




Command:   de - disk editor
Syntax:    de [-w] block_device
           de -r file
Flags:     -r  Recover a file that has been removed
           -w  Enable writing, so device can be modified
Examples:  de -r /usr/ast/prog.c    #   Undo   the   effects   of:    rm
                                      /usr/ast/prog.c
           de -w /dev/fd0           # Edit /dev/fd0 for writing

     The de program allows a system administrator to examine and  modify
a  MINIX  file  system  device.  Commands  are  available to move to any
address  on  the  disk  and  display  the  disk  block  contents.   This
information  may  be presented in one of three visual modes: as two-byte
words, as ASCII characters or as a bit map. The disk may be searched for
a  string  of  characters.  If  the -w option is given, de will open the
device for writing and  words  may  be  modified.   Without  this  flag,
writing  is  prohibited.  Lost blocks and files can be recovered using a
variety of commands. The -r option supports automated recovery of  files
removed by unlink.

Positioning

     Disks are divided into blocks (also called 'zones') of 1024  bytes.
De  keeps  a  current  address  on the disk as a block number and a byte
offset within the block. In some visual modes the offset is rounded off,
for example, in 'word' mode the offset must be even.

     There are different types  of  blocks  on  a  file  system  device,
including  a  super  block, bit maps, i-nodes and data blocks.  De knows
the type of the current block, but will allow most positioning  commands
and visual modes to function anywhere on the disk.

     The f command (or PGDN on the keypad) moves  forward  to  the  next
block,  similarly  b (PGUP) moves backwards one block.  F (END) moves to
the last block and B (HOME) moves to the first block.

     The arrow keys (or u, d, l, and r) change the  current  address  by
small  increments.  The  size  of  the  increment depends on the current
display mode, as shown below. The various sizes suit  each  display  and
pointers move on the screen to follow each press of an arrow key.

         Mode     Up       Down     Left     Right
         Word     -2       +2       -32      +32
         Block    -64      +64      -1       +1
         Map      -256     +256     -4       +4

The g command allows movement to any specified block.  Like all commands
that  take  arguments,  a prompt and subsequent input are written to the
bottom line of the screen. Numerical entry  may  be  decimal,  octal  or
hexadecimal, for example 234, -1, 070, 0xf3, -X3C.


                                                                        



                                                                        


     While checking an i-node one may want to move to a block listed  as
a  zone  of  the  file.  The G command takes the contents at the current
address in the device as a block number and  indirectly  jumps  to  that
block.

     The address may be set  to  the  start  of  any  i-node  using  the
command  and supplying an i-node number. The I command maps a given file
name into an i-node address.  The file must exist on the current  device
and this device must be mounted.

The Display

     The first line of the display contains the device name, the name of
the  current output file (if one is open) and the current search string.
If de is being run with the -w option then the device  name  is  flagged
with '(w).' If a string is too long to fit on the line it is marked with
'...'.

     The second line contains the current block number, the total number
of  blocks,  and  the  type  of the current block.  The types are: boot,
super, i-node bit map, zone bit map, i-nodes and  data  block.   If  the
current  address  is  within  a  data  block then the string 'in use' is
displayed if the block corresponds to a set in the zone bit map.

     The third line shows the  offset  in  the  current  block.  If  the
current address is within either the i-node or zone bit maps then the i-
node or block number corresponding to the current bit is shown.  If  the
current  address is within an i-node then the i-node number and 'in use'
status is displayed.  If the address is  within  a  bit  map  or  i-node
block,  but  past  the  last  usable entry, then the string 'padding' is
shown.

     The rest of the screen is used to display  data  from  the  current
block.  There  are  three  visual  display  modes:  'word,' 'block,' and
'map.' The v command followed by w, b, or m  sets  the  current  display
mode.

     In 'word' mode 16 words, of two bytes each,  are  shown  in  either
base  2,  8, 10 or 16. The current base is displayed to the far right of
the screen. It can be changed using the o command followed by either  an
h (hexadecimal), d (decimal), o (octal) or b (binary).

     De knows where i-nodes are, and will  display  the  contents  in  a
readable  format,  including  the  rwx  bits, the user name and the time
field. If the current page is at the beginning of the super block, or an
executable  file or an ar archive, then de will also inform the user. In
all other cases the contents of the 16 words are shown to the  right  as
equivalent ASCII characters.




                                                                        



                                                                        


     In 'block' mode a whole block of 1024 bytes is displayed  as  ASCII
characters,  64  columns  by  16  lines.  Control  codes  are  shown  as
highlighted characters. If the high order bit is set in any of the  1024
bytes  then  an  'MSB' flag is shown on the far right of the screen, but
these bytes are not individually marked.

     In 'map' mode 2048 bits (256 bytes) are displayed from the  top  to
the  bottom  (32 bits) and from the left to the right of the screen. Bit
zero of a byte is towards the top of the screen.  This  visual  mode  is
generally  used  to  observe  the bit map blocks. The number of set bits
displayed is written on the far right of the screen.

Searching

     A search for an  ASCII  string  is  initiated  by  the  /  command.
Control  characters  not  used  for other purposes may be entered in the
search string, for example  CTRL-J  is  an  end-of-line  character.  The
search is from the current position to the end of the current device.

     Once a search string has been defined by  a  use  of  /,  the  next
search may be initiated with the n command, (a / followed immediately by
an ENTER is equivalent to an n).

     Whenever a search is in progress de will append one . to the prompt
line  for  every 500 blocks searched. If the string is found between the
end of the file system and the  actual  end  of  the  device,  then  the
current address is set to the end of the file system.

     Some of the positioning  commands  push  the  current  address  and
visual  mode  in  a stack before going to a new address.  These commands
are B, F, g, G, i, I, n, x and /. The p (previous) command pops the last
address  and  visual  mode  from  the stack. This stack is eight entries
deep.

Modifying the File System

     The s command will prompt for a data  word  and  store  it  at  the
current address on the disk. This is used to change information that can
not be easily changed by any other means.

     The data word is 16 bits wide, it may be entered in decimal,  octal
or  hexadecimal. Remember that the -w option must be specified for the s
command to operate. Be careful when modifying a mounted file system.

Recovering Files

     Any block on the disk may be written to an output  file.   This  is
used  to recover blocks marked as free on the disk. A write command will
request a file name the first time it is used, on subsequent writes  the
data is appended to the current output file.


                                                                        



                                                                        


     The name of the current output file is changed using the c command.
This  file should be on a different file system, to avoid overwriting an
i-node or block before it is recovered.

     An ASCII block is usually recovered using the w command.  All bytes
will have their most significant bit cleared before being written to the
output file. Bytes containing '\0' or  '\177'  are  not  copied.  The  W
command  writes  the  current  block  (1024 bytes exactly) to the output
file.

     When a file is deleted  using  unlink  the  i-node  number  in  the
directory  is  zeroed, but before its removal, it is copied into the end
of the file name field. This allows the i-node of a deleted file  to  be
found  by searching through a directory. The x command asks for the path
name of a lost file, extracts the old  i-node  number  and  changes  the
current disk address to the start of the i-node.

     Once an i-node is found, all of the freed blocks may  be  recovered
by  checking the i-node zone fields, using 'G' to go to a block, writing
it back out using 'w', going back to the i-node with p and advancing  to
the next block. This file extraction process is automated by using the X
command, which goes through the i-node,  indirect  and  double  indirect
blocks  finding  all the block pointers and recovering all the blocks of
the file.

     The X command closes the current output file and asks for the  name
of  a new output file. All of the disk blocks must be marked as free, if
they are not the command stops and the file must be recovered manually.

     When extracting lost blocks de will maintain 'holes' in  the  file.
Thus,  a  recovered sparse file does not allocate unused blocks and will
keep its efficient storage scheme.  This property of the X  command  may
be used to move a sparse file from one device to another.

     Automatic recovery may be initiated by the -r option on the command
line.  Also specified is the path name of a file just removed by unlink.
De determines which mounted file system device held the file  and  opens
it  for  reading.  The  lost  i-node  is found and the file extracted by
automatically performing an x and an X command.

     The recovered file will be written  to  /tmp.  De  will  refuse  to
automatically  recover  a file on the same file system as /tmp. The lost
file must have belonged to the user.  If  automatic  recovery  will  not
complete, then manual recovery may be performed.

Miscellaneous

     The user can terminate a session with de by typing  q,  CTRL-D,  or
the key associated with SIGQUIT.



                                                                        



                                                                        


     The m command invokes the MINIX sh shell as a subprocess.

     For help while using de use h.

Command Summary

   PGUP     b     Back one block
   PGDN     f     Forward one block
   HOME     B     Goto first block
   END      F     Goto last block
   UP       u     Move back 2/64/256 bytes
   DOWN     d     Move forward 2/64/256 bytes
   LEFT     l     Move back 32/1/4 bytes
   RIGHT    r     Move forward 32/1/4 bytes
            g     Goto specified block
            G     Goto block indirectly
            i     Goto specified i-node
            I     Filename to i-node
            /     Search
            n     Next occurrence
            p     Previous address
            h     Help
   EOF      q     Quit
            m     MINIX shell
            v     Visual mode (w b m)
            o     Output base (h d o b)
            c     Change file name
            w     Write ASCII block
            W     Write block exactly
            x     Extract lost directory entry
            X     Extract lost file blocks
            s     Store word

NOTES:  When entering a line in response to a prompt from de there are a
couple  of  editing  characters available. The previous character may be
erased by typing CTRL-H and the whole line may be erased by typing CTRL-
U.  ENTER  terminates  the  input. If DELETE or a non-ASCII character is
typed then the command requesting the input is aborted.

     The commands G, s and X will only function if  the  current  visual
display  mode  is  'word.'  The  commands  i, I and x change the mode to
'word' on completion. The commands G and / change the mode  to  'block'.
These  restrictions  and  automatic mode conversions are intended to aid
the user.

     The 'map' mode uses special graphic characters, and only  functions
if the user is at the console.





                                                                        



                                                                        


     De generates warnings for illegal user input or if  erroneous  data
is  found  on  the  disk, for example a corrupted magic number. Warnings
appear in the middle of the screen for two  seconds,  then  the  current
page  is  redrawn.  Some  minor  errors, for example, setting an unknown
visual mode, simply  ring  the  bell.  Major  errors,  for  example  I/O
problems on the file system device cause an immediate exit from de.

     The i-node and zone bit maps are  read  from  the  device  when  de
starts up. These determine whether 'in use' or 'not in use' is displayed
in the status field at the top of the screen. The bit maps are  not  re-
read  while  using de and will become out-of-date if observing a mounted
file system.

     De requires termcap definitions for 'cm'  and  'cl'.   Furthermore,
'so' and 'se' will also be used if available. The ANSI strings generated
by the keypad arrows are recognized, as well  as  any  single  character
codes defined by 'ku', 'kd', 'kl' and 'kr'.

Author

     The de program was written by Terrence Holm.































                                                                        

