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Friday, October 22, 2010

Interesting Linux Commands.

Index:

1)Command to find the Installation date of O.S.

2)How to find Most Used Linux commands of your machine?
3)
Blink LED of Network Card to find physical port
4)Command to scare people.
5)Prevent accident Play safe use Echo.

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1)Command to find the Installation date of O.S.

Still dont remember last time you have installed an OS.
Dont worry Following command can help you get the exact date.

Method 1:

# tune2fs -l /dev/root | grep created
Filesystem created: Wed Oct 13 19:08:13 2010


Method 2:
First find the location of install.log in your machine.
# find / -name install.log
/root/install.log
then you can check the detail using ls -ltr /root/install.log.
# ls -ltr /root/install.log
-rw-r--r-- 1 root root 14038 Oct 13 13:40 /root/install.log
in above example install.log is created on Oct 13 So the OS is installed on 13th Oct.
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2)How to find Most Used Linux commands of your machine?

I know the question is quite simple but yet interesting.You can use following command to find out which is the most used command of your Linux Machine .

# cut -f1 -d" " .bash_history | sort | uniq -c | sort -nr | head -n 10
113 cd
98 ls
83 xm
64 cat
59 dir
59 df
55 find
48 sysctl
42 vi
36 mount

other way of doing the same thing.

# history | awk '{print $2}' | awk 'BEGIN {FS="|"}{print $1}' | sort | uniq -c | sort -n | tail | sort -nr
113 cd
98 ls
80 xm
64 cat
59 dir
59 df
55 find
48 sysctl
42 vi
36 mount


from above output its very clear that "cd" is the most used command in my distribution.
I know there are no practical usage of this command but sometime its good to know which command stress your fingers :)

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3) Blink LED of Network Card to find physical port corresponds network interfaces(eth0,eth1,...)... (Use this in-case of multiple network ports).

If you want to make sure which physical interface is eth0 and which is eth1 or eth2 and so on

run:

#ethtool -p eth0 20

This blinks the LED on the interface for five seconds–without interrupting network traffic.
More commands will be updated soon.

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4)Command to scare people.

Well this one is one of my favorite.

It just produces random sound from your machine.
I use this command for following usage.
1)To scare people.
2)To find the machine location especially when you dont know the physical location.

how it works ?
Just type
#dd if=/dev/urandom of=/dev/dsp
The random sound will start coming up from your machine.
Well this may not be the fun but imagine if you can scare your
colleague who sits in same LAN of yours.

Just use SSH to do this.

# ssh username@Ipaddressofmachine dd if=/dev/urandom of=/dev/dsp

It will then ask you the password just type it and you are done.

To stop the noise you can find the process using following steps.
Step 1: Find process id of dd command.
# ps -ef |grep dd
root 4861 1 0 11:35 ? 00:00:00 /usr/bin/hidd --server
68 5318 5311 0 11:36 ? 00:00:00 hald-addon-acpi: listening on acpid socket /var/run/acpid.socket
68 5323 5311 0 11:36 ? 00:00:00 hald-addon-keyboard: listening on /dev/input/event0
root 5556 1 0 11:58 ? 00:00:00 dd if /dev/urandom of /dev/dsp
root 5597 5571 0 11:59 pts/0 00:00:00 grep dd

As you can see from above output the process ID is
5556.

Step 2: Just kill it using.

# kill 5556
---Process id can be different please run step 1 to check whats your process id and substitute in front of kill.



5)Prevent accident Play safe use Echo.

Its always a good idea to foresee what would be the impact of your command.
for example
# echo rm *.txt

above command will not delete all the txt files but will display what files will get deleted if you run
#rm *.txt


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