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disked.txt
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1989-02-15
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Title: Using DISKED
NetWare includes utilities that directly interact with your
disk drive subsystem. These utilities include CompSurf, VRepair
and DiskEd. CompSurf is well documented and VRepair is also, to a
point, but good ole DiskEd isn't documented anywhere.
This article will deal with "moving around" in DiskEd.
Salient areas of the disk will be noted as well as how to modify
them when necessary.
First, before we get started, a word of caution, DiskEd has
the ability to "wipe out" your disk if not used without caution
and a SOLID backup. Concerning the backup, a couple good backups
are recommended "just in case" or until you feel confident enough
in your ability to work with DiskEd.
So, without further adieu, let's get acquainted with DiskEd.
Included with all versions of NetWare, DiskEd must be run at
the file server when it is down. Once down, the file server is
rebooted with DOS and then DiskEd is run. The initial screens
for DiskEd all look pretty much alike, for instance, for NetWare
86 the screen appears as such:
Novell Advanced NetWare/86 Disk Editor V2.00
(C)Copyright Novell Inc. 1983, 1984, 1985
1 disk drives are attached to this PC:
1. IBM XT or compatible
Maximum number of sectors per request = xx
>
Note that DiskEd's prompt is the ">" symbol. Notice that you
aren't told anything at first. To help alleviate this (a little)
type the letter "h", which is short for Help; DiskEd is not case
sensitive.
>h
Available commands are:
R Num Num-- Read sector for count
W Num Num-- Write sector for count
D Address-- Display Buffer from an address
C Address-- Change bytes till "."
F Byte Start End-- Fill buffer with a byte
M Start End Dest-- Move buffer to destination
N -- New drive selection *Note-Not all versions have this option
Q -- Exits to MS-DOS
* All values are Hex except "Num" in R & W
* If no values are entered on the write command
then the values of the previous read will be used
* The the buffer will hold a maximum of 64 sectors
* The default value for the sector counts is 1
and for the End values it is the buffer end.
All other values default to 0
Note that all operations discussed will be for one sector at a
time. A simple operation would be to type r0 at the prompt:
>r0 <press enter>
> <the disk "busy" light will flash and the prompt will return>
The r0 operation simply read in sector zero of track zero of the
disk. Also note that r0 only reads in one sector, you can
optionally indicate the number of sectors to read (in decimal).
For instance: r0 15 would read the first 15 sectors.
Each sector is composed of 512 bytes regardless of what
version of NetWare or what type of disk drive. Next, the data
read can be viewed by the d (display) command:
>d <press enter>
0000 FA EB 74 43 6F 70 79 72 69 67 68 74 20 28 63 29 zktCopyright (c)
...etc up to the first 256 bytes
Shown are the first 256 bytes of the 512 byte sector, if the
<enter> key is depressed at the next > prompt the next 256 bytes
will be shown. Notice the resemblance of the screen shown and
that of DOS's Debug.
Now, you may change a value(s) of anything you see. Note that you
are changing the value in memory only, you need to write it to
disk to make it permanent. When you change, you enter an address
to change. This address is relative to the sector you just read
in, so, for our previous example of r0, we enter:
>cf <press enter, note the "f" is the byte to change, in hex>
000F 29<- <right after the "-" the cursor will be waiting the
new information>
enter your change and press enter, note that you will be prompted
for the next area to change, in this case:
0010 20<-
If you are done, simply type the "." (period) and enter. To view
your change, type d0 and enter. The d0 indicates the top of the
first sector just read.
To save your change(s) permanently, (recall this was sector 0 we
read and edited) the following command would be performed:
>w0 <enter>
Note that per the "help" screen the 0 of the w0 isn't really
necessary, but gives you a good feeling inside to know for sure
which sector is being written.
In some cases you may want to wipe out some disk information. This
is handled by reading the disk sector, such as r0. Then at the
next > prompt, enter f0, which indicates fill all bytes with 0.
Now the sector just read will be full of 0s. To complete the
operation, use w0 to rewrite the sector that is now all 0s. One
reason you may want to do this is if some how the boot track
becomes corrupted. This author has seen such cases where the only
remedy was to erase the boot track and reload it (or to totally
reinitialize the disk with CompSurf!). Simply reloading it
without erasing it had no effect. Note that to actually wipe out
the boot track you need to fill all sectors of it with 0s. Those
particular sectors are noted below.
Now, we've gone over some of the basics, let's discussion some of
the salient disk sectors in the NetWare environment. All values
below are decimal (because the read and write commands use
decimal).
Sector Use
--------- ---------------------------------------------------
0 - 13 Boot area (regardless of where the disk is in the
system, this area is reserved as the boot area)
On some systems, fewer sectors are used.
14 HOTFIX redirection table (for SFT versions of NetWare)
MIRROR Tables too (best guess on this, it might be
on another sector also)
15 Indication of NetWare level, such as "NetWare" or
"Advanced NetWare" where "NetWare" is v4.61 and below.
Also contained here is the file server name (offset is
06h of sector 15)--printer info is here too
16 Map of all disk volumes on this physical disk drive.
17 Map of all disk volumes in the system (partially on
sector 16 too). (information on this sector is "best
guess")
18 Media defect table (bad block list)
19 - 31 Unknown
32 Beginning of First FAT for first volume
The FAT can be edited. For instance, you may have a file, that
you cannot delete. If you find its entry in the first FAT you can
edit the file's information. Note that two copies of the FAT
exist for each NetWare volume, regardless of version. When the
first FAT is edited, the second FAT is not updated automatically.
If the file server is booted after the first FAT has been changed,
a Mirror Mismatch error will result. But, if the volume mount is
continued, the copy of the first FAT will replace that of the
second FAT, thus restoring their equality. Below is a typical
view of some files in the FAT.
>d100
0100 00 03 46 53 57 4F 52 4B 2E 44 41 54 00 00 00 00 ..FSWORK.DAT....
0110 20 00 00 00 00 80 0C 9E 0C 9E 0C 3D 92 EE 00 5E ..........=.n.^
0120 00 03 4C 41 59 4F 55 54 2E 44 41 54 00 00 00 00 ..LAYOUT.DAT....
0130 20 00 00 00 00 80 0C 9E 0C 9E 0C 3D 92 EE 00 5D ..........=.n.]
0140 00 03 54 52 58 4C 43 4B 2E 44 41 54 00 00 00 00 ..TRXLCK.DAT....
0150 20 00 00 00 00 80 0C 9E 0C 9E 0C 3D 92 EE 00 5C ..........=.n.\
0160 00 03 43 4E 47 43 4F 41 2E 44 41 54 00 00 00 00 ..CNGCOA.DAT....
0170 20 00 00 00 00 80 0C 9E 0C 9E 0C 3D 92 EE 00 5B ..........=.n.[
Most of the data seen should not be edited. But the filename
(which starts at offset 2) can be up to 14 characters. For
instance, location 102 (above) has the first letter of the
filename, in this case the letter "F". It is not recommended that
you modify a filename to be greater than 8 characters as DOS will
have problems with it.
Note that each filename occupies 2 full rows (32 bytes) of
information. The beginning (offset 0) of the second line is the
file's attribute. The attribute shown is 20 which is
non-shareable read/write, in other words, the normal DOS attribute
given a file when created. Each file's attribute starts with 2,
this indicates a file, the remaining codes indicate if the file is
read-only, hidden, system, etc.
ok, so, that's the intro, jump in and have fun, for you tech types that is...
remember, DISKED is NOT for the faint of heart!
<<John>>