From DOS/Windows to Linux HOWTO

From DOS/Windows to Linux HOWTO
By Guido Gonzato, [email protected]
v1.3.0, 15 April 1998

This HOWTO is dedicated to all the (soon to be former?) DOS and Win�
dows users who have decided to switch to Linux, the free UNIX clone.
The purpose of this document is to help the reader translate his or
her knowledge of DOS and Windows into the Linux environment, as well
as providing hints on exchanging files and resources between the two
OSes.
______________________________________________________________________

Table of Contents

1. Introduction

1.1 Is Linux Right for You?
1.2 It Is. Tell Me More
1.2.1 Introductory Concepts
1.2.2 Getting Help
1.3 Conventions

2. For the Impatient

3. Files and Programs

3.1 Files: Preliminary Notions
3.2 Symbolic Links
3.3 Permissions and Ownership
3.4 Files: Translating Commands
3.4.1 Examples
3.5 Running Programs: Multitasking and Sessions
3.6 Running Programs on Remote Computers

4. Using Directories

4.1 Directories: Preliminary Notions
4.2 Directories Permissions
4.3 Directories: Translating Commands
4.3.1 Examples

5. Floppies, Hard Disks, and the Like

5.1 Managing Devices the DOS Way
5.2 Managing Devices the UNIX Way
5.3 Backing Up

6. What About Windows?

7. Tailoring the System

7.1 System Initialisation Files
7.2 Program Initialisation Files

8. A Bit of Programming

8.1 Shell Scripts: .BAT Files on Steroids
8.2 C for Yourself

9. The Remaining 1%

9.1 Using tar & gzip
9.2 Installing Applications
9.3 Tips You Can't Do Without
9.4 Where to Find Applications
9.5 A Few Things You Couldn't Do
9.6 Common Extensions and Related Programs
9.7 Converting Files

10. The End, for Now

10.1 Copyright
10.2 Disclaimer

______________________________________________________________________

1. Introduction

1.1. Is Linux Right for You?

You want to switch from DOS/Windows to Linux? Good idea: Linux is
technically superior to DOS, Windows 95 and even Windows NT. But
beware: it might not be useful for you if you are not the right type
of user. In fact, DOS and Windows are mostly employed for games and
office productivity, while Linux gives its best at networking,
development, and scientific computing. Linux is incredibly powerful,
but learning how to harness that power takes time. Thus, if mostly
need commercial sw, or if you don't feel like learning new commands
and concepts, you had better look elsewhere.

Work is underway to make Linux simpler to use, but don't expect to be
proficient with it unless you read a lot of documentation and use it
at least for a few months. Linux won't give you instant results. In
spite of these warnings, I'm 100% confident that if you are the right
user type you'll find in Linux your computer Nirvana, and never want
to use DOS or Windows again. By the way, Linux + DOS/Win can coexist
happily on the same machine.

Prerequisites for this howto: I'll assume that

� you know the basic DOS commands and concepts;

� Linux, possibly with X Window System, is properly installed on your
PC;

� your shell---the equivalent of COMMAND.COM---is bash.

Unless specified, all information in this work is aimed at bad ol'
DOS. There is information about Windows here and there, but bear in
mind that Windows and Linux are totally different, unlike DOS that is
sort of a UNIX poor relation. Please also note that this work is
neither a complete primer nor a configuration guide!

1.2. It Is. Tell Me More

You installed Linux and the programs you needed on the PC. You gave
yourself an account (if not, type adduser now!) and Linux is running.
You've just entered your name and password, and now you are looking at
the screen thinking: ``Well, now what?''

Now, don't despair. You're almost ready to do the same things you used
to do with DOS/Win, and many more. If you were running DOS/Win instead
of Linux, you would be doing some of the following tasks:

� running programs and creating, copying, viewing, deleting,
printing, renaming files;

� CD'ing, MD'ing, RD'ing, and DIR'ring your directories;

� formatting floppies and copying files from/to them;

� tailoring the system;

� writing .BAT files and programs in your favourite language;

� the remaining 1%.

You'll be glad to know that these tasks can be accomplished under
Linux in a fashion similar to DOS. Under DOS, the average user uses
very few of the 100+ commands available: the same, up to a point,
applies to Linux.

1.2.1. Introductory Concepts

The best way to learn something new is to get your feet wet. You are
strongly encouraged to experiment and play with Linux: you can't
damage the system that way. A few points:

� first of all, how to quit Linux safely. If you see a text mode
screen, press <CTRL-ALT-DEL>, wait for the system to reboot, then
switch off the PC. If you are working under X Window System, press
<CTRL-ALT-BACKSPACE> first, then <CTRL-ALT-DEL>. Never switch off
or reset the PC directly: this could damage the file system;

� unlike DOS, Linux has built-in security mechanisms. Files and
directories have permissions associated to them; as a result, some
cannot be accessed by the normal user; (see Section ``Permissions
and Ownership''). DOS, on the contrary, will let you wipe out the
entire contents of your hard disk;

� there's a special user called ``root'': the system administrator,
with full power of life and death on the machine. If you work on
your own PC, you'll be root as well. Working as root is dangerous:
any mistake can seriously damage or destroy the system just like
with DOS/Win. Don't work as root unless absolutely necessary;

� much of the complexity of Linux comes from its extreme
configurability: virtually every feature and every application can
be tailored through one or more configuration files. Complexity is
the price to pay for power;

� redirection and piping are a side DOS feature, a very inportant one
and much more powerful under Linux. Simple commands can be strung
together to accomplish complex tasks. I strongly suggest that you
learn how to use them.

1.2.2. Getting Help

There are many ways to get help with Linux. The most important are:

� reading the documentation---I mean it. Although the HOWTO you are
reading may serve as an introduction to Linux, there are several
books that you really should read: Matt Welsh's ``Linux
Installation and Getting Started'' (
<http://sunsite.unc.edu/mdw/LDP/gs/gs.html> ), Larry Greenfield's
``Linux User Guide'' (
<ftp://sunsite.unc.edu/pub/Linux/docs/linux-doc-project/users-
guide>), and the Linux FAQ ( <http://sunsite.unc.edu/mdw/FAQ/Linux-
FAQ.html>). Feel a guilty conscience until you have read at least
one of them;

� the documentation of the packages installed on the machine is often
found in subdirectories under /usr/doc/;

� to get some help about the ``internal commands'' of the shell, type
help or, better, man bash or info bash;

� to get help on a command, type man command that invokes the manual
(``man'') page pertinent to command. Alternatively, type info
command that invokes, if available, the info page pertinent to
command. Info is a hypertext-based documentation system, perhaps
not intuitive to use at first. Finally, you may try apropos command
or whatis command. With all of these commands, press `q' to exit.

1.3. Conventions

Throughout this work, examples will often follow the following format:
<...> is a required argument, while [...] an optional one. Example:

$ tar -tf <file.tar> [> redir_file]

file.tar must be indicated, but redirection to redir_file is optional.

``RMP'' means ``please Read the Man Pages for further information''.
I can't stress enough how important reading the documentation is.

When the prompt of a command example is `#', the command can only be
performed by root.

2. For the Impatient

Want to strike out? Have a look at this table:

DOS Linux Notes
------------------------------------------------------------------------------

ATTRIB (+-)attr file chmod <mode> file completely different
BACKUP tar -Mcvf device dir/ ditto
CD dirname\ cd dirname/ almost the same syntax
COPY file1 file2 cp file1 file2 ditto
DEL file rm file beware - no undelete
DELTREE dirname rm -R dirname/ ditto
DIR ls not exactly the same syntax
DIR file /S find . -name file completely different
EDIT file vi file I think you won't like it
jstar file feels like dos' edit
FORMAT fdformat,
mount, umount quite different syntax
HELP command man command, same philosophy
info command
MD dirname mkdir dirname/ almost the same syntax
MOVE file1 file2 mv file1 file2 ditto
NUL /dev/null ditto
PRINT file lpr file ditto
PRN /dev/lp0,
/dev/lp1 ditto
RD dirname rmdir dirname/ almost the same syntax
REN file1 file2 mv file1 file2 not for multiple files
RESTORE tar -Mxpvf device different syntax
TYPE file less file much better
WIN startx poles apart!

If you need more than a table of commands, please refer to the
following sections.

3. Files and Programs

3.1. Files: Preliminary Notions

Linux has a structure of directories and files very similar to
DOS/Win's. Files have filenames that obey special rules, are stored
in directories, some are executable, and among these most have command
switches. Moreover, you can use wildcard characters, redirection, and
piping. There are only a few minor differences:

� under DOS, file names are in the so-called 8.3 form; e.g.
NOTENOUG.TXT. Under Linux we can do better. If you installed Linux
using a file system like ext2 or umsdos, you can use longer
filenames (up to 255 characters), and with more than one dot: for
example, This_is.a.VERY_long.filename. Please note that I used both
upper and lower case characters: in fact...

� upper and lower case characters in file names or commands are
different. Therefore, FILENAME.tar.gz and filename.tar.gz are two
different files. ls is a command, LS is a mistake;

� Windows 95 users, beware when using long file names under Linux.
If a file name contains spaces (not recommended but possible), you
must enclose the file name in double quotes whenever you refer to
it. For example:

$ # the following command makes a directory called "My old files"
$ mkdir "My old files"
$ ls
My old files bin tmp

Further, some characters shouldn't be used: some are !*$&.

� there are no compulsory extensions like .COM and .EXE for programs,
or .BAT for batch files. Executable files are marked by an asterisk
`*' at the end of their name when you issue the ls -F command. For
example:

$ ls -F
I_am_a_dir/ cindy.jpg cjpg* letter_to_Joe my_1st_script* old~

The files cjpg* and my_1st_script* are executables, that is ``pro�
grams''. Under DOS, backup files end in .BAK, while under Linux they
end with a tilde `~'. Further, a file whose name starts with a dot is
considered as hidden. Example: the file .I.am.a.hidden.file won't show
up after the ls command;

� DOS program switches are obtained with /switch, Linux switches with
-switch or --switch. Example: dir /s becomes ls -R. Note that many
DOS programs, like PKZIP or ARJ, use UNIX-style switches.

You can now jump to Section ``Translating Commands from DOS to
Linux'', but if I were you I'd read on.

3.2. Symbolic Links

UNIX has a type of file that doesn't exist under DOS: the symbolic
link. This can be thought of as a pointer to a file or to a
directory, and can be used instead of the file or directory it points
to; it's similar to Windows 95 shortcuts. Examples of symbolic links
are /usr/X11, which points to /usr/X11R6; /dev/modem, which points to
either /dev/cua0 or /dev/cua1.

To make a symbolic link:

$ ln -s <file_or_dir> <linkname>

Example:

$ ln -s /usr/doc/g77/DOC g77manual.txt

Now you can refer to g77manual.txt instead of /usr/doc/g77/DOC. Links
appear like this in directory listings:

$ ls -F
g77manual.txt@
$ ls -l
(various things...) g77manual.txt -> /usr/doc/g77/DOC

3.3. Permissions and Ownership

DOS files and directories have the following attributes: A (archive),
H (hidden), R (read-only), and S (system). Only H and R make sense
under Linux: hidden files start with a dot, and for the R attribute,
read on.

Under UNIX a file has ``permissions'' and an owner, who in turn
belongs to a ``group''. Look at this example:

$ ls -l /bin/ls
-rwxr-xr-x 1 root bin 27281 Aug 15 1995 /bin/ls*

The first field contains the permissions of the file /bin/ls, which
belongs to root, group bin. Leaving the remaining information aside,
remember that -rwxr-xr-x means, from left to right:

- is the file type (- = ordinary file, d = directory, l = link, etc);
rwx are the permissions for the file owner (read, write, execute); r-x
are the permissions for the group of the file owner (read, execute);
(I won't cover the concept of group, you can survive without it as
long as you're a beginner ;-) r-x are the permissions for all other
users (read, execute).

The directory /bin has permissions, too: see Section ``Directories
Permissions'' for further details. This is why you can't delete the
file /bin/ls unless you are root: you don't have the permission to do
so. To change a file's permissions, the command is:

$ chmod <whoXperm> <file>

where who is u (user, that is owner), g (group), o (other), X is
either + or -, perm is r (read), w (write), or x (execute). Common
examples of chmod use are the following:

$ chmod +x file

this sets the execute permission for the file.

$ chmod go-rw file

this removes read and write permission for everyone but the owner.

$ chmod ugo+rwx file

this gives everyone read, write, and execute permission.

# chmod +s file

this makes a so-called ``setuid'' or ``suid'' file---a file that
everyone can execute with its owner's privileges. Typically, you'll
come across root suid files; these are often important system files,
like the X server.

A shorter way to refer to permissions is with digits: rwxr-xr-x can be
expressed as 755 (every letter corresponds to a bit: --- is 0, --x is
1, -w- is 2, -wx is 3...). It looks difficult, but with a bit of
practice you'll understand the concept.

root, being the superuser, can change everyone's file permissions.
RMP.

3.4. Files: Translating Commands

On the left, the DOS commands; on the right, their Linux counterpart.

ATTRIB: chmod
COPY: cp
DEL: rm
MOVE: mv
REN: mv
TYPE: more, less, cat

Redirection and plumbing operators: < > >> |

Wildcards: * ?

nul: /dev/null

prn, lpt1: /dev/lp0 or /dev/lp1; lpr

3.4.1. Examples

DOS Linux
---------------------------------------------------------------------

C:\GUIDO>ATTRIB +R FILE.TXT $ chmod 400 file.txt
C:\GUIDO>COPY JOE.TXT JOE.DOC $ cp joe.txt joe.doc
C:\GUIDO>COPY *.* TOTAL $ cat * > total
C:\GUIDO>COPY FRACTALS.DOC PRN $ lpr fractals.doc
C:\GUIDO>DEL TEMP $ rm temp
C:\GUIDO>DEL *.BAK $ rm *~
C:\GUIDO>MOVE PAPER.TXT TMP\ $ mv paper.txt tmp/
C:\GUIDO>REN PAPER.TXT PAPER.ASC $ mv paper.txt paper.asc
C:\GUIDO>PRINT LETTER.TXT $ lpr letter.txt
C:\GUIDO>TYPE LETTER.TXT $ more letter.txt
C:\GUIDO>TYPE LETTER.TXT $ less letter.txt
C:\GUIDO>TYPE LETTER.TXT > NUL $ cat letter.txt > /dev/null
n/a $ more *.txt *.asc
n/a $ cat section*.txt | less

Notes:

� * is smarter under Linux: * matches all files except the hidden
ones; .* matches all hidden files (but also the current directory
`.' and parent directory `..': beware!); *.* matches only those
that have a '.' in the middle or that end with a dot; p*r matches
both `peter' and `piper'; *c* matches both `picked' and `peck';

� when using more, press <SPACE> to read through the file, `q' to
exit. less is more intuitive and lets you use the arrow keys;

� there is no UNDELETE, so think twice before deleting anything;

� in addition to DOS' < > >>, Linux has 2> to redirect error messages
(stderr); moreover, 2>&1 redirects stderr to stdout, while 1>&2
redirects stdout to stderr;

� Linux has another wildcard: the []. Use: [abc]* matches files
starting with a, b, c; *[I-N1-3] matches files ending with I, J, K,
L, M, N, 1, 2, 3;

� lpr <file> prints a file in background. To check the status of the
print queue, use lpq; to remove a file from the print queue, use
lprm;

� there is no DOS-like RENAME; that is, mv *.xxx *.yyy won't work.
You could try this simple script; see Section ``Shell Scripts: .BAT
Files on Steroids'' for details.

___________________________________________________________________
#!/bin/sh
# ren: rename multiple files according to several rules

if [ $# -lt 3 ] ; then
echo "usage: ren \"pattern\" \"replacement\" files..."
exit 1
fi

OLD=$1 ; NEW=$2 ; shift ; shift

for file in $*
do
new=`echo ${file} | sed s/${OLD}/${NEW}/g`
mv ${file} $new
done
___________________________________________________________________

Beware: it doesn't behave like DOS' REN, as it uses ``regular expres�
sions'' that you still don't know. Shortly, if you simply want to
change file extensions, use it as in: ren "htm$" "html" *htm. Don't
forget the $ sign.

� use cp -i and mv -i to be warned when a file is going to be
overwritten.

3.5. Running Programs: Multitasking and Sessions

To run a program, type its name as you would do under DOS. If the
directory (Section ``Using Directories'') where the program is stored
is included in the PATH (Section ``System Initialisation Files''), the
program will start. Exception: unlike DOS, under Linux a program
located in the current directory won't run unless the directory is
included in the PATH. Escamotage: being prog your program, type
./prog.

This is what the typical command line looks like:

$ command [-s1 [-s2] ... [-sn]] [par1 [par2] ... [parn]] [< input] [> output]

where -s1, ..., -sn are the program switches, par1, ..., parn are the
program parameters. You can issue several commands on the command
line:

$ command1 ; command2 ; ... ; commandn

That's all about running programs, but it's easy to go a step beyond.
One of the main reasons for using Linux is that it is a multitasking
os---it can run several programs (from now on, processes) at the same
time. You can launch processes in background and continue working
straight away. Moreover, Linux lets you have several sessions: it's
like having many computers to work on at once!

� To switch to session 1..6 on the virtual consoles, press <ALT-F1>
... <ALT-F6>

� To start a new session in the same v.c. without leaving the current
one, type su - <loginname>. Example: su - root. This is useful, for
instance, when you need to perform a task that only root can do.

� To end a session, type exit. If there are stopped jobs (see later),
you'll be warned.

� To launch a process in background, add an ampersand '&' at the end
of the command line:

$ progname [-switches] [parameters] [< input] [> output] &
[1] 123

the shell identifies the process with a job number (e.g. [1]; see
below), and with a PID (Process Identification Number; 123 in our
example).

� To see how many processes there are, type ps -ax. This will output
a list of currently running processes.

� To kill a process, type kill <PID>. You may need to kill a process
when you don't know how to quit it the right way.... Unless you're
root, you can't kill other people's processes. Sometimes, a process
will only be killed by kill -SIGKILL <PID>.

In addition, the shell allows you to stop or temporarily suspend a
process, send a process to background, and bring a process from
background to foreground. In this context, processes are called
``jobs''.

� To see how many jobs there are, type jobs. Here the jobs are
identified by their job number, not by their PID.

� To stop a process running in foreground, press <CTRL-C> (it won't
always work).

� To suspend a process running in foreground, press <CTRL-Z> (ditto).

� To send a suspended process into background, type bg <job> (it
becomes a job).

� To bring a job to foreground, type fg <job>. To foreground the last
backgrounded (is my English weird?) job, simply type fg.

� To kill a job, type kill <%job> where <job> may be 1, 2, 3,...

Using these commands you can format a disk, zip a bunch of files,
compile a program, and unzip an archive all at the same time, and
still have the prompt at your disposal. Try this with DOS! And try
with Windows, just to see the difference in performance (if it doesn't
crash, of course).

3.6. Running Programs on Remote Computers

To run a program on a remote machine whose IP address is
remote.machine.edu, you do:

$ telnet remote.machine.edu

After logging in, start your favourite program. Needless to say, you
must have a shell account on the remote machine.

If you have X11, you can even run an X application on a remote
computer, displaying it on your X screen. Let remote.machine.edu be
the remote X computer and let local.linux.box be your Linux machine.
To run from local.linux.box an X program that resides on
remote.machine.edu, do the following:

� fire up X11, start an xterm or equivalent terminal emulator, then
type:

$ xhost +remote.machine.edu
$ telnet remote.machine.edu

� after logging in, type:

remote:$ DISPLAY=local.linux.box:0.0
remote:$ progname &

(instead of DISPLAY..., you may have to write: setenv DISPLAY
local.linux.box:0.0. It depends on the remote shell.)

Et voila! Now progname will start on remote.machine.edu and will be
displayed on your machine. Don't try this over the modem though, for
it's too slow to be usable.

4. Using Directories

4.1. Directories: Preliminary Notions

We have seen the differences between files under DOS and Linux. As for
directories, under DOS the root directory is \, under Linux / is.
Similarly, nested directories are separated by \ under DOS, by / under
Linux. Example of file paths:
DOS: C:\PAPERS\GEOLOGY\MID_EOC.TEX
Linux: /home/guido/papers/geology/middle_eocene.tex

As usual, .. is the parent directory and . is the current directory.
Remember that the system won't let you cd, rd, or md everywhere you
want. Each user starts from his or her own directory called 'home',
given by the system administrator; for instance, on my PC my home dir
is /home/guido.

4.2. Directories Permissions

Directories, too, have permissions. What we have seen in Section
``Permissions and Ownership'' applies to directories as well (user,
group, and other). For a directory, rx means you can cd to that
directory, and w means that you can delete a file in the directory
(according to the file's permissions, of course), or the directory
itself.

For example, to prevent other users from snooping in /home/guido/text:

$ chmod o-rwx /home/guido/text

4.3. Directories: Translating Commands

DIR: ls, find, du
CD: cd, pwd
MD: mkdir
RD: rmdir
DELTREE: rm -R
MOVE: mv

4.3.1. Examples

DOS Linux
---------------------------------------------------------------------

C:\GUIDO>DIR $ ls
C:\GUIDO>DIR FILE.TXT $ ls file.txt
C:\GUIDO>DIR *.H *.C $ ls *.h *.c
C:\GUIDO>DIR/P $ ls | more
C:\GUIDO>DIR/A $ ls -l
C:\GUIDO>DIR *.TMP /S $ find / -name "*.tmp"
C:\GUIDO>CD $ pwd
n/a - see note $ cd
ditto $ cd ~
ditto $ cd ~/temp
C:\GUIDO>CD \OTHER $ cd /other
C:\GUIDO>CD ..\TEMP\TRASH $ cd ../temp/trash
C:\GUIDO>MD NEWPROGS $ mkdir newprogs
C:\GUIDO>MOVE PROG .. $ mv prog ..
C:\GUIDO>MD \PROGS\TURBO $ mkdir /progs/turbo
C:\GUIDO>DELTREE TEMP\TRASH $ rm -R temp/trash
C:\GUIDO>RD NEWPROGS $ rmdir newprogs
C:\GUIDO>RD \PROGS\TURBO $ rmdir /progs/turbo

Notes:

1. when using rmdir, the directory to remove must be empty. To delete
a directory and all of its contents, use rm -R (at your own risk).

2. the character '~' is a shortcut for the name of your home
directory. The commands cd or cd ~ will take you to your home
directory from wherever you are; the command cd ~/tmp will take you
to /home/your_home/tmp.

3. cd - ``undoes'' the last cd.

5. Floppies, Hard Disks, and the Like

There are two ways to manage devices under Linux: the DOS way and the
UNIX way. Take your pick.

5.1. Managing Devices the DOS Way

Most Linux distributions include the Mtools suite, a set of commands
that are perfectly equivalent to their DOS counterpart, but start with
an `m': i.e., mformat, mdir, mdel, mmd, and so on. They can even
preserve long file names, but not file permissions. If you configure
Mtools editing a file called /etc/mtools.conf (a sample is provided),
you can also access the DOS/Win partition, the CD-ROM, and the Zip
drive.

To format a fresh disk though, the mformat command won't do. As root,
you'll have to issue this command beforehand:

# fdformat /dev/fd0H1440

Note: you can't access files on the floppy with a command like, say,
less a:file.txt! This is the disadvantage of the DOS way of mounting
disks.

5.2. Managing Devices the UNIX Way

UNIX has a different way to handle devices than DOS/Win. There are no
separate volumes like A: or C:; a disk, be it a floppy or whatever,
becomes part of the local file system through an operation called
``mounting''. When you're done using the disk, before extracting it
you must ``unmount'' it.

Physically formatting a disk is one thing, making a file system on it
is another. The DOS command FORMAT A: does both things, but under
Linux there are separate commands. To format a floppy, see above; to
create a file system:

# mkfs -t ext2 -c /dev/fd0H1440

You can use minix, vfat, dos or other formats instead of ext2. Once
the disk is prepared, mount it with the command

# mount -t ext2 /dev/fd0 /mnt

specifying the right file system if you don't use ext2. Now you can
address the files in the floppy. All you used to do with A: or B: is
now done using /mnt instead. Examples:

DOS Linux
---------------------------------------------------------------------

C:\GUIDO>DIR A: $ ls /mnt
C:\GUIDO>COPY A:*.* $ cp /mnt/* .
C:\GUIDO>COPY *.ZIP A: $ cp *.zip /mnt
C:\GUIDO>EDIT A:FILE.TXT $ jstar /mnt/file.txt
C:\GUIDO>A: $ cd /mnt
A:>_ /mnt/$ _

When you've finished, before extracting the disk you must unmount it
with the command

# umount /mnt

Obviously, you have to fdformat and mkfs only unformatted disks, not
previously used ones. If you want to use the drive B:, refer to
fd1H1440 and fd1 instead of fd0H1440 and fd0 in the examples above.

Needless to say, what applies to floppies also applies to other
devices; for instance, you may want to mount another hard disk or a
CD-ROM drive. Here's how to mount the CD-ROM:

# mount -t iso9660 /dev/cdrom /mnt

This was the ``official'' way to mount your disks, but there's a trick
in store. Since it's a bit of a nuisance having to be root to mount a
floppy or a CD-ROM, every user can be allowed to mount them this way:

� as root, do the following:

# mkdir /mnt/a: ; mkdir /mnt/a ; mkdir /mnt/cdrom
# chmod 777 /mnt/a* /mnt/cd*
# # make sure that the CD-ROM device is right
# chmod 666 /dev/hdb ; chmod 666 /dev/fd*

� add in /etc/fstab the following lines:

/dev/cdrom /mnt/cdrom iso9660 ro,user,noauto 0 0
/dev/fd0 /mnt/a: msdos user,noauto 0 0
/dev/fd0 /mnt/a ext2 user,noauto 0 0

Now, to mount a DOS floppy, an ext2 floppy, and a CD-ROM:

$ mount /mnt/a:
$ mount /mnt/a
$ mount /mnt/cdrom

/mnt/a, /mnt/a:, and /mnt/cdrom can now be accessed by every user.
Remember that allowing everyone to mount disks this way is a gaping
security hole, if you care.

Two useful commands are df, which gives information on the mounted
file systems, and du dirname which reports the disk space consumed by
the directory.

5.3. Backing Up

There are several packages to help you, but the very least you can do
for a multi-volume backup is (as root):

# tar -M -cvf /dev/fd0H1440 dir_to_backup/

Make sure to have a formatted floppy in the drive, and several more
ready. To restore your stuff, insert the first floppy in the drive
and do:

# tar -M -xpvf /dev/fd0H1440

6. What About Windows?

The ``equivalent'' of Windows is the graphic system X Window System,
or X11 for short. Unlike Windows or the Mac, X11 wasn't designed for
ease of use or to look good, but just to provide graphic facilities to
UNIX workstations. These are the main differences:

� while Windows looks and feels the same all over the world, X11 does
not: it's much more configurable. X11's overall look is given by a
key component called ``window manager'', of which you have a wide
choice: fvwm, basic but nice and memory efficient, fvwm2-95,
Afterstep, and many more. The w.m. is usually invoked by a file
called .xinitrc;

� your w.m. can be configured so as a window acts as in, er, Windows:
you click on it and it comes to foreground. Another possibility is
that it comes to foreground when the mouse moves over it
(``focus''). Also, the placement of windows on the screen can be
automatic or interactive: if a strange frame appears instead of
your program, left click where you want it to appear;

� most actions can be tailored editing one or more configuration
files. Read the docs of your window manager; the configuration file
can be .fvwmrc, .fvwm2rc95, .steprc, etc. A sample configuration
file is typically found in /etc/X11/window-manager-
name/system.window-manager-name;

� X11 applications are written using special libraries (``widget
sets''); as several are available, applications look different. The
most basic ones are those that use the Athena widgets (2--D look;
xdvi, xman, xcalc); others use Motif (netscape), others still use
Tcl/Tk, XForms, Qt, Gtk, and what have you. Some---not all---of
these libraries provide roughly the same look and feel as Windows;

� well, not quite. The feel, unfortunately, can be incoherent. For
instance, if you select a line of text using the mouse and press
<BACKSPACE>, you'd expect the line to disappear, right? This
doesn't work with Athena--based apps, but it does with Motif, Qt,
Gtk, and Tcl/Tk ones;

� how the scrollbars and resizing work depends on the window manager
and the widget set. Tip: if you find that the scrollbars don't
behave as you would expect, try using the central button or the two
buttons together to move them;

� applications don't have an icon by default, but they can have many.
Most window managers feature a menu you recall by clicking on the
desktop (``root window''); needless to say, the menu can be
tailored. To change the root window appearance, use xsetroot or
xloadimage;

� the clipboard can only contain text, and behaves strange. Once
you've selected text, it's already copied to the clipboard: move
elsewhere and press the central button to paste it. There's an
application, xclipboard, that provides for multiple clipboard
buffers;

� drag and drop is an option, and is only available if you use X11
applications that support it.

To save memory, one should use applications that use the same
libraries, but this is difficult to do in practice.

The K Desktop Environment project aims at making X11 look and behave
as coherently as Windows; it's currently in early beta stage but,
believe me, it's awesome. Point your browser to <http://www.kde.org>.

7. Tailoring the System

7.1. System Initialisation Files

Two important files under DOS are AUTOEXEC.BAT and CONFIG.SYS, which
are used at boot time to initialise the system, set some environment
variables like PATH and FILES, and possibly launch a program or batch
file. Under Linux there are lots of initialisation files, some of
which you had better not tamper with until you know exactly what you
are doing. I'll tell you what the most important are, anyway:

FILES NOTES

/etc/inittab don't touch for now!
/etc/rc.d/* ditto

If all you need is setting the $PATH and other environment variables,
or you want to change the login messages or automatically launch a
program after the login, have a look at the following files:

FILES NOTES

/etc/issue sets pre-login message
/etc/motd sets post-login message
/etc/profile sets $PATH and other variables, etc.
/etc/bashrc sets aliases and functions, etc.
/home/your_home/.bashrc sets your aliases + functions
/home/your_home/.bash_profile or
/home/your_home/.profile sets environment + starts your progs

If the latter file exists (note that it is a hidden file), it will be
read after the login and the commands in it will be executed.

Example---look at this .bash_profile:

______________________________________________________________________
# I am a comment
echo Environment:
printenv | less # equivalent of command SET under DOS
alias d='ls -l' # easy to understand what an alias is
alias up='cd ..'
echo "I remind you that the path is "$PATH
echo "Today is `date`" # use the output of command 'date'
echo "Have a good day, "$LOGNAME
# The following is a "shell function"
ctgz() # List the contents of a .tar.gz archive.
{
for file in $*
do
gzip -dc ${file} | tar tf -
done
}
# end of .profile
______________________________________________________________________

$PATH and $LOGNAME, you guessed right, are environment variables.
There are many others to play with; for instance, RMP for apps like
less or bash.

7.2. Program Initialisation Files

Under Linux, virtually everything can be tailored to your needs. Most
programs have one or more initialisation files you can fiddle with,
often as a .prognamerc in your home dir. The first ones you'll want to
modify are:

� .inputrc: used by bash to define key bindings;

� .xinitrc: used by startx to initialise X Window System;

� .fvwmrc: used by the window manager fvwm.

� .joerc: used by the editor joe;

� .jedrc: used by the editor jed;

� .pinerc: used by the mail reader pine;

� .Xdefault: used by many X programs.

For all of these and the others you'll come across sooner or later,
RMP. As a final note, let me suggest that you check out the
Configuration HOWTO on
<http://sunsite.unc.edu/mdw/HOWTO/Config-HOWTO.html> .

8. A Bit of Programming

8.1. Shell Scripts: .BAT Files on Steroids

If you used .BAT files to create shortcuts of long command lines (I
did a lot), this goal can be attained by inserting appropriate alias
lines (see example above) in profile or .profile. But if your .BATs
were more complicated, then you'll love the scripting language made
available by the shell: it's as powerful as QBasic, if not more. It
has variables, structures like while, for, case, if... then... else,
and lots of other features: it can be a good alternative to a ``real''
programming language.

To write a script---the equivalent of a .BAT file under DOS---all you
have to do is write a standard ASCII file containing the instructions,
save it, then make it executable with the command chmod +x
<scriptfile>. To execute it, type its name.

A word of warning. The system editor is called vi, and in my
experience most new users find it very difficult to use. I'm not going
to explain how to use it, because I don't like it and don't use it, so
there. Suffice it here to say that:

� to insert some text, type `i' then your text;

� to delete characters, type <ESC> then `x';

� to quit vi whithout saving, type <ESC> then :q!

� to save and quit, type <ESC> then :wq.

A good beginner editor is joe: invoking it by typing jstar you'll get
the same key bindings as the DOS editor. jed in WordStar or IDE mode
is even better. Please consult Section ``Where to Find Applications''
to see where to get these editors.

Writing scripts under bash is such a vast subject it would require a
book by itself, and I will not delve into the topic any further. I'll
just give you an example of shell script, from which you can extract
some basic rules:

______________________________________________________________________
#!/bin/sh
# sample.sh
# I am a comment
# don't change the first line, it must be there
echo "This system is: `uname -a`" # use the output of the command
echo "My name is $0" # built-in variables
echo "You gave me the following $# parameters: "$*
echo "The first parameter is: "$1
echo -n "What's your name? " ; read your_name
echo notice the difference: "hi $your_name" # quoting with "
echo notice the difference: 'hi $your_name' # quoting with '
DIRS=0 ; FILES=0
for file in `ls .` ; do
if [ -d ${file} ] ; then # if file is a directory
DIRS=`expr $DIRS + 1` # DIRS = DIRS + 1
elif [ -f ${file} ] ; then
FILES=`expr $FILES + 1`
fi
case ${file} in
*.gif|*jpg) echo "${file}: graphic file" ;;
*.txt|*.tex) echo "${file}: text file" ;;
*.c|*.f|*.for) echo "${file}: source file" ;;
*) echo "${file}: generic file" ;;
esac
done
echo "there are ${DIRS} directories and ${FILES} files"
ls | grep "ZxY--!!!WKW"
if [ $? != 0 ] ; then # exit code of last command
echo "ZxY--!!!WKW not found"
fi
echo "enough... type 'man bash' if you want more info."
______________________________________________________________________

8.2. C for Yourself

Under UNIX, the system language is C, love it or hate it. Scores of
other languages (Java, FORTRAN, Pascal, Lisp, Basic, Perl, awk...) are
also available.

Taken for granted that you know C, here are a couple of guidelines for
those of you who have been spoilt by Turbo C++ or one of its DOS kin.
Linux's C compiler is called gcc and lacks all the bells and whistles
that usually accompany its DOS counterparts: no IDE, on-line help,
integrated debugger, etc. It's just a rough command-line compiler,
very powerful and efficient. To compile your standard hello.c you'll
do:

$ gcc hello.c

which will create an executable file called a.out. To give the
executable a different name, do

$ gcc -o hola hello.c

To link a library against a program, add the switch -l<libname>. For
example, to link in the math library:

$ gcc -o mathprog mathprog.c -lm

(The -l<libname> switch forces gcc to link the library
/usr/lib/lib<libname>.a; so -lm links /usr/lib/libm.a).

So far, so good. But when your prog is made of several source files,
you'll need to use the utility make. Let's suppose you have written an
expression parser: its source file is called parser.c and #includes
two header files, parser.h and xy.h. Then you want to use the routines
in parser.c in a program, say, calc.c, which in turn #includes
parser.h. What a mess! What do you have to do to compile calc.c?

You'll have to write a so-called makefile, which teaches the compiler
the dependencies between sources and objects files. In our example:

______________________________________________________________________
# This is makefile, used to compile calc.c
# Press the <TAB> key where indicated!

calc: calc.o parser.o
<TAB>gcc -o calc calc.o parser.o -lm
# calc depends on two object files: calc.o and parser.o

calc.o: calc.c parser.h
<TAB>gcc -c calc.c
# calc.o depends on two source files

parser.o: parser.c parser.h xy.h
<TAB>gcc -c parser.c
# parser.o depends on three source files

# end of makefile.
______________________________________________________________________

Save this file as Makefile and type make to compile your program;
alternatively, save it as calc.mak and type make -f calc.mak, and of
course RMP. You can invoke some help about the C functions, that are
covered by man pages, section 3; for example,

$ man 3 printf

To debug your programs, use gdb. info gdb to learn how to use it.

There are lots of libraries available; among the first you'll want to
use are ncurses, to handle textmode effects, and svgalib, to do
graphics. If you feel brave enough to tackle X11 programming, there
are libraries like the abovementioned XForms, Qt, Gtk and many others,
which make writing X11 programs a breeze. Have a look at
<http://www.xnet.com/~blatura/linapp6.html> .

Many editors can act as an IDE; emacs and jed, for instance, also
feature syntax highlighting, automatic indent and so on.
Alternatively, get the package rhide from
<ftp://sunsite.unc.edu:/pub/Linux/devel/debuggers/>. It's a Borland
IDE clone, and chances are that you'll like it.

9. The Remaining 1%

More than 1%, actually...

9.1. Using tar & gzip

Under UNIX there are some widely used applications to archive and
compress files. tar is used to make archives---it's like PKZIP but it
doesn't compress, it only archives. To make a new archive:

$ tar -cvf <archive_name.tar> <file> [file...]

To extract files from an archive:

$ tar -xpvf <archive_name.tar> [file...]

To list the contents of an archive:

$ tar -tf <archive_name.tar> | less

You can compress files using compress, which is obsolete and shouldn't
be used any more, or gzip:

$ compress <file>
$ gzip <file>

that creates a compressed file with extension .Z (compress) or .gz
(gzip). These programs can compress only one file at a time. To
decompress, use:
$ compress -d <file.Z>
$ gzip -d <file.gz>

RMP.

There are also the unarj, zip and unzip (PK??ZIP compatible)
utilities. Files with extension .tar.gz or .tgz (archived with tar,
then compressed with gzip) are as common in the UNIX world as .ZIP
files are under DOS. Here's how to list the contents of a
.tar.gz archive:

$ tar -ztf <file.tar.gz> | less

9.2. Installing Applications

First of all: installing packages is root's work. Most Linux
applications are distributed as a .tar.gz archive, which typically
will contain a directory called pkgname/ containing files and/or
subdirectories. A good rule is to install these packages from
/usr/local with the command

# tar -zxf <archive.tar.gz>

reading then the README or INSTALL file. In many cases, the package is
distributed in source, which you'll have to compile to create the
binaries; often, typing make then make installwill suffice.
Obviously, you'll need the gcc or g++ compiler.

Other archives may have to be unpacked from /; this is the case with
Slackware's .tgz archives. Other archives contain the files but not a
subdirectory. Always list the contents of the archive before
installing it.

The Debian and Red Hat distributions have their own archive format;
respectively, .deb and .rpm. The latter is gaining wide acceptance; to
install an .rpm package, type

# rpm -i package.rpm

9.3. Tips You Can't Do Without

Command completion: pressing <TAB> when issuing a command will
complete the command line for you. Example: you have to type gcc
this_is_a_long_name.c; typing gcc thi<TAB> will suffice. (If you have
other files that start with the same characters, supply enough
characters to resolve any ambiguity.)

Backscrolling: pressing <SHIFT + PAG UP> (the grey key) allows you to
backscroll a few pages, depending on how much video memory you have.

Resetting the screen: if you happen to more or cat a binary file, your
screen may end up full of garbage. To fix it, blind type reset or this
sequence of characters: echo CTRL-V ESC c RETURN.

Pasting text: in console, see below; in X, click and drag to select
the text in an xterm window, then click the middle button (or the two
buttons together if you have a two-button mouse) to paste. There is
also xclipboard (alas, only for text); don't get confused by its very
slow response.

Using the mouse: if you installed gpm, a mouse driver for the console,
you can click and drag to select text, then right click to paste the
selected text. It works across different VCs.

Messages from the kernel: have a look at /var/adm/messages or
/var/log/messages as root to see what the kernel has to tell you,
including bootup messages. The command dmesg is also handy.

9.4. Where to Find Applications

If you're wondering whether there are applications to replace your old
DOS/Win ones, I suggest that you browse the main Linux software
repositories:
<ftp://sunsite.unc.edu/pub/Linux> ,
<ftp://tsx-11.mit.edu/pub/linux> , and
<ftp://ftp.funet.fi/pub/Linux> . Another excellent place is the
``Linux Applications and Utilities Page'' at
<http://www.xnet.com/~blatura/linapps.shtml> .

9.5. A Few Things You Couldn't Do

Linux can do an awful lot of things that were cumbersome, difficult or
impossible do to with DOS/Win. Here's a short list that may whet your
appetite:

� at allows you to run programs at a specified time;

� awk is a simple yet powerful language to manipulate data files (and
not only). For example, being data.dat your multi field data file,

$ awk '$2 ~ "abc" {print $1, "\t", $4}' data.dat

prints out fields 1 and 4 of every line in data.dat whose second field
contains ``abc''.
� cron is useful to perform tasks periodically, at specified date and
time. Type man 5 crontab.

� file <filename> tells you what filename is (ASCII text, executable,
archive, etc.);

� find (see also Section ``Directories: Translating Commands'') is
one of the most powerful and useful commands. It's used to find
files that match several characteristics and perform actions on
them. General use of find is:

$ find <directory> <expression>

where <expression> includes search criteria and actions. Examples:

$ find . -type l -exec ls -l {} \;

finds all the files that are symbolic links and shows what they point
to.

$ find / -name "*.old" -ok rm {} \;

finds all the files matching the pattern and deletes them, asking for
your permission first.

$ find . -perm +111

finds all the files whose permissions match 111 (executable).

$ find . -user root

finds all the files that belong to root. Lots of possibilities
here---RMP.

� grep finds text patterns in files. For example,

$ grep -l "geology" *.tex

lists the files *.tex that contain the word ``geology''. The variant
zgrep works on gzipped files. RMP;

� regular expressions are a complex but darn powerful way of
performing search operations on text. For example, ^a[^a-
m]X{4,}txt$ matches a line that starts with `a', followed by any
character except those in the interval a-m, followed by 4 or more
`X', and ends in `txt'. You use regular expressions with advanced
editors, less, and many other applications. man grep for an
introduction.

� script <script_file> dumps the screen contents on script_file until
you issue the command exit. Useful for debugging;

� sudo allows users to perform some of root's tasks (e.g. formatting
and mounting disks; RMP);

� uname -a gives you info about your system;

� The following commands often come in handy: bc, cal, chsh, cmp,
cut, fmt, head, hexdump, nl, passwd, printf, sort, split, strings,
tac, tail, tee, touch, uniq, w, wall, wc, whereis, write, xargs,
znew. RMP.

9.6. Common Extensions and Related Programs

You may come across scores of file extensions. Excluding the more
exotic ones (i.e. fonts, etc.), here's a list of who's what:

� 1 ... 8: man pages. In the unlikely case you don't yet have it, get
man.

� arj: archive made with arj.

� dvi: output file produced by TeX (see below). xdvi to visualise it;
dvips to turn it into a PostScript .ps file.

� gz: archive made with gzip.

� info: info file (sort of alternative to man pages). Get info.

� lsm: Linux Software Map file. It's a plain ASCII file containing
the description of a package.

� ps: PostScript file. To visualise or print it get gs and,
optionally, ghostview or gv.

� rpm: Red Hat package. You can install it on any system using the
package manager rpm.

� taz, tar.Z: archive made with tar and compressed with compress.

� tgz, tar.gz: archive made with tar and compressed with gzip.

� tex: text file to submit to TeX, a powerful typesetting system.
Get the package tex, available in many distributions; but beware of
NTeX, which has corrupted fonts and is included in some Slackware
versions.

� texi: texinfo file, can produce both TeX and info files (cp.
info). Get texinfo.

� xbm, xpm, xwd: graphic file. Get xpaint.

� Z: archive made with compress.

9.7. Converting Files

If you need to exchange text files between DOS/Win and Linux, beware
of the ``end of line'' problem. Under DOS, each line of text ends with
CR/LF, while under Linux with LF. If you try to edit a DOS text file
under Linux, each line will likely end with a strange--looking `M'
character; a Linux text file under DOS will appear as a kilometric
single line with no paragraphs. There are a couple of tools, dos2unix
and unix2dos, to convert the files.

If your files contain accented characters, make sure they are made
under Windows (with Write or Notepad, say) and not under plain DOS;
otherwise, all accented characters will be screwed up.

To convert Word or WordPerfect files to plain text, the matter is a
bit trickier but possible. You'll need one of the tools that can be
found on the CTAN sites; one is <ftp://ftp.tex.ac.uk> . Get the
package word2x from the directory /pub/tex/tools/', or try one the
packages available in directory /pub/tex/support/. I've only tried
word2x, and works quite well.

10. The End, for Now

Congratulations! You have now grasped a little bit of UNIX and are
ready to start working. Remember that your knowledge of the system is
still limited, and that you are expected to do more practice with
Linux to use it comfortably. But if all you had to do was get a bunch
of applications and start working with them, what I included here is
enough.

I'm sure you'll enjoy using Linux and will keep learning more about
it---everybody does. I bet, too, that you'll never go back to DOS/Win!
I hope I made myself understood and did a good service to my 3 or 4
readers.

10.1. Copyright

Unless otherwise stated, Linux HOWTO documents are copyrighted by
their respective authors. Linux HOWTO documents may be reproduced and
distributed in whole or in part, in any medium physical or electronic,
as long as this copyright notice is retained on all copies. Commercial
redistribution is allowed and encouraged; however, the author would
like to be notified of any such distributions.

All translations, derivative works, or aggregate works incorporating
any Linux HOWTO documents must be covered under this copyright notice.
That is, you may not produce a derivative work from a HOWTO and impose
additional restrictions on its distribution. Exceptions to these rules
may be granted under certain conditions; please contact the Linux
HOWTO coordinator at the address given below.

In short, we wish to promote dissemination of this information through
as many channels as possible. However, we do wish to retain copyright
on the HOWTO documents, and would like to be notified of any plans to
redistribute the HOWTOs.

If you have questions, please contact Tim Bynum, the Linux HOWTO
coordinator, at [email protected] via email.

10.2. Disclaimer

``From DOS to Linux HOWTO'' was written by Guido Gonzato,
[email protected]. Many thanks to Matt Welsh, the author of
``Linux Installation and Getting Started'', to Ian Jackson, the author
of ``Linux frequently asked questions with answers'', to Giuseppe
Zanetti, the author of ``Linux'', to all the folks who emailed me
suggestions, and especially to Linus Torvalds and GNU who gave us
Linux.

This document is provided ``as is''. I put great effort into writing
it as accurately as I could, but you use the information contained in
it at your own risk. In no event shall I be liable for any damages
resulting from the use of this work.

Feedback is welcome. For any requests, suggestions, flames, etc., feel
free to contact me.

Enjoy Linux and life,

Guido =8-)