GMES_FOR_006_EN_TPZ - Linux - Start-v1.0.pptx

Agenda 1/2
• GMES Station Operating System
– CentOS 6.6
• What is an Operating System?
– Linux
• UNIX:
– The Command Line
– UNIX Terminal management: screen
– User management commands
– Disk Partitioning
– Tree Structure
– Specials characters
– Commands for directories management
– Commands for files management
– Commands for the user and groups permissions
– Commands for the processes management
– Commands for file searching
– Commands for filtering
– Directory management commands
– Compression
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31/01/2021 All rights reserved © 2021, Telespazio

Agenda 2/2
• The File System
• Rights on files
• File management commands
• Process Management
• Various useful commands
• UNIX: Accessing Documentation
• Initiation to shell
• Unix job control
• Regular Expressions
• Getting files from and to Unix
• Indoor sub-system LAN overview
• Network
3

MESA STATIONS
OPERATING SYSTEM
A GMES station is composed of the following elements:
A 2.4m or 3.7m C-band antenna (Full stations only)
One acquisition
One processing
One Visualization
A Network Switch
An UPS
All rights reserved © 2021, Telespazio
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Acquisition: CentOS 6
• CentOS is a GNU/Linux distribution. All packages, except the logo one, are compiled based
on sources from the Red Hat Enterprise Linux distribution.
• Main features:
– Resource Monitoring (allocation and management of the CPU and memory allocation)
– Process monitoring
– Media monitoring
• CentOS includes management tools available for many applications such as file
management, direct printing, date and time management, ...
5

What is an Operating System?
• Most famous examples:
– Unix, DOS, Windows, Mac OS, Linux,
OS/2, BSD, ...
• Architecture-type:
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Physical devices
Command Language
Kernel
Command Interpretor, compiler, Drivers …
applications
(Desktop tools, Mail or Web applications …)
Hardware
Operating
System
APPLICATIONS

Linux
• Properties
– Multi-tasks
– Multi-users
– Multi-machines
– Free (Open Source)
• Opening/Closure of a session
– Working with Linux means being connected to the system (logged in)
– Login:
• User identification: login and password
• User rights granted by the administrator (root)
– Logout:
• Never switch a PC off without login out and shutdown
properly
• Logout or shutdown command
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UNIX: The Command Line
• Accessing UNIX terminal
• Local : applications/accessoires/terminal
• ssh [user@]hostname
– Secure Data is encrypted over “the wire”. What we use.
– Not always available outside CU due to different versions, implementations,
platform availability.
• Log in!
3 attempts to get valid username and password right
• Show who is logged in
• w or who
• Finger
• Logout!
• exit
• CTRL-D
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UNIX terminal management: screen
Help CTRL-A ?
Copy/Scrollback CTRL-A [
Paste CTRLA ]
Lock CTRL-A x
Detach CTRL-A d
New Screen CTRL-A c
Next/Previous CTRL-A n / CTRL-A p
Reattach screen –D –A –r
List active screen -ls
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User management commands
• id returns the name of the current user
• su changes the current user to “root” who is the system administrator
• su AUser changes the current user to “Auser”
• Sudo su changes the current user to “sudo user” (root)
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Disk Partitioning
• Hard disks are « split up » in partitions:
– Commands & applications
– Users accounts and data
– Swap zone
– Temporary files
– External media (disks, usb devices, ...)
– System data
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Root directory
/
home
tmp
bin
mesaduser
.cshrc
cours docs
tp1.tex
• Login directory (home dir.): ~
• Current directory: .
• Parent directory: ..
• To know the current dir.: pwd
• List the content of a dir.: ls
(see “man ls”)
• Change of directory: cd
• Create a directory: mkdir
• Naming the access path to the tp1.tex file:
• /home/mesauser/cours/tp1.tex
Or
• : ~/cours/tp1.ex
Tree Structure
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Special characters
• Directories
'.': Current directory
'..': Parent directory
'~': Home directory
• Hidden files
Under Linux hidden files start with '.' (ex : ~/.bashrc)
• Wildcards
'?': Replace a single character
'*': Replace a string
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Directory management commands
• cd ADirectory go to ADirectory
• cd / go to root directory
• cd .. go to the parent directory
• cd $HOME: go to the home directory of current user
• pwd: returns the name of the current directory
• mkdir NewDir: creates a new dir. named NewDir
• rmdir NewDir: delete the NewDir directory
• rm -R DirToDelete: removes the DirTo Deletes directory and all sub-directories (to be used with care)
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Files
'cat' : Print file content
'file' : Give the file type
'more' / 'less' : Print file content screen by screen
‘head’ / 'tail' : Print beginning or end of a file
'touch' : change file timestamp (create an empty file)
'diff' : Compare 2 files
'wc' : Word count
'cp' : Copy a file
'mv' : Deplace/rename a file
'rm' : Remove a file (rm -rf : remove recursively a directory)
'ln' : Create a link (ln -s : create a symbolic link)
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Rights, users and groups
'chmod' : Change permission
'chown' : Change the owner
'chgrp' : Change the group
'id' : Print the current user
'su' : Change user
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Processes
'ps' : Display running process (ps -elf)
'pstree' : Display running process as tree view
'top' : System monitoring
'kill' : Send a signal to kill a process
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File searching
'find' : Search a file in a directory (find . -name 'test' -type f)
'locate' : Search a file by name
'which' : locate a command
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Filters
'grep' : Print lines matching a pattern
'sort' : Sort lines of text files
'cut' : remove sections for each line of files
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Compression
• 'tar -czvf XYZ.tgz XYZ': archive a file as tarball then compress with gzip
• 'tar -xzvf XYZ.tgz': unpack a gzipped tarball archive
• 'gzip XYZ': compress a file using gzip
• 'gunzip XYZ.gz': uncompress a file using gzip
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 Data are stored:
 In a hierarchical order
 Tree structure
 3 distinct types of files:
 Ordinary files
 Directories
 Special files (media, redirections, …)
The File System (1/2)
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The File System (2/2)
• Access to files is restricted and depends on rights granted to each user (except for the user
root who has all the rights by default)
• 3 types of users:
• Owner (user)
• Users belonging to the same group (group)
• Others (others)
• 4 types of permissions
• read (r)
• write (w)
• execution (x)
• delete (d)
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• Change permissions: chmod
chmod <class op perm, …>|nnn <fic>
• class:
u: user
g: group
o: others
a: all
• op:
=: affectation
-: delete.
+: add
• perm:
r: read
w: write
x: execute
exemples:
chmod u=rwx,g=rx,o=r tp1.tex
chmod a+x script.sh
chmod 755 script.sh
• Each permission = 1 value:
• permissions for each class
r 4
w 2
x 1
rien 0
Rights on files
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File management commands
• ls: lists the files of the current directory
• ls –l: lists the files of the current directory and shows the rights granted to each file
• file OneFile: returns the type of the file One File
• find . -name Nom_Fichier: search for a file in the current dir.
• tail Nom_Fichier: displays the 10 last lines of the file
• grep abc Nom_Fichier: searches for the “abc” string in the file
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Process Management
• A Process is a dynamic object representing a program in execution and its context.
• Characteristics:
– Identification (pid)
– Parent process identification (ppid)
– Owner (owner)
– Priority
• ps -ef: displays all active processes currently running
• ps -ef | grep Process: displays the parameters related to the execution of the process Process
• Pstree: displays the tree structure of the process
• Kill -9 <n°pid>: kills the process having the given pid
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• The ps command returns the following information:
[acquisition:~] ps
PID TT STAT TIME COMMAND
3899 p1 S 0:00.08 -zsh
4743 p1 S+ 0:00.14 emacs
4180 std S 0:00.04 -zsh
Process Id
(PID)
CPU time used
Executed command
Process state:
R actif
T blocked
P waiting page
D waiting disk
S sleep
IW swapped
Z killed
Associated Terminal
(display)
Process Management
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Process Management
• The Top command displays information related to the processes in execution
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Various useful commands
• 'man XYZ': displays help of XYZ command
• 'df': displays disk usage (df -h)
• 'ftp <ftpserver>': connects to a ftp server
• 'rsh': executes a remote command using rsh
• 'ssh': executes a remote command using ssh
• 'scp': copies a file from one machine to another one
• 'shutdown -h now': stops the machine
• 'reboot': restarts the machine
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UNIX: Accessing Documentation
• Commands are generally documented using the command man
– man pages are subdivided into various sections
– Example: Documentation of the man command
man man
– Example: Documentation of the time command
man time
– Example: Documentation of the time C library function
man 3 time
• man will present the manual page of the specified entry using more or less
– In Linux, the default is less, but can be overridden
– less presents a screen-full at a time. ‘spacebar’ moves forward, ‘b’ moves backward, ‘$’ moves
to end, ‘q’ quits, ‘?’ helps
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Initiation to shell
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• Commands syntax:
command [-option(s)] [argument(s)]
Linux shells are all case
sensitive!!

UNIX: The Shells
• The “Shell” is simply another program which provides a basic human-OS interface.
• Shells can run interactively or as a shell script
• Two main ‘flavors’ of Shells:
– Bourne created what is now known as the standard shell: “sh”, or “bourne shell”. Its syntax
roughly resembles Pascal. Its derivatives include “ksh” (“korn shell”) and now, the most widely
used, “bash” (“bourne shell”).
– One of the creators of the C language implemented the shell to have a “C-programming” like
syntax. This is called “csh” or “C-shell”. Today’s most widely used form is the very popular “tcsh”.
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Unix: SH basics
– Modifying environment variables
sh: PAGER=/usr/bin/less; export PAGER
bash: export PAGER=/usr/bin/less
tcsh: setenv PAGER /usr/bin/less
– Execute an external command (sh)
# somecommand
somecommand: command not found
# echo $PATH
/home/tim/bin:/usr/local/bin:/usr/bin:/bin
# pwd
/home/tim/bin/project1
# ./somecommand
Hello world!
# /home/tim/bin/project1/somecommand
Hello world!
# PATH=$PATH:`pwd`; export PATH
# somecommand
Hello world!
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UNIX: Bourne Shell script syntax
• The first line of a sh script must start as follows:
#!/bin/sh
• Any unquoted # is treated as the beginning of a comment until end-of-line
• Every line is first parsed for shell metacharacters. These include characters
that the shell will do something with and include:
# ‘ “ & > < $ % * [ ] ? ! ` ~ ; | , { }
• Distinct commands may be separated by end-of-line, semicolon, or comma
• Environment variables are $EXPANDED
• “Back-tick” subshells are executed and `expanded`
• Pipelines are created | joining the output of | one program | with the next one
• Any commands left over must be built in or external commands.
• An error will fail the pipeline, but the script will continue!
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Unix redirection: Lesser and Greater
filename redirects the standard output and error to the file called filename:
last | grep ^root >& root-logins.txt
less root-logins.txt
filename redirects just standard output
Don’t Clobber me! By default, > will overwrite existing files, but you can turn this
off using shell settings and/or environment variables.
Appendicitis! You can append to existing files this way:
- sh: >>filename >&1
- csh: >>&filename
• Use < to redirect a file to a command’s standard input
# cat calculation.txt
(3+2)*8
# bc < calculation.txt
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• Useful when a program does not already query the command line for files to
read
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Unix Shell Scripting: Conditional Execution
• program1 && program2
– Program 2 will execute if and only if program1 exited with a 0 status
– Example:
• project1 && echo “Project1 Finished correctly!”
• program1 || program2
– Program 2 will execute if and only if program1 exited with a non-0
status
– Example:
• project1 || echo “Project1 FAILED to complete!”
• Exit a script with an error:
• exit 1
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UNIX commands for programmers
– man –k Search man pages by topic
– time How long your program took to run
– date print out current date/time
– test Compare values, existence of files, etc
– tee Replicate output to one or more files
– diff Report differences between two files
– sdiff Report differences side-by-side
– wc Show number of lines, words in a file
– sort Sort a file line by line
– gzip Compress a file
– gunzip Uncompress it
– strings Print out ASCII strings from a (binary)
– ldd Show DLLs/SOs program is linked to
– nm Show detailed info about a binary obj
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Unix Shell scripting: foreach loops
• These are useful when you want to run the same program in
sequence with different filenames
• sh example:
for VAR in test1 test5 test7b finaltest; do
runmycode $VAR >$VAR.out
Done
• csh example:
foreach VAR ( test1 test5 test7b finaltest )
runmycode $VAR >$VAR.out
end
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Unix job control
• Start a background process:
– program1 &
– program1
Hit CTRL-Z
bg
• Where did it go?
– jobs
– Ps
• Terminate the job: kill it
– kill %jobid
– kill pid
• Bring it back into the foreground
– fg %1
• Start a job in the future
– at
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Regular Expressions
• Powerful language for specifying strings of text to be searched
and/or manipulated
• Used by
– grep “Get Regular Expression and Print” – search files line by line
– sed Simple Editing tool, right from the command line
– awk Scripting language, executes “program” on matching lines
– perl Pathological Eclectic Rubbish Lister. Powerful programming language
• Note: These are not “file-globs”. The syntax is similar, but the
semantics are slightly different!
• Cannot be used to match nested structures
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• Fundamentals:
Match the specified character unless it is a ...
. Match any character (except EOL)
[character class] Match the characters in character class.
[start-end] start to end
[^character class] Match anything except the character class
$ Match the end of the line
^ Match the beginning of the line
* Match the preceding expression zero or
more times
? Match the preceding zero or one time
| Match the left hand side OR the right side (regexp)
Group the regular expression
Treat next character literally (not specially)
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Regular Expressions: Summary 1/2

Regular Expressions: Summary 2/2
• Examples:
Match a line beginning with a space-padded line number and colon:
^[ t]*[0-9][0-9]*:
Match my name (various spellings):
(Tim Shelling)|(TJS)|(T. Shelling)|(Timothy J. Shelling)
Match if the line ends in a vowel or a number:
[0-9aeiou]$
Match if the line begins with anything but a vowel or a number:
^[^0-9aeiou]
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Getting files from and to Unix
Windows PC SAMBA
FTP/SFTP
DOS/Win Floppy Disk mcopy, mdir, mdel, etc
Internet FTP, ncftp
lwp-download
mail
Archives ar
tar
zip, unzip (if available)
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Local Area Network
Indoor sub-system LAN overview
44

Network
• /sbin/ifconfig lo: print loopback interface
• '/sbin/ifconfig eth0': Ethernet interface
• 'route': Show the IP routing table
• 'ping': ping an ip on the network
• 'system-config-network': Configure network interface
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