Introduction Emanuele Valea <valea@lirmm.fr> LIRMM CNRS / - - PowerPoint PPT Presentation

Introduction

Emanuele Valea <valea@lirmm.fr> LIRMM CNRS / Université de Montpellier

Course Outline

• UNIX operating system: an introduction
• Basic commands
• Shell
• Tools and advanced commands
• Shell scripts

Lesson Outline

• Introduction
• The file system
• How to handle files and directories
• Basic commands

Lesson Outline

• Introduction
• The file system
• How to handle files and directories
• Basic commands

How to start a session

• To begin a session:

login: Password:

• To end a session:

CTRL-d exit logout BE CAREFUL! Unix is case sensitive

Connection to the system

• If Linux is installed on your machine:
• Just turn on your PC!
• If Linux is installed on a remote server:
• VNC
• SSH
• -X  it allows graphical interface

Connection to the system: SSH

Unix Server Your PC

Connection to the system: SSH

• If your PC runs Linux or Mac:
• From your terminal simply run:
• ssh [-X] [<username>@]<hostname>
• -X  it allows graphical interface
• If your PC runs Windows, you must use external

programs:

• PuTTY
• MobaXterm

Connection to the system: VNC

VNC Viewer VNC Server

VNC Server (under Linux)

• Connect to the VNC Server using SSH
• Run the server:
• vncserver –geometry 1280x1024 –depth 24
• For the first execution you have to enter a password

(that will be used to authenticate the client)

• It will show a number (for instance “:3”) that

represents the display number

VNC Viewer

• Just run the VNC viewer
• Put the address of the server, including the display

number

• Example: <hostame>:<display_number>
• Put your username
• Use the password you configured in the server

VNC Server (some hints)

• Use:
• vncserver –kill :display
• to kill the server for the specified display
• Example:
• vncserver –kill :3
• Use vncpasswd to change the password

Connection to the system

• Try for yourselves!

Basic characteristic

• Multiuser: for each user:
• username
• uid
• gid
• password
• Multiprocess

There is the special user “root”

Command syntax in UNIX

• command [-options] [arguments]
• It is possible to execute more than one command

using the character “;” command1 ; command2 ; ... Commands are executed one after the other

Manual

• All Unix commands are documented:
• man <command>
• apropos <topic>
• whatis <command>
• All man pages can be easily found on the internet!

Getting help

• One thing to remember:
• If I have a problem, it is VERY LIKELY that someone has

already solved it.

• The first place where you will find solutions, are

forums on the internet

• Example: Stack Overflow, Stack Exchange, ecc…

Lesson Outline

• Introduction
• The file system
• How to handle files and directories
• Basic commands

File System

• Features:
• Hierarchic
• Directory-based File System
• Uniform (disk, directory, file)
• Hard link (same file with different names)
• Soft link (i.e., shortcut)
• File permissions

File System Hierarchy

/ bin sbin dev etc lib tmp var usr adm spool tmp bin etc include lib man local

Directory handling

• ls
• It shows the content of the current (or work) directory
• cd <dir>
• It changes the current directory
• pwd
• Print Work Directory
• mkdir <dir>
• It creates a directory
• rmdir <dir>
• It removes a directory (dir must be empty)

Directory handling

• The father of a directory is called ‘..’
• Example: cd ..  go back to the upper level in the

directory tree.

• The list of files and directories of the directory itself

is called ‘.’

• mkdir /<dirname>  creates a directory in the

root directory

• mkdir ./<dirname>  creates a sub-directory in

the work directory

File names

• The name of the file can be a sequence of any characters
• A file is called hidden file when its name starts with ‘.’
• Special characters (for the shell):
• / \ “ ' * ; ? [ ] ( ) ~
• ! $ { } < > # @ & | <space>
• To select a file that is not in the current directory it is

necessary to specify the path:

• Absolute path: /dir1/dir2/file
• Relative path: subdir1/subdir2/file

Lesson Outline

• Introduction
• The file system
• How to handle files and directories
• Basic commands

File handling

• cp [-fir] src1 src2 ... dest
• To copy one or more files
• rm [-fir] file1 file2 …
• To delete one or more files
• mv [-fi] file1 file2 ... dest
• To move (or rename) one or more files

File handling (cont.)

• Options:
• -f it does not ask for confirmation
• -i it asks for confirmation (for each file)
• -r it works recursively on every file in sub-directories

File permission modes

• 3 permission modes:
• read (r)
• write (w)
• execute (x)
• 3 user categories:
• user (u): the owner
• group (g)
• others (o)

Directory permission modes

• Permission modes for files have different meanings:
• x: the possibility to execute the file
• r: the possibility to read the file
• w: the possibility to modify the file
• Permission modes for directories:
• x: the possibility to enter the directory
• r: the possibility to show the list of files
• w: the possibility to create and remove files

How to change the permissions

• To change the permission modes of the file:

chmod [-R] mode file

• The permission can be specified:
• as octal value:
• as symbolic string:
• +, -, =
• u(ser), g(roup), o(ther), a(ll)
• r, w, x

User Group Other 4 2 1 4 2 1 4 2 1 r w x r w x r w x

How to change the permissions (cont.)

• Examples:
• chmod 777 filename
• chmod +gx filename

Lesson Outline

• Introduction
• The file system
• How to handle files and directories
• Basic commands

ls

• List directory contents
• ls [-options] [file ...]
• Options:
• -a: do not ignore entries starting with .
• -l: use a long listing format
• -g: like -l, but do not list owner
• -r: reverse order while sorting
• -t: sort by modification time
• -R: list subdirectories recursively

ls - example

• # ls -alg ~/tmp

total 84 drwx------ 5 maino staff 512 Sep 1 16:14 . drwxr-xr-x 19 maino staff 1024 Sep 6 09:06 ..

• rw-r--r--

1 maino staff 1240 Jan 21 1992 AA.readme drwxr-x--- 2 maino staff 512 May 22 14:08 examples

• rw-------

1 maino staff 2416 Jun 30 15:24 gendata.c

• rw-------

1 maino staff 332 Jun 18 15:29 local.c drwxr-xr-x 2 maino staff 512 May 22 14:08 man

• rw-r-----

1 maino staff 27930 Mar 12 23:19 new.tex

• rw-------

1 maino staff 28077 Mar 12 22:52 numer.tex

• rw-r-----

1 maino staff 70 Jun 2 18:00 prova.tex

• rw-r-----

1 maino staff 1364 May 6 14:20 random.c

• rw-r-----

1 maino staff 62 May 6 14:21 random.h drwx------ 2 maino staff 512 May 25 14:36 testprof

Text file analysis

• Using a text editor (e.g. vi, emacs, gedit)
• cat file1 file2 …
• Writes the contents of all the files listed to the screen
• head [-n] file …
• output the first n lines of the file
• Default: n=10

Text file analysis

• tail [-n] [+n] [-f] file …
• Output the last part of the file:
• -n:

last n lines, instead of the last 10

• +n:

all but the first n lines

• -f:
• utput appended data as the file grows

Text file analysis

• pg file ...
• more file ...
• less file ...

Text file analysis

• During the visualization:
• space

next page

• CR

next line

• b

previous page

• /pattern

next page with search pattern

• ?pattern previous page with search pattern
• q

quit

File size and available space

• df [-k] [drive ...]
• It shows how much free space is left on your system
• -k: KB is used (instead of blocks of 512 bytes)
• du [-aks] <directory> …
• It prints out the amount of space occupied by a dir
• -a: detail report for each file
• -s: it recourses into any subdirectories and prints
• nly a summary
• -k: KB is used (instead of blocks of 512 bytes)

df: example

• $ df
• Filesys.

1024-bl. Used Av. Cap. Mnt

• /dev/hda3

199270 182354 6625 96% /

• /dev/hda1

61060 20967 36939 36% /usr

• /dev/hda4

199271 147953 41027 78% /home/pc

Finding a file

• find dir expression
• search for files in a directory hierarchy
• find /users -name core

Finding a file

• -name pattern
• Base of file name
• Caveat: use ‘pattern’ for regular expressions
• -type type
• File type = b(lock), c(haracter), d(irectory), l(ink), f(ile),

s(ocket)

• -user username / -group groupname

File Comparison

• cmp file1 file2
• compare two files byte by byte
• comm [-123] file1 file2
• compare two sorted files line by line
• It generates 3 columns:
• in-file1-only in-file2-only common-lines
• -1 suppress lines unique to FILE1
• -2 suppress lines unique to FILE2
• -3 suppress lines that appear in both files

File Comparison

• diff [-options] file1 file2
• compare files line by line

time

• time command
• run programs and summarize system resource usage
• Example:
• time ls -la

wc

• wc file
• Print the number of newlines, words, and bytes in

files

ftp / sftp

• It allows transferring files from/to a remote server
• ftp server
• sftp server
• Basic commands:
• cd

change directory on the remote SERVER

• ls

list files within the current directory on the remote SERVER

• binary

prepare the FTP tool to transfer binary files (applications or images)

• ascii

prepare the FTP tool to transfer ascii or text files such as .html files

• put

copy a specific file from the local machine to the remote SERVER

• get

copy a specific file from the remote SERVER to the local PC

• del

delete a specific file on the remote SERVER

• bye

end your FTP connection