Category: Linux


Altering a process priority is indispensable when you wish to change the behaviour of a running program on the system. Most of the times, when one wants a program to complete its processing faster, tuning its priority holds the key.

Under Linux, this can be accomplished by two ways – GUI & CLI. For this article, we will look at changing a process priority the GUI way. The CLI warrants a separate article.

Once you have the process running, simply open the “System Monitor”. Do note, I am under KDE for this demonstration. So the system monitor options may vary as per your desktop environment. However, the corresponding options should be self explanatory.

Process Priority GUI

Once in System Monitor, click on the “Process Table” tab for a summary of running processes on the system. Here identify your program. In my case, I wished to increase the priority of the Openshot process so it may process my video faster. So upon highlighting the Openshot Video Editor’s process in the table, I hit F8.You should now notice a similar window like one shown above. Here drag the sliders to the right for faster processing. You will be prompted for the root password as you do so. That’s all, the process should now conclude faster.

Many a times, one needs to keep an eye on certain aspects of a system. Be it verifying transfer of contents over to a host or scanning log files as they are written to, these tasks need constant supervision. Wouldn’t it be better if there was some automation to accomplish this? Thankfully, there is one.

Most Linux distros have an inbuilt utility known as ‘watch’ which essentially keeps running a particular command, every ‘n’ number of seconds. The watch command is very simple to use.

Recently, I was rendering a video in Openshot. To my inconvenience, the progress bar within the Openshot failed to show any visual indication. Here I quickly fired up a console & navigated to the location where my video file was to be rendered by Openshot. After this, it was simply a matter of running the mundane ‘ls -lhtr’ command using watch. The ‘ls -lhtr’ lists the files by their recent modification times & presents them in human readable size output. I used the following format;

$watch -n 5 ls -lhtr

Watch Command

Here the ‘-n 5’ option tells watch to run the command ‘ls -lhtr’ every five seconds. One can notice the increasing file size of the file which was rendered by Openshot as the command ran at five seconds interval. Thus, I was guaranteed of Openshot doing its work smoothly despite the conked progress bar in GUI.

The ‘watch’ command is regularly used by system administrators to check the output of a log file as it is written to viz. apache access log. Of-course, one can even use the ‘tail -f’ command to check the output of the log file in this scenario. Watch is a nifty tool in any administrators toolbox and its utility is limited by your imagination.

A remotely exploitable vulnerability in bash has been discovered by Stephane Chazelas. The vulnerability has the CVE identifier CVE-2014-6271 and has been given the name Shellshock by some. This affects Debian as well as other Linux distributions. The vulnerability arises from the fact that you can create environment variables with specially-crafted values before calling the Bash shell. These variables can contain code, which gets executed as soon as the shell is invoked. The name of these crafted variables does not matter, only their contents. As a result, this vulnerability is exposed in many contexts.

This issue affects all software that uses the Bash shell and parses values of environment variables. This issue is especially dangerous as there are many possible ways Bash can be called by an application. Quite often if an application executes another binary, Bash is invoked to accomplish this. Because of the pervasive use of the Bash shell, this issue is quite serious and should be treated as such.

However, there is nothing to worry about as a patch has been issued. It is recommended to install it using your system software manager.

Bash Patch

You can verify the upgrade by running the following command. You should receive “Not vulnerable”.

$env check=’Not vulnerable’ x='() { :;}; check=Vulnerable’ bash -c ‘echo $check

Read more : https://securityblog.redhat.com/2014/09/24/bash-specially-crafted-environment-variables-code-injection-attack/

varnish

If you have a website, it is crucial it loads up fast so users get a good experience. There is a small piece of software known ‘Varnish Cache’ which can help your side load faster by caching its content. Varnish Cache is an open source web application accelerator also known as HTTP accelerator or caching HTTP reverse proxy. Varnish Cache can dramatically improve the site performance and depending upon your system architecture can speedup your website performance by 80% or more.
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Configure Static IP in RHEL 7

It is fairly simple to configure a static IP address in Red Hat Enterprise Linux 7.

First one needs to stop & disable the Network Manager service. We do so since we are going to manually enter our network parameters.

To stop & disable the Network Manager service issue;

#systemctl stop NetworkManager.service

#systemctl disable NetworkManager.service

Next issue the following command if you are not sure of the name of the interface you want to set the static IP for. [If you have a single network interface card(NIC) installed in your system, there would be only a single file with the NIC name in network-scripts directory & hence issuing this command is avoidable.]

#ipconfig -a

Next we need to edit manually the interface file. It is recommended you take a backup of this file first before editing.

#vi /etc/sysconfig/network-scripts/ifcfg-p2p1

Keep the default file parameters as they are & simply make the below changes.

BOOTPROTO=STATIC

ONBOOT=yes

IPADDR=192.168.1.71

NETMASK=255.255.255.0

GATEWAY=192.168.0.1

Save the file & quit Vi.

You should keep a note in your mind. Whenever you edit a network interface file, you must restart the network service for the changes to take effect. Since RHEL 7 uses ‘systemd’ to manage the services we issue the following command to restart the network service.

#systemctl restart network

(Though one can even use the old #service network restart)

Once the network service is restarted successfully, you can verify the new IP by;

$ifconfig

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