Debian/Ubuntu Tips and Tricks

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Debian/Ubuntu Tips and Tricks

Archive for the 'System' Category

How Tos on running a debian/ubuntu linux system from getting over troubles, configuring X, bash scripting… Anything related to your local system.

How-To: Fight SPAM with Postfix RBL

Posted by chantra on 26th September 2013

Spam, spam everywhere! If you are hosting your own mail server, fighting spam can become tricky. Antispam solutions do catch a fair amount of them, but still many spam email can still make their way through.

RBL (Real-time Blackhole) is a database of known spammy IPs which is accessible over DNS. Depending on the response received from the DNS server, the IP is classified as spammy or not.

This tutorial will show you how to set up RBL with postfix.

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Posted in Administration, HowTo, Networking, System | 1 Comment »

How-To: using Python Virtual Environments

Posted by chantra on 3rd September 2013

A nice thing about Python is that there is tons of modules available out there. Not all those modules are readily available for your distro and even if there were, chances are that a newer release with new features is already out there.

You might not always want to install those modules system wide, either because there might not be any need for it, or because they could clash with the same module install via package management.

To answer this problem, python has a virtualenv that will let you create multiple virtual python instances within which you will be able to install whichever modules you might need. All this without requiring root pribileges.

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How-To: Automatically logout idle bash session

Posted by chantra on 15th July 2013

It can be useful to have a bash session automatically closing after some time. One of the obvious reason you might want this to happen is to make sure that no console is left with root access unwillingly.

Bash comes ready for this and can be configured to automatically terminate after waiting for activity for a given time.

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Posted in Administration, General, HowTo, System | No Comments »

How-To: Make a file Immutable/Write protected

Posted by chantra on 10th June 2013

There might be time when you want to make sure that a file will be protected from accidental/automated change/deletion. While one can protect a file/directory in some ways by removing write permissions using standard file permission on Unix already can save you from some situations, there is more that can be done on Linux.

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Posted in Administration, HowTo, System | 2 Comments »

How-To: tail multiple files with multitail

Posted by chantra on 29th April 2013

Many times you will end up tailing multiple files simultaneously. There is a sweet linux utility called multitail that will let you tail multiple files at the same time within the same shell.

And not only will you be able to tail multiple files! You will also be able to run multiple commands and tail their outputs!

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How-To: Reboot on OOM

Posted by chantra on 17th April 2013

Ever had your linux box getting Out of Memory (OOM)? Cleaning up after the OOM killer kicked in to find out that even though OOM killer did a decent job at trying to kill the bad processes, your system ends up in an unknown state and you might be better of rebooting the host to make sure it comes back up in a state that you know is safe.

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Posted in Administration, HowTo, System | 1 Comment »

How-To: Bash Parameter Expansion and String Manipulation

Posted by chantra on 19th February 2013

Last time we saw how bash can help us in handling default values out of the box using parameter expansion. This time we will see how basic string operations (nonetheless common and useful) can also be achieved using bash.

There is many ways to do string manipulation with bash, like finding a filename extension using expr, separating the directory part from a filename using dirname and basename.... or even more sophisticated ones based on regex, sed....

Why using a sledgehammer to crack a nut when you could use bash builtin functionalities!

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How-To: Bash Parameter Expansion and Default Values

Posted by chantra on 28th January 2013

Bash is a sh-compatible command language interpreter that executes commands read from the standard input or from a file.
There is much more to bash than running a sequence of commands, one of the features bundled with bash is parameter expansion.

Any shell user has most likely used shell variables, be it $1 or $myvar, to save values... but there is more to it. This tutorial will cover a subset of shell parameter expansion that can become really handy and save you a lot of time.

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Mastering Top

Posted by chantra on 22nd January 2013

top is most likely one of the most known Linux command and also one of the most used one, however most people do not take full advantage of its capabilities.

In this tutorial, we will see a few usages of top that will make allow you to get more out of it.

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Posted in Administration, HowTo, System | 4 Comments »

How-To: OpenVPN on Debian Squeeze with Username/Password authentication

Posted by chantra on 16th January 2013

OpenVPN is a SSL based VPN software that runs on most OS. It is simple to install and run.

In this tutorial, I will go over the steps needed to configure OpenVPN on Debian Squeeze to provide a full VPN tunnel, this is particularly useful when you want to access internet from non-trusted networks such as free hotspots...

There are many ways of setting up OpenVPN, a common one is to use a unique certificate for each users. Another one is to have each user authenticate with a username/password.

In this article, we will be setting OpenVPN to authenticate users using PAM.

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