.

     mt	  Modification time.

     md	  Mode.

     maj  Major	device number.

     min  Minor	device number.

     nex  Number of extents.

     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 allows you to change or
	  display the directory	name.  For example,

	       > 7:dir:nm="foo"

	  gets the seventh directory entry of the current inode	and changes
	  its name to foo.  Names have to be the same size as the original
	  name.	 If the	new name is smaller, it	is padded with #.  If it is
	  larger, the string is	truncated to fit and a warning message to this
	  effect is displayed.

     off  Use the current value	of dot as an index into	the list of extents
	  stored in the	disk inode to get the logical block offset associated
	  with the corresponding extent.  Extents number from 0	to 11.	This
	  field	is three bytes long.  For example,

	       > 3:off,3/b

	  displays the contents	of the off field of extent number 3.

     sz	  File size.

     uid  User ID.

FORMATTED OUTPUT    [Toc]    [Back]

     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 output only
     displays raw data.	 The following table shows the different ways of

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fsdb(1M)							      fsdb(1M)

	  c	Display	as cylinder groups
	  i	Display	as inodes
	  I	Display	as inodes (all direct extents)
	  d	Display	as directories
	  s	Display	as superblocks
	  e	Display	as extents

	  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    [Toc]    [Back]

     > :base	     Display the current input/output base (hexadecimal	by

     > :base=0xa     Change the	current	input/output base to decimal.

     > 0t2000+(0t400%(0t20+0t20))=D
		     Display 2010 in decimal (use of fsdb as a calculator for
		     complex arithmetic).  The 0t indicates that the numbers
		     are to be interpreted as decimal numbers and are
		     necessary only if the current base	is not decimal.
		     Brackets should be	used to	force ordering since fsdb does
		     not force the normal ordering of operators.  Note that %
		     is	the division symbol.

     > 386:ino?i     Display i-number 386 in an	inode format.  This now
		     becomes the current inode.

     > :ln=4	     Change the	link count for the current inode to 4.

     > :ln/x	     Display the link count as a hexadecimal short.

     > :ln=+1	     Increment the link	count by 1.

     > :sz/D	     Display the size field as a decimal long.

     > :sz/X	     Display the size field as a hexadecimal long.

     > :ct=X	     Display the creation time as a hexadecimal	long.

     > :mt=t	     Display the modification time in time format.

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fsdb(1M)							      fsdb(1M)

     > 0:db,3/b	     Display the block number of the first extent as 3 bytes.
		     The block number has to be	printed	out as bytes, because
		     of	alignment considerations.

     > 0:file/c	     Display, in ASCII,	block zero of the file associated with
		     the current inode.

     > 5:dir:inode; 0:file,*/c
		     Change the	current	inode to that associated with the
		     fifth directory entry (numbered from zero)	of the current
		     inode.  The first logical block of	the file is then
		     displayed in ASCII.

     > :sb	     Display the superblock of this filesystem.

     > 0:cg?c	     Display cylinder group information	and summary for	the
		     first cylinder group (cg number 0).

     > 7:dir:nm="name"
		     Change the	name field in the directory slot to name.

     > 2:db:block,*?d
		     Display the third block of	the current inode as directory

     > 0:db=0x43b    Change the	disk block number associated with extent 0 of
		     the inode to 0x43b.

     > 0:len=0x4     Change the	length of extent 0 to 4.

     > 1:off=0xa     Change the	logical	block offset of	extent 1 to 4.

     > 0x43b:block/X Display the first four bytes of the contents of block

     > 0x43b:block=0xdeadbeef
		     Set the contents of disk block number 0x43b to
		     0xdeadbeef.  0xdeadbeef may be truncated depending	on the
		     current type.

     > 2050=0xffffffff
		     Set the contents of address 2050 to 0xffffffff.
		     0xffffffff	may be truncated depending on the current

     > 1c92434="this is	some text"
		     Place the ASCII for the string at 1c92434.

     > 2:inode:0:db:block,*?d
		     Change the	current	inode to 2.  Take the first block
		     associated	with this (root) inode and display its
		     contents as directory entries.  It	stops prematurely if

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fsdb(1M)							      fsdb(1M)

		     the EOF is	reached.

SEE ALSO    [Toc]    [Back]

     fsck(1M), dir(4), efs(4), inode(4).

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