Unusual linux commands can be very handy in several cases. Here are some of them.

Repeat the last typed command:

 

Display file-content like cat, but from upside down, can be achieved with tac (reverse cat)

 

Like to lookup in a dictionary file? Use look. Everything whats starts with the passed word will be shown.

 

Display time / date in bash screen on right upper corner. Continously!

 

 

Veröffentlicht unter linux.

Read Linux Tutorial Part1, before you start here.

Commands you have head about in Part1 are:
whoami, hostname, uname, uptime, clear, pwd, cd, echo, ~ and ..

 

In the second part of the Linux Tutorial, we will learn about dealing with files and folders (directory).

First move to your home directory with (change directory):

Now let us create a directory, named „garage“, with the „make directory“ command:

You have created the garage directory, but you are still inside your home directory. Go into the garage directory with:

Notice,  that the „change directory“ is by far the most important command. You will see, that you will use this command very often.
In the next step, you go „one directory up“, so that you will be in your home directory again. This can be achieved with:

Don’t forget the space between „cd“ and the two dots. The two dots is a sign for the directory above. There is a top-level directory, called the root. There is no directory above the root directory. You can go there with:

Again, there is a space between „cd“ and the „slash“. If you are curious whats inside the root folder, type:

The list command, with the parameter „l“, shows you the directories content. Time to go back into our garage directory inside our home directory. Go there with:

The tilde (press Alt-key + tilde-sign) is a sign for our home folder. And we want to go inside the garage folder, which is inside our home folder. We create now a file called „mycar.txt“ and write „bmw“ inside this file. Here we go:

The echo command simply displays the word in quotes, in this case „bmw“. The > character redirects the result („bmw“) into the file, which came behind the „>“ sign. Btw: a single „>“ always create an empty file, even when the file already exists. When you want to attach something to a file simply use „>>“. Let’s look into the file:

We want to copy the file mycar.txt:

And now we want to attach something to our new file:

Check the content of our new file with:

And check the contet of our garage folder with:

 

Veröffentlicht unter linux.

These tutorials explain the Linux operating system (os) step by step. Starting with simple examples and getting more advanced each lesson.

The line where we type in the commands is called the prompt, the blinking something right to it is the cursor.

Lets show who is logged in:

And the hostname of the computer can be shown with:

As you can see, username and hostname are contained in the prompt.

If you want to know the name of the operating system, you can use:

How long the computer is up (not rebooted since) shows the following command:

Clear all the stuff on the screen with:

If you using the arrow keys (up and down), you can browse between the commands you already entered.

When you want to know in which folder you are, use:

It’s short for: print working directory.

Let’s go to your users home directory by typing:

At this location, all the files related to your current user are stored. You home-folder is a special folder. The tilde sign „~“ is a synonym for your home folder. Instead of typing „cd“ you can type „cd ~“ as well. When you’re in your home folder you can see the tilde in the prompt. The tilde sign is a variable. You can output its content to the screen:

Create a directory named garage withe this command:

mkdir is short for: make directory

Most important command of all is „cd“. It means change directory. With this command you can browse in the directory tree.
Let’s switch to the directory „garage“ you recently created by typing:

The prompt, by the way, also shows you in which directory you are. (So you don’t have to type pwd all the time)

 

If I want to go back in the directory-tree, like one level up, we use:

Don’t forget a space between cd and the two dots. The two dots are a symbol for the upper (superordinate) folder.

If you type the first letters of a command, try to press two times the tab-key, and the command will be completed.
This will you save lots of time and is one of the most useful ways to increase your working speed.

Linux Tutorial Part2 >>

tcptrack

A quite handy tool for monitoring tcp traffic is tcptrack. Get it with:

and start it with

the interface parameter -i eth0 must be according to your needs, you can check your interfaces with ifconfig.

There is also tcpdump, tcpflow and other nice tools

Netstat

Sometimes one like to figure out what programs listen at a port. Here we can get an overview with:

Where t=tcp, u=udp, p=show program name, l=show listening ports, n= numeric (not resolve machine names)
The Output could look something like this:

 

lsof

With lsof you can determine easily which program listens on a port and under which user that program runs:

 

mtr

Need Ping  and traceroute combined in a single application? Use mtr (matt’s traceroute)

 

Let’s have a look which packages are already installed and show only those with „php“ in the name. A fresh system usually shouldn’t give any results.

Next you can check what kind of modules are available. Do it like this:

Now install the php7 base packages with the command:

Now install some other packages for php:

 

Try this out:

 

Veröffentlicht unter linux.

Sometimes it happens that you can’t use your services cause they deal with blocked ports. For exampel you use mysql on the commandline and it is by some reason denied. A proxy can help you. Tsocks helps you to use a proxy. Tsocks is a library for intercepting outgoing network connections and redirecting them through a SOCKS server.

install tsocks with

Configure the file /etc/tsocks.conf

and finally call your command like this:

 

 

List all Instances

Stop an EC2 instance

Start an EC2 instance

 

First find all the files you want to convert and store their filenames in a file

Iterate through that files and make a jpeg from them

Finally move all jpgs to a separate location if necessary

 

In reality you have quite often perform a certain command on several files. First i detect all files I’m looking for and store them in a filelist.

Second i run through this file, line by line and perform my command on all filename I’ve received one step before.

You need to replace in several files. You can do it with sed. Be aware about masking special chars. In the example below the string „my\folder“ is replaced with „your\folder“.
Replacing with sed works like this: sed -i s#old#new#g
The delimiter (in this case the #) can be changed. The first sign after the s acts as delimiter.