Databases, Systems & Networks

J’ai un projet qui utilise la base de données MySQL. Je souhaite sauvegarder la base de données tous les jours, donc j’utilise ceci:

mysqldump -h host -u user -p database de mots de passe> 'location.sql'

Je souhaite que les fichiers soient nommés avec l’horodatage, c’est-à-dire:

Aujourd’hui, le fichier sera nommé quelque chose-07-05-2014 08-00-00
Demain sera quelque chose-08-05-2014 08-00-00

Comment ajouter un timestamp formaté avec le nom de fichier exporté?

Réponse:

Une solution serait:

mysqldump -h host -u user -p password database > quelque chose-$(date +%d-%m-%Y %H %M %S).sql

%Y-%m-%d

0 */8 * * * root /usr/bin/mysqldump -h host -u user -p password database > quelque chose-$(date +%d-%m-%Y %H %M %S).sql

I► Dans cet article, nous allons aborder les commandes d’administration Linux avancé :

=> mkfifo et script permettent d’initialiser un fichier de type pipe et de récupérer à distance les commandes saisies – exemple :

Un user saisit mkfifo NOmDuFichier (tube), puis démarre le script pour enregistrer les commandes dans ce tube : script -f tube

Un second user (par SSH ou en local) saisit cat tube : le script se met en marche , tout ce qui est saisi par le 1er user est visualisé par le second user :

Le premier user peut mettre fin au scripr en saisissant CTRL+D

=> logger permet d’écrire directement dans le fichier de log principal  :

=> Write permet d’écrire directement sur le terminal d’un utilisateur connecté :

=> WALL permet d’écrire sur tous les terminaux ouverts 

wall “fermez vos pc, c’est les vacances !!!”

Source: Michel Bocciolesi

Objective

To make the configuration of iptables persistent on a Debian-based system

Background

The iptables and ip6tables commands can be used to instruct Linux to perform functions such as firewalling and network address translation, however the configuration that they create is non-persistent so is lost whenever the machine is rebooted. For most practical applications this is not the desired behaviour, so some means is needed to reinstate the configuration at boot time.

For security, the iptables configuration should be applied at an early stage of the bootstrap process: preferably before any network interfaces are brought up, and certainly before any network services are started or routing is enabled. If this is not done then there will be a window of vulnerability during which the machine is remotely accessible but not firewalled.

Scenario

Suppose you have a machine that you wish to protect using a firewall. You have written iptables and ip6tables rulesets, and wish to install them so that they will remain active if the machine is rebooted.

Lire la suite…

Shell is used for various purposes under Linux. Linux user environment is made of the following components:

• Kernel – The core of Linux operating system.
• Shell – Provides an interface between the user and the kernel.
• Terminal emulator – The xterm program is a terminal emulator for the X Window System. It allows user to enter commands and display back their results on screen. 
• Linux Desktop and Windows Manager – Linux desktop is collection of various software apps. It includes the file manger, the windows manager, the Terminal emulator and much more. KDE and Gnome are two examples of the complete desktop environment in Linux.

Login

User can login locally into the console when in runlevel # 3 or graphically when in runlevel # 5 (the level numbers may differ depending on the distribution). In both cases you need to provide username and password. Bash uses the following initialization and start-up files:

1. /etc/profile – The systemwide initialization file, executed for login shells.
2. /etc/bash.bashrc – The systemwide per-interactive-shell startup file. This is a non-standard file which may not exist on your distribution. Even if it exists, it will not be sourced unless it is done explicitly in another start-up file.
3. /etc/bash.logout – The systemwide login shell cleanup file, executed when a login shell exits.
4. $HOME/.bash_profile – The personal initialization file, executed for login shells.
5. $HOME/.bashrc – The individual per-interactive-shell startup file.
6. $HOME/.bash_logout – The individual login shell cleanup file, executed when a login shell exits.
7. $HOME/.inputrc – Individual readline initialization file.

Bash Startup Scripts

Script of commands executed at login to set up environment. For example, setup JAVA_HOME path.

Login Shell

Login shells are first shell started when you log in to the system. Login shells set environment which is exported to non-login shells. Login shell calls the following when a user logs in:

• /etc/profile runs first when a user logs in runlevel # 3 (the level numbers may differ depending on the distribution).
  • /etc/profile.d
• $HOME/.bash_profile, $HOME/.bash_login, and $HOME/.profile, runs second when a user logs in in that order. $HOME/.bash_profile calls $HOME/.bashrc, which calls /etc/bashrc (/etc/bash.bashrc).

Non-Login Shell

• When an  interactive shell that is not a login shell is started, bash reads and executes commands from /etc/bash.bashrc or /etc/bashrc and $HOME/.bashrc, if these files exist. First, it calls $HOME/.bashrc. This calls /etc/bash.bashrc, which calls /etc/profile.d.

Bash Logout Scripts

• When a login shell exits, bash reads and executes commands from the file $HOME/.bash_logout, if it exists.

Source: Cybercitiz

Arrays can be a useful tool when coding your bash scripts.  The simplest way that I can define an array is to state that an array is a variable for a multi-instance dataset.

For example, a variable is used when there is a single value from a dataset like the IP Address of a server.  However, an array can be used to store all of the IP Addresses in your server room.

Speaking of IP Addresses and bash arrays, my last article (Detect and Block WordPress Brute Force Login Attacks) includes a script which is an example of how an array can be used in bash scripting.

Because arrays can be so useful in bash scripting, I thought that I would put together the following article detailing ways of Using Bash Arrays with Examples.

Initializing Bash Arrays or Assigning Values to Arrays

For arrays to be useful, we need to be able to assign values to them.  We assign values to an array by listing the array along with its instance number as shown below.  This method will assign each instance of the array one by one.

#!/bin/bash
myarray[0]=Hello
myarray[1]=World,
myarray[3]=Happy
myarray[4]=Friday

# Display all instances of the array
echo ${myarray[*]}

We can see above that in addition to being able to assign the values one by one, we can reference all array instances with an asterisk (*).  Another way to display all instances of the array is to use the following “echo ${myarray[@]}”

We run the script and get:

$ ./arrays.sh
Hello World, Happy Friday

We can also retrieve individual instances of an array by specifying the individual array instance number.  We modify the above script slightly to retrieve a couple of the instances.

#!/bin/bash
myarray[0]=Hello
myarray[1]=World,
myarray[3]=Happy
myarray[4]=Friday

# Display all instances of the array
echo ${myarray[0]} ${myarray[4]}

We run the script again and we get:

$ ./arrays.sh
Hello Friday

Lire la suite…