[PRINT]Unix at FIT for beginners

Unix for beginners at FIT

Access to Unix system

Students can access Unix systems from personal computers and workstations. Each user needs system account identified with logon name. Students at FIT obtain their logon name once they start their study and the logon name is valid during their stay at FIT for all computers they are granted access to (servers eva.fit.vutbr.cz, merlin.fit.vutbr.cz, computers in PC labs with Linux etc.). The list of accessible computersi can be found at www.fit.vutbr.cz/CVT/pclab.php, www.fit.vutbr.cz/CVT/unixlab.php and for servers at www.fit.vutbr.cz/CVT/servers.php. More information concerning Linux: www.fit.vutbr.cz/CVT/linux.

Logon

Unix servers traditionally use text based UI. In the old days users were connected over serial lines or modems from teletype or CRT terminals. The approach has changed, terminals are either programs on remote computer connected over network or local keyboard and monitor. However text based UI is preserved.

Logon from Windows 7/10 over network

At FIT users may run Putty program. This application emulates character-based terminal of Unix system connected over encrypte protocol ssh (acronym for Secure SHell). User can either select desired server from the list of stored profiles or type-in th server name directly. ssh rptocol is the default. Once the connection is established users is asked for login name login as:. Username is lower case in the same form you have received the credentials. Next you are asked for password, see below.

Logon from Unix/Linux over network

To logon use command ssh servername. By default ssh uses the logon name you have used in system you are connecting from. If you need logon under different username on the remote system just use the command ssh login@servername.

In the next step you are asked for password Password:.

The password is secret sequence of characters which protects your account from unauthorized use. When the password is typed in nothing is displayed so noone can read it. The password must be typed exactly the same way it was assigned to you. Since nothing is displayed when typing the password you mast take care of keyboard modifiers (CAPSlock, NumLock etc.). In case of an error you can use the <BS> (BACKSPACE) key. Note: the ley Left Arrow is not the same and cannot be used to correct typos. In case of incorrect login/password combination th message Login incorrect is shown and you are expected to try again:

login as: novak (logon name)
Password: (type in password, nothing is displayed)
... (messages, please read it)
/homes/eva/xn/xnovak00> (command prompt, now you can type your commands)

To finish your work just type the command exit or on the empty line press the CTRL-D key.

Password Change

After first logon you should change your password using command passwd. First you are prompted for current (old) password:

Old password:

As in logon procedure, when you type the password nothing is diplayed on your monitor. Then the program displays list of generated passwords and you are prompted for a new one:

New password:

Now you should type-in one of the offered passwords you have chosen. If you type something else no change is done. Otherwise you are asked to type the new password once again:

Re-enter new password:

The second entry of the new password is just for verification. You should remember the new password well since there is no way to decode it later. Even system administrator cannot do that.

You are responsible for protecting your own account. So keep the password secret. Don't save it in open form anywhere and don't disclose it to other person. Log out before you leave your terminal for longer period of time. In case you find unknown strange files in your home directory or find out your account is used by someone else immediately report this event to system administrator (postmaster@fit.vutbr.cz).

Using unencrypted protocols (telnet, ftp, ...) may be watched and your credentials may be revealed. You should use secure connection to access faculty servers, see http://www.fit.vutbr.cz/CVT/net/ssh.php.

Commands

If there is command prompt displayed you may enter a command. First type the name of a command. The command name may be followed by space and additional arguments. Following rules shoudl be followed:

  • Command name, options and parameters must be separated by at least one space.

  • Commands and most of the parameters are lowercase.

  • Both in command names and parameters lower and upper case characters are distinguished.

  • Optional paramaters begin with minus (-) sign and may not be present at all. Optional parameters modify command operation and may be grouped together, e.g. ls -la.

The command is executed by pressing <Enter> key. While writing the command you may edit the text using <BS> (BACKSPACE) key or clear the line using <CTRL-U> key. <BS> key deletes character before the cursor. Note the <BS> is not the same as left arrow key.

Special Characters

Some characters have special meaning and do not become part of command you type. Overview:

<BS> delete character before cursor.
<CTRL-U> clears the whole line.
<CTRL-D> end of input, on the beginning of the line it means end of file (EOF).
<DEL>, <CTRL-C> generates signsl INTR - normal termination of running process.
<CTRL-\> generates signal QUIT - forced termination (abortion) of running process.
<CTRL-S> temporary halt (pause) output to terminal.
<CTRL-Q> continue terminal output.

Special characters setting may be shown by command:

stty -a

On-line manual

The description of all commands, programs, functions and file formats is available with man command. The description of man command itself:

man man

Working over network

All computers are connected to local network which is connected to academic network Cesnet and Internet. Users of campus network are obliged to follow BUT netowrk use guidelines [PDF]. Available computers in local network:

eva.fit.vutbr.cz principal server for students FreeBSD
merlin.fit.vutbr.cz student server CentOS/Linux
pc[a-z][0-9][0-9][0-9]-[0-9][0-9].fit.vutbr.cz PC's in several labs and library

All information concerning computer network, operation, using network services and operational guides can be found at http://www.fit.vutbr.cz/CVT/net/

Home directory

Students' home directories reside on server eva.fit.vutbr.cz. Home directory is accessible from all Unix systems over network file system (NFS). No matter where you log in you have access to your files on Eva. Disk space for your home directory may be limited. Actual size is displayed after log in on Eva. If permited disk space is exceeded user is given a message and asked to reduce the space used. Used disk space can be found using commands:
du (directory usage)
df (free space on disk)

Home directories are backed up (usually every day). Even so you should make copies of important files, especially your projects. The lost of your files due to disk failure is not an accpetable excuse to miss a project deadline.

Disk volume is large enough (8 TB RAID-5) to keep all user's data so no disk quotas are engaged. However home directory is not intended to serve as storage for MP3s or video files. If your disk usage is beyond reasonable size disk quotas may be applied.

Electronic mail

Students may use e-mail for study and research purposes. Sending commercial information, unsolicited or annoying messages (spam) may be punished according to BUT Computer Network Operating Regulations [PDF]. Suggested reading: Internet and e-mail etiquette (http://ftp.fit.vutbr.cz/pub/doc/rfc/rfc1855.txt). Further usefull information may be found at Important Information and Guides.

Assigned student address at FIT looks like: login@stud.fit.vutbr.cz

Assigned staff address at FIT looks like: login@fit.vutbr.cz

E-mail is delivered to faculty student server eva.fit.vutbr.cz. On Unix workstations you may use program alpine or mutt. Ther other option is any IMAP4 capable client program (Thunderbird, Outlook, Android/K9-Mail, etc.) or Web interface https://email.fit.vutbr.cz/.

Reading mail

mutt program displays menu of offered commands on start. ? key shows brief description of commands. To read a mail just move using up/down arrows or type message number and hit Enter. To return back to message list pres i.

Basic commands overview

number go to message number
s store a message to another mailbox
d delete a message
m address send a new mail
r reply on current mail

Incomming mail is delivered to system mailbox. The size of this mailbox may be limited so old messages should be either moved to some other mailbox or deleted.

Command interpreter (shell)

When logged in you communicate with command intrpreter. Some usefull commands:

input and output redirection: command <input >output
commands connected through pipe: command1 | command2
previous command, next command <CTRL>P, <CTRL>N
beginning, end of a command <CTRL>A, <CTRL>E
file name completion: <ESC><ESC>, <ESC>=
set working directory: cd directory
name of working directory: pwd
show contents of a directory: ls, ls -l, ls -la
show contents of a file: pg, more, less
copy of a file: cp original copy
move or rename a file: mv original new
delete file: rm file ...
create directory: mkdir directory
delete directory: rmdir directory
list of connected users: who
disk space usage: df, du
list of running processes: ps
terminate running process: kill pid

Editor vi

Editor vi operates in two modes: insert and command mode. In insert mode almost all characters are inserted without interpretation. In command mode amlost any character represents a command. Any number before command indicates number of repetition of a command, e.g. 10a*<ESC> inserts 10 asterisks.

Switching between modes:

i start inserting before cursor
a start inserting next to cursor
o insert an empty line below cursor position and start inserting
<ESC> finish inserting, switch to command mode

Deleting commands:

x delete chracter on cursor position  
dw delete word  
dd delete line  

Moving in text:

$ jump to end of line
0 jum to start of line
fx jump to the first occurence of character x on the line
<CTRL-D> move left before automatic indent in :set ai mode
<CTRL-F> next page
<CTRL-B> previous page
numberG jump to given line
/pattern search for pattern (regular expressions are used)
n search for next occurence of the pattern

Line mode commands:

:x write changes and quit editor
:q quit without writeing changes
:e file finish editing and open another file
:n edit next file if invoked with several file names (vi *.c)
:set display and set editor parameters

Web server

Student Web server runs on server eva.fit.vutbr.cz. You may create your home page in directory $HOME/WWW, where $HOME is your home directory. Your home page is available on URL http://www.stud.fit.vutbr.cz/~login/. Main file should be named index.html or index.php. If you wish to create language dependet pages, the file names for czech and english versions should be index.php.cz and index.php.en respectively. All czech pages should be in code ISO-8859-2 (not Windows-1250)! More information may be found at http://www.fee.vutbr.cz/admin/ and http://www.fee.vutbr.cz/info/WWW/. Don't forget assign propper access rights for your files - chmod a+rX ...! Text encoding of your files may be changed using iconv program.

FTP Archive

Freely avaliable software may be obtained from server ftp.fit.vutbr.cz using anonymous ftp protocol:

ftp ftp (run a program and connect to ftp.fit.vutbr.cz)
login: anonymous
Password: e-mail
ftp> ? (commands description, ? command detailed description)
ftp> dir (list directory contents)
ftp> cd pub (change working directory)
ftp> bin (switch to binary transfer - no CR/LF conversion)
ftp> get file (transfer file to local computer)
ftp> quit (terminate connection and program)

Files are usually compressed with gzip program and combined into one file with tar. Even freely available programs are bound to specific license restriction which must be followed.

tar program

Command to use tar:

tar [key] [files]

Parameter key determines operation, files are archived files. Most commnoly used keys:

 c create archive
 x extract files from archive
 t list contents of archive
 f archive name is specified in the next parameter

Examples:

tar cvf all.tar . write all files of current directory into all.tar archive

New file with archive may be compressed:

gzip all.tar all.tar.gz is created

Compressed file is singificantly smaller than original one. When extracting files it is possible to decompress archive and then extract files using tar. The other way is this:

gzcat all.tar.gz | tar xvf -
tar xvzf all.tar.gz (alternative just for GNU and FreeBSD tar)

In case of a problem

Any requests, comments and complaints should be sent by e-mail to postmaster@fit.vutbr.cz. In case you can't log in contact propper administrator in person:

Problems with OS Linux computers should be reported to linux@fit.vutbr.cz. In your own sake you should be familiar with actual information at http://www.fit.vutbr.cz/CVT/net/.

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