You know, Linux is a powerful operating system, which is a bitch to maintain.
I started with Slackware some four years ago but didn't get anything done
because nothing worked and there were no information available (on how to
obtain the information that had to exist somewhere) about how to set up your
Linux. Two and half years ago I started to work at Tuorla Observatory and
others set up the system (RedHat 4.2) for me. I must say, that although there
are things that Windows does (much) better than Linux and others that you can
not do at all in Linux, Linux is a dream-come-true when it comes to operating
within Internet and creating and running your own programmes. For those of you
who have just started your Linux life and those (like me) who need to be
reminded of the simple things over and over again, I created this page of the
simple Linux hints for beginners.
These bits and pieces of information are not in any sensible order. The bit
you are looking for may be buried somewhere in midst of it all. Some of these
things can be done in an easier way with some fancy RedHad5 X-gadgets, but
should work in there as well.
Commands, Keyboard Shortcuts, and Definitions
Root is the almighty superuser of the computer. He can do anything
(whilst most actions are forbidden from ordinary users) and can create or
demolish user names. So don't make him angry - alternatively, if you are the
root (e.g. in your own computer) don't let the power to get into your head.
/ is the symbol for the root directory
(root directory is the basic level of the directories, the "C:\" directory in
Linux; e.g. cd / takes the user to the root directory from anywhere).
~ is the symbol for the current users own home directory
(the usual form /home/rareko can thus be written ~ by a user named rareko and
~rareko by other users; e.g. cd ~rareko takes any user to the home
directory of rareko from any directory they happen to be in).
Command cd can be used alone in any directory to change to the user's
own home directory (e.g. user rareko can go to his home from anywhere with the
command cd instead of cd ~rareko or cd ~).
Command pwd shows the directory where you are at the moment.
Command w shows the users in the computer and their processes running
(or being inactive) at the moment.
Command finger is similar to the w above but gives slightly
different information.
Command top shows the currently running processes and updates the
information until exited from.
Command rm deletes (removes) files just as del in DOS but there
may still be weird files that start e.g. with -. These you can delete
with rm -- "-filename.ending".
Command source .bashrc runs the .bashrc file after you have made
modifications to it. Otherwise it is run when you boot your computer the next
time.
Command chown -R username directoryname changes the owner of directory
directoryname to be the user username. This is mainly a root command but may
be useful for ordinary users sometimes as well.
Command nenscript -B -fCourier10 -pPSfile.ps Filename.ending transforms
your ascii file Filename.ending into a PostScript file named PSfile.ps that
you can send to your PostScript printer. In X you can view these PS files with
GhostView.
Command lpq -Pprintername shows you the printer's job queue.
Command lpr -Pprintername PSfile.ps sends your print file PSfile.ps to
the printer.
Command lprm -Pprintername 666 removes YOUR print file with job number
666 from the print queue. Check the job number with the lpq command described
above.
Command startx --bpp 16 starts your X-windows with 16-bit colours when
normally you get only crappy 8 bits (256 colours). This can be done
automatically as well, but those of you who wish to use IRAF or some other
strange programme that requires 8-bit colours must settle with this command
every time you use X without using IRAF.
Keyboard shortcut CTRL-L empties all the garbage from your x-terminal.
Keyboard shortcut CTRL-ALT-BACKSPACE kills your X-windows session.
Command man command opens up a manual (help) file of how to use the
command command (e.g. man man gives you information on how to
use this Linux help system. N.B. There is no way of obtaining a full list of
Linux commands or a help that would tell you how to do certain job. This is
one of the reasons Linux is so hard to maintain: once you know how to do
something you can find about extra options but if you only know what you would
like to be done, you are on your own.
One Linux feature makes your life much easier than it is in DOS. When you are
starting programmes, copying files, or doing anything with filenames in the
command line, you just type in the first one or two letters of the file name
and press tabulator-key. This automatically fills in the remaining part of the
file name. If there are lots of files which start with the same letters this
procedure only fills in as far as the letters are in common with all those
files. Then you just type in one letter more of the file name you want to
access and press tabulator again.
If you are in the middle of something you can not or don't want to save at
that moment, but would need to have an another connection, you can open a
second (or third or fourth or ...) virtual terminal by keyboard shortcut
CTRL-ALT-F1, where F1 is a function key from F1 to F6. If you are in X,
the F1 is reserved and F7 returns you to where you were. Try not to start
another X in a virtual terminal if you already have one running elsewhere.
One of the handiest features of Linux is how you can copy and paste
text in and between windows. You just select the text you want to copy by
"painting" it with the left mouse button kept in bottom. When you release the
button the text is selected. Next you can move your mouse pointer to any
window and click the middle mouse button (or both buttons at the same time if
your mouse has only got two buttons). E.g. you can select text in text files,
in system messages, or in Netscape, and paste it to your email or text editor.
Internal and External Devices
As default you must mount CD ROM and other similar devices after you have
started your Linux, and you must unmount the devices after use. Here is what
to do:
To mount your CD ROM put the CD ROM into your computer and give the following
command mount -t iso9660 /dev/cdrom /mnt/cdrom where /dev/cdrom is the
file (driver?) that you are mounting (check that the file in /dev really is
called cdrom) and /mnt/cdrom is the location where you are mounting the CD
into. Now if you go to directory /mnt/cdrom you actually are reading the
contents of your CD ROM.
To unmount your CD ROM go out of any CD ROM directory (e.g. with command
cd) and give the following command umount /mnt/cdrom. Now you
can take the CD ROM out of your computer.
You may have to be the root to mount and unmount devices.
You don't have to mount and unmount your floppy drive. You can be a true Linux
user and use it as a file or directory such as cp filename.ending
/dev/fd0 (the last character is zero) or you may be a DOS addict and use
the mtools commands mdir a:, mcopy filename.ending a:,
mcopy a:\filename.ending, and mdel a:\filename.ending.
I have got an access to iOmega Zip drive both at work and at home. The
following may heavily depend on the hardware and overall configurations of the
computer but at least for me it works: To mount the Zip drive you have to have
the SCSI installed in your kernel or in a kernel module. If it is in a module
you should give the following two commands: /sbin/insmod
/lib/modules/2.0.32/scsi/scsi_mod.o, where 2.0.32 is a directory with your
current kernel version number, and /sbin/insmod
/lib/modules/2.0.32/scsi/ppa.o. Next you can mount the drive mount -t
msdos /dev/sda4 /mnt/zip (remember to have a zip disk in the drive when
you do this). To unmount the drive after the use type umount /mnt/zip.
Once again, you may have to be the root to do this.
Useful Scripts
1) Assume you want to copy all Filename1, Filename2, ... FilenameN files to be
Filename1.fit, Filename2.fit, ... FilenameN.fit. You also want to get rid of
the old files. You may give command mv Filename1 Filename1.fit for N
times, but if N is tens or hundreds or more, you are better off with this
script:
ls -la | awk '{print "mv " $9,$9 ".fit"}' | grep Fi
This prints a line on screen for all N files:
mv Filename1 Filename1.fit, which you can copy and paste (see above) so
that the lines are run as commands.
Computer and Internet Security
You may be aware of crackers and hackers. At least
you should be. They may cause damage to your valued files or crash your
computer. They are especially active in Linux world as Linux is free and
every little cracker-to-be can get it and practise with it at home.
You should always make your connections with SSH and move your files
with SCP. Using Telnet and FTP you risk letting unwanted visitors into
your computer. If your computer is at home and you use modem to make your
occational contacts to Internet, you don't need to worry about crackers too
much. But if your computer is permanently connected to the Internet, you are
in danger every second. At any time some cracker in Wyoming, Corsica, Romania,
Pakistan, Malaysia, Easter Islands, or anywhere at all can try to gain access
into YOUR computer. Once inside there is no telling what he might want to do.
To contact some other computer from your Linux computer use command: ssh
username@computername.domain (e.g. ssh rareko@oj287.astro.utu.fi).
(To contact some other computer from your Windows computer use the ssh
programme for Windows.)
To copy files from your Linux computer to some other computer use command:
scp -pr * username@computername.domain:/home/username where -p is an
option for copying the original dates and other information of the files, -r
is an option for copying subdirectories, and * denotes for all files in the
current directory. Instead of * you can give the file name you are copying and
options -p and -r can be left out.
(To copy files from your Windows computer, be unhappy, for the creators of scp
have not made a Windows scp yet. However, there is some not uncomplicated way
of linking your Windows ssh and WinFTP together so that security is
maintained. I have not tried this one out yet but when I do I'll include
instructions here.)
System information of what is going on in your computer (in relation to the
internet) can be found in /var/log where you should check the files
messages, secure, and lastlog for any unwanted contact
attempts or other unpleasantries.
Created by: Rami T. F. Rekola