Help in Trying Times for Linux or Windows
January 2, 2004
as published in Plug In Magazine
Ever been caught without that "rescue disk" and
thought that everything was lost, that you have no options but to
reinstall the operating system? Well don't do it just
In this article we'll introduce you to a bootable
diskette that will allow you to salvage and/or repair files
regardless of your operating system.
Apple has done away with it for years now. My BIOS scornfully
refers to it as a legacy device. Yes, I'm talking
about the poor 3.5" floppy. It wasn't always so.
There was a time when the 3.5" reigned supreme. It was much
superior to the 5.25 " – especially if you remember
the 1541 Commodore external drive. I still shudder at the
thought. And then there was the cassette tape that you used with
the ZX-81. But now I'm really showing my age.
In any case, I recently had occasion to be very thankful to
this legacy device. My dual boot Win2K/Linux Red Hat 7.1
wouldn't boot into Linux any more. Probably something to do
with that SCSI card I recently added. Well, I thought, it's
simple enough to use my Linux boot disk and see if I can sort out
the problem. But no such floppy could be found.
Allow me a quick aside to Windows-only readers. Don't
change the channel. There is something here for you because even
though the Windows operating system can't view a Linux
partition, Linux can see Windows. I'll let you draw your
own conclusions about this fact but one thing this does mean is
that you can use Linux to salvage or repair Windows files.
To get back to our main problem, and to paraphrase an
expression, it looked like I was "up the effluent stream
with no means of propulsion". Okay, so I could boot from
the installation CD but in the spirit of the new year and not
forgetting "auld acquaintance" let's see what
we can do with only a floppy drive. Besides, as you'll see,
an irresistible temptation presented itself to me along the
Creating a Bootable Diskette
In the frantic search for my Linux Red Hat 7.1 boot disk I did
came across a vaguely remembered diskette labelled
"tomsrtbt 2.0.103". Well, could Alice resist the
bottle labelled "Drink Me"?
To answer that question you really need to know what
"tomsrtbt" is. To quote Tom, "tomsrtbt"
stands for: "Tom's floppy which has a root file system and is
also bootable." I had my boot disk ready-made but you will have
to create yours by going to http://www.toms.net/rb/.
Locate the link for downloading, find an appropriate mirror
and choose the file named "tomsrtbt-2.0.103.dos.zip"
if you wish to create your diskette under Windows or
"tomsrtbt-2.0.103.tar.gz" for Linux/Unix.
A word of warning at this point. If you are running Windows
2000 creating this diskette is a bit problematic. If you've
got a Windows 98 machine handy this provides your easiest
solution. Copy the zipped file to this machine, decompress it and
boot into DOS to create your bootable floppy. Otherwise see,
Various solutions are presented there but the next easiest seems
to be to make DOS boot disks using the resources at,
http://www.bootdisk.com and then create your Linux diskette.
A couple of final notes. This distribution of Linux does not
support the NTFS file system. There should be no problems
creating your bootable disk under Linux.
Booting From a Legacy Device
Let's assume that you have managed to create your Linux
boot diskette. Reboot using this diskette, first making sure your
BIOS is set to boot from the floppy drive.
Okay, I know it's taking a long time to load the
operating system but in the spirit of the new year use the time
to reflect on "auld acquaintance"- and be comforted
that you are not using a 5.25" drive.
Choose your language - yes you get to choose your
language if you don't want the default, and pretty soon
you'll be looking at a screen full of all the Linux
commands available. If you're a little shaky at the command
line in Linux or you are one of the fearless Windows-only users
who has followed us this far don't worry. The operating
system commands you need are limited in number and we're
going to explain them as the need arises.
At this point you can remove the diskette from the drive. You
don't need it any more because you are now running from a
RAM drive. Besides, you may want to format a diskette (Linux or
Windows) and copy files to this drive.
That blinking cursor wants you to log in. Your only choice is
to enter "root" and after that the password,
"ls" and "cd" Commands
The most basic command you'll need is "ls",
the Linux equivalent of the DOS "dir". Try it out and
you should see a list of directories (folders in Windows
terminology). If you want to see more information about these
directories then type "ls –l". The
"-l" is a switch that gives the "long"
view of your files.
Next you will want to navigate around the file system and for
this you'll need "cd". Looks familiar
doesn't it? In fact, it works exactly the same way as it
does under DOS. Use "cd" with a directory name and
that directory will become your working directory. Returning to
the parent directory is as simple as "cd .." or to go
to the root directory " cd /". Don't forget the
space or it won't work.
Mounting a Drive
By now you are probably itching to look at your Windows file
system especially if you've never seen it from Linux
before. To do this the file system needs to be mounted and in
order to be mounted it needs a mount point. What this boils down
to is that you need to create a directory and mount a specific
file system on this directory. It is conventional to create mount
points in the "mnt" directory. If you are at the root
directory and issue the command "ls" you should see
this directory. Make it your working directory by typing
"cd mnt". You'll find that there are no
subdirectories here but we are going to make one. Again the
command is identical to the DOS command. Type "mkdir
cdrive" and press enter. Now list the contents of the
current directory to see the newly created directory. There you
go. You've created a directory that will be the mount point
for the Windows file system.
Remember though that you are working with a RAM drive so the
changes you are making and directories you are creating
won't be there next time you boot from diskette.
At this point you need to know something about the way that
your hard drive is organised. If you are only running Windows and
have not partitioned your drive then your "c" drive
will be referenced from Linux as "hda1" and the
command to mount this file system is "mount /dev/hda1
/mnt/cdrive –t msdos". Try it. You'll only see
a message if you've made an error. Now change directories
to the "/mnt/cdrive" directory. Not sure where you
are? Determine your present working directory by typing
"pwd". To look at your Windows files you simply need
to change to the "/mnt/cdrive" directory and use the
"ls" command. Savour the moment if this is the first
time that you have seen a Windows partition from Linux.
If you are running Linux then I'll assume you know which
drive to mount. Again, if you only have one partition then it
will be "hda1".
You should always unmount a drive when you are finished. Your
"c" drive would be unmounted by typing "umount
/dev/hda1". Make sure the drive you are trying to unmount
is not your present working directory or you'll get a
"drive busy" error.
If you're here to salvage some files by copying them to
a diskette then you will also need to know how to mount and
format a floppy. You'll be able to format your diskette for
DOS or for Linux by first typing "fdformat
/dev/fd0H1440". To make a Linux floppy type, "mke2fs
/dev/fd0"or, alternately, "mkdosfs /dev/fd0"
for a DOS diskette. To copy files to your floppy you will again
have to mount the drive. This can be done in exactly the same way
that any other drive is mounted. First create a mount point,
let's create one called "floppy", and then
mount the drive by typing "mount –t msdos /dev/fd0
/mnt/floppy". Just drop the file type switch if you are
mounting a Linux floppy. We're now ready to copy files.
Copying files is identical regardless of the operating system.
You simply use the "cp" command specifying a source
and destination. For instance to copy the file
"fstab" in the "etc" directory to your
floppy you would simply type "cp /etc/fstab
/mnt/floppy/fstab". If you wish to copy a directory and all
its contents then you will need to know the "-r"
switch. The "r" stands for recursive and will copy
all files and directories within the directory specified.
In this way you can salvage as many files as needed from the
hard drive. Read on for more advanced commands.
In some cases you may want to run as root on your original
Linux partition. This can be done by creating a mount point for
the file system, mounting it and then using the "chroot" command.
This is exactly what I wanted to do so that I could make a boot
disk for my Red Hat 7.1 installation.
First I created a mount point for the file system. In my case
I knew that my Linux drive was device hda5 so I created a mount
point called "rh71", mounted this device and then simply typed
the command "chroot /mnt/rh71". I next changed my directory to
the "sbin" directory and typed "./mkbootdisk --device /dev/fd0
2.4.2-2" and inserted a floppy into the drive. The number
following the device is the kernel version number of my
distribution. You don't have to remember it - you can easily look
it up by examining the files in the "boot" directory.
When I was finished I changed back to "tomsrtbt"
by typing "exit" at the command line.
In very quick order, I had a boot disk for my Red Hat
installation. I could now boot into Linux and do anything else I
needed to do using X Windows.
Things do not always work out so nicely though. Sometimes you
may need to look at or change information in a file. In this case
you will have to use the text editor, "vi". I'll give you
some quick tips on using this editor though I should warn you
that I have always thought of "vi" as short for
"vi" is invoked by typing "vi" and
"enter". If there is a specific file that you wish to
edit type the name of the file after the command,
"vi". Upon start-up "vi" is in command
mode and you need to press "i" for insert if you wish
to add to or change the file. Saving your changes is done by
returning to command mode by typing "escape" followed
by ":wq". This is not an extended tutorial on using
"vi" so if you have made mistakes and want to abandon
what you've done you may quickly exit by pressing the
escape key and then ":" followed by "q!".
None of your changes will have been saved and like the new year
that has just begun, you can start over again with a clean
There are many more useful commands available – for
checking the integrity of the file system for instance –
but you would probably do well to learn a little more about Linux
before exploring them. You don't want to accidentally
reformat your drive!
The "tomsrtbt" distribution is a nice little tool if
you have trouble booting from your hard drive and don't
have a rescue disk. Using a few basic Linux commands, files can
be examined, copied or changed regardless of what operating
system you are running.
About the Author
Peter Lavin runs a Web Design/Development firm in Toronto,
Canada. He has been published in a number of magazines and online sites, including UnixReview.com, php|architect and International PHP Magazine. He is a contributor to the recently published O'Reilly book, PHP Hacks and is also the author of Object Oriented PHP, published by No Starch Press.
Please do not reproduce this article in whole or part, in any form, without obtaining written permission.