Archive

Archives pour la catégorie ‘Système’

Configurer une Freebox pour autoriser une connexion VPN à un routeur DD-WRT

19/11/2018 Aucun commentaire

Source: Autour de… Sam

Autour de… Sam
freebox-revolutionLa question revient assez souvent pour se connecter à distance chez soi au travers un VPN quand on dispose d’un routeur sous DD-Wrt derrière une box ADSL.
Dans le cas que vais expliquer ci-dessous, je prendrai le cas d’une Freebox V4 et d’une Freebox V6.

Il faut tout d’abord savoir que DD-Wrt embarque un très bon parefeu et que nos box ADSL françaises sont aussi équipées d’un parefeu quand elles sont en mode routeur et non pas en mode passerelle (gateway ou bridge). Lire la suite…

Categories: Réseau, Système Tags: ,

Trucs et astuces d’utilisation de SSH

18/11/2018 Aucun commentaire

Source: Lone Wolf $cripts

SSH est l’acronyme de Secure SHell. Il s’agit historiquement du remplaçant de Telnet. Telnet est l’outil utilisé pour dialoguer simplement avec un serveur. Sa force : il peut se connecter à n’importe quoi ou presque. Ainsi, un fou utilisant telnet peut envoyer des emails (protocole SMTP), lire des pages Web (protocole HTTP), remettre sa montre à l’heure (protocole NTP), etc… Son inconvénient majeur : toutes les informations circulent en clair sur le réseau, mots de passes compris. A une époque, telnet était utilisé pour ouvrir une session à distance sur un serveur… imaginez le cauchemard. SSH est un outil dédié à l’ouverture de sessions à distances via une connexion sécurisée. Pour faire simple, SSH est à telnet ce que HTTPS est à HTTP : une version chiffrée et sécurisée. Cet article présente certaines des subtilités de SSH. Lire la suite…

Configuring Log Rotation of Apache2 and Other Logs

18/11/2018 Aucun commentaire

source: lifeonubuntu.com

I went to check out my apache2 logs

ls /var/log/apache2/

and I noticed that they were being automatically rotated (access.log, access.log.1, etc.) and compressed with gzip (access.log.2.gz, etc.). This seems to be the default Ubuntu configuration. I wanted to make find out more, and I found this helpful article about Ubuntu logs, including Apache2 Log info and some basic log rotation info.

After reading through the info, I decided that I wanted to make a few changes. The log rotation happens via the brilliantly named logrotate command. It turns out that logrotate settings kept in 2 places. Lire la suite…

How to edit and understand /etc/fstab

17/11/2018 Aucun commentaire

Source: How to edit and understand /etc/fstab

There’s a file called /etc/fstab in your Linux system. Learn what its contents mean and how it’s used in conjunction with the mount command. When you learn to understand the fstab file, you’ll be able to edit its contents yourself, too.

In this tuXfile I assume you already know how to mount filesystems and partitions with the mount command. If you don’t, I suggest reading the Mounting tuXfile before reading this one.

Author: Nana Långstedt < nana.langstedt at gmail.com >
tuXfile created: 12 October 2003
Last updated: 5 September 2009

What is fstab and why it’s useful

fstab is a configuration file that contains information of all the partitions and storage devices in your computer. The file is located under /etc, so the full path to this file is /etc/fstab.

/etc/fstab contains information of where your partitions and storage devices should be mounted and how. If you can’t access your Windows partition from Linux, aren’t able to mount your CD or write to your floppy as a normal user, or have problems with your CD-RW, you probably have a misconfigured /etc/fstab file. So, you can usually fix your mounting problems by editing yourfstab file.

/etc/fstab is just a plain text file, so you can open and edit it with any text editor you’re familiar with. However, note that you must have the root privileges before editing fstab. So, in order to edit the file, you must either log in as root or use the su command to become root.

Overview of the file

Of course everybody has a bit different /etc/fstab file because the partitions, devices and their properties are different on different systems. But the basic structure of fstab is always the same. Here’s an example of the contents of /etc/fstab:

/dev/hda2 / ext2 defaults 1 1
/dev/hdb1 /home ext2 defaults 1 2
/dev/cdrom /media/cdrom auto ro,noauto,user,exec 0 0
/dev/fd0 /media/floppy auto rw,noauto,user,sync 0 0
proc /proc proc defaults 0 0
/dev/hda1 swap swap pri=42 0 0

What does all this gibberish mean? As you see, every line (or row) contains the information of one device or partition. The first column contains the device name, the second one its mount point, third its filesystem type, fourth the mount options, fifth (a number) dump options, and sixth (another number) filesystem check options. Let’s take a closer look at this stuff.

1st and 2nd columns: Device and default mount point

The first and second columns should be pretty straightforward. They tell the mount command exactly the same things that you tell mount when you mount stuff manually: what is the device or partition, and what is the mount point. The mount point specified for a device in /etc/fstab is its default mount point. That is the directory where the device will be mounted if you don’t specify any other mount point when mounting the device.

Like you already learned from the Mounting tuXfile, most Linux distros create special directories for mount points. Most distros create them under /mnt, but some (at least SuSE) under /media. As you probably noticed when looking at the example fstab, I use SuSE’s mount points as an example.

What does all this mean? If I type the following command:

$ mount /dev/fd0… my floppy will be mounted in /media/floppy, because that’s the default mount point specified in /etc/fstab. If there is no entry for /dev/fd0 in my fstab when I issue the command above,mount gets very confused because it doesn’t know where to mount the floppy.

You can freely change the default mount points listed in /etc/fstab if you’re not satisfied with the defaults your distro has given you. Just make sure the mount point is a directory that already exists on your system. If it doesn’t, simply create it.

Some partitions and devices are also automatically mounted when your Linux system boots up. For example, have a look at the example fstab above. There are lines that look like this:

/dev/hda2 / ext2 defaults 1 1
/dev/hdb1 /home ext2 defaults 1 2

As you’ve learned, these lines mean that /dev/hda2 will be mounted to / and /dev/hdb1 to /home. This is done automatically when your Linux system boots up… if it wouldn’t, you’d have a hard time using your cool Linux system because all the programs you use are in / and you wouldn’t be able to run them if / wasn’t mounted! But how does the system know where you want to mount/dev/hda2 and /dev/hdb1? By looking at the /etc/fstab file of course.

Lire la suite…

Categories: Système Tags:

20 Linux System Monitoring Tools Every SysAdmin Should Know

17/11/2018 Aucun commentaire

monitoring toolsNeed to monitor Linux server performance? Try these built-in command and a few add-on tools. Most Linux distributions are equipped with tons of monitoring. These tools provide metrics which can be used to get information about system activities. You can use these tools to find the possible causes of a performance problem. The commands discussed below are some of the most basic commands when it comes to system analysis and debugging server issues such as:

  1. Finding out bottlenecks.
  2. Disk (storage) bottlenecks.
  3. CPU and memory bottlenecks.
  4. Network bottlenecks.

#1: top – Process Activity Command

The top program provides a dynamic real-time view of a running system i.e. actual process activity. By default, it displays the most CPU-intensive tasks running on the server and updates the list every five seconds.

top-output-269x300Commonly Used Hot Keys

The top command provides several useful hot keys:

Hot Key Usage
t Displays summary information off and on.
m Displays memory information off and on.
A Sorts the display by top consumers of various system resources. Useful for quick identification of performance-hungry tasks on a system.
f Enters an interactive configuration screen for top. Helpful for setting up top for a specific task.
o Enables you to interactively select the ordering within top.
r Issues renice command.
k Issues kill command.
z Turn on or off color/mono

Lire la suite…