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CentOS, Debian, Linux, Ubuntu, Uncategorized

Using ssh without password

November 12, 2013by viniciusNo Comments
ssh without password

SSH without password

Access ssh without password, I think it’s one of the things, most useful for anyone who has to deal with multiple servers at the same time, especially for those who need to make copies of files between them.

To use this facility, simply installing the ssh-keygen , to generate the key machine. For this generation can use two types of encryption, namely, rsa and dsa

What is RSA?

RSA is an algorithm for data encryption, which owes its name to three professors from MIT Institute (founders of the current company RSA Data Security, Inc.), Ronald Rivest, Adi Shamir and Leonard Adleman, who invented this algorithm – to date (2008), the most successful systems implementation asymmetric keys, and is based on classical theories of numbers. It is considered the safest, since he sent away all attempts to break it. It was also the first algorithm to enable encryption and digital signature, and one of the great innovations in public-key cryptography.

source: http://pt.wikipedia.org/wiki/RSA

RSA is the most commonly used, mainly because it is the default ssh-keygen.

What is DSA?

DSA is an acronym for Digital Signature Standard (Digital Signature Standart), created by NIST, and specifies the digital signature for DSA and SHA-1 for hashing. The DSA is an asymmetric algorithm and the private key operates on the hash SHA-1. To verify the signature piece of code calculates the hash piece and another uses the public key to decrypt the signature, and finally comparing the results of both ensuring the author of the message. The DSA works with keys of 512 to 1024 bits, but unlike the RSA which is multipurpose, DSA ??signs only and does not guarantee confidentiality. Another against DSA is that the generation of the signature is faster than RSA, but 10 to 40 times slower to check the signature.

How does ssh-keygen?

The ssh-keygen , raises public and private keys, so that from them if you can access the server. Which in our case will occur without typing the password, but this key usage is as a hint, to improve the security of access to the server, of course, if using with password.

Hands on mass

Open your terminal, call your grandmother, and the whole family to watch.

Generating the keys

It is up to you which encryption use, so I made the explanation of the two. Since you’re with your family, make a poll to decide which is the best. After the vote, follow the tutorial, I’ll use the rsa, if uses dsa, just change where rsa, dsa.

log in to terminal, with the user that you want to access the server without password. Because the key is specific to the user.

 ssh-keygen-t rsa 

You will get the following response:

Generating public/private rsa key pair.
Enter file in which to save the key (/home/vinicius/.ssh/id_rsa):

My user is vinicius, I don’t know if you’ve noticed, but my name is that (see the url!).Finally, choose the folder in which to save the key. If ta with laziness only confirms.And you will receive another message.This step is very important

Enter passphrase (empty for no passphrase): 

As you read above, enter the password (the password). As we want to access without password, only, confirm (press enter, ask your grandmother!) without typing anything.He will ask for confirmation, press “enter” again. Confirmation:

Enter same passphrase again: 

Ready, created the key.

Your identification has been saved in/home/vinicius/.ssh/id_rsa.
Your public key has been saved in/home/vinicius/.ssh/id_rsa.pub.
The key fingerprint is ...

It generates a lot of cute character, that are not suitable to put in this post. Everything created, now we put the public key on the server, to which we want to access without password.

Putting the public key in the destination server.

There are a few different ways to do this step, even found a very interesting when writing this post. I will describe two, a simple, and another simpler still.

Simple mode

What must be done is to put the contents of the public key (id_rsa.pub) on the server, specifically the file authorized_keys in either user, the server, to which we have access.

Let’s assume that the user name is joao, on the server viniciusmuniz.com

First let’s copy the public key to the server

/home/vinicius/.ssh/id_rsa.pub scp joao@viniciusmuniz.com:/home/joao/

enter their password, their penultimate time to type it. And then access the server, and place the public key in the authorized_keys

ssh joao@viniciusmuniz.com
cat/home/joao/id_rsa.pub > >/home/joao/.ssh/authorized_keys

Ready! Now test the ssh access, that there will be no further need for password.

Super simple mode

This way I found writing this post. There is a facility that is the ssh-copy-id , which with just one command, he inserts the public key in the destination server.

 ssh-copy-id -i /home/vinicius/.ssh/id_rsa.pub joao@viniciusmuniz.com 

Accessing ssh without password

Now just login, there will be no more need for password. Join the fun!

 ssh joao@viniciusmuniz.com 
CentOS, Debian, Linux, Subversion, Ubuntu, Uncategorized

Discovering doors open server with nmap

August 22, 2013by viniciusNo Comments

nmap-project-logo

Hello, after a long time without writing, I finally found the time.

And in another tutorial, we’ll learn how discover open ports or closed on a server, computer …

nmap

For this task, we use the command nmap .

According to nmap’s own description, the application is:


Nmap (“Network Mapper”) is an open source tool for network exploration and security auditing. It was designed to track (Scan) large networks quickly yet works well with a single host (host). Nmap uses raw IP packets in (raw) on new ways to determine what hosts (hosts) are available on the net …

For more details you can find in http://nmap.org/ . I like to use nmap, but it does not mean that this is the only way to accomplish this task.

Listing the main server ports

The simplest of commands, just run nmap to the server that you want to investigate

nmap test.com

Listing the main server ports in more detail

nmap -s test.com

Verifying several machines on the network

Very useful for network administrators

Check certain ips
nmap 192.168.254.1 192.168.254.2 192.168.254.3
Verifying a track (one range) of IP’s
 nmap 192.168.254.1-10

Verifying a range using wildcard
nmap 192.168.254.*

Verifying a specific port

nmap -p [port] test.com

Verifying a range of ports

nmap -p 80-400 test.com

Again, this is not the only method of doing this scan. And you can find more about nmap the link: http://www.cyberciti.biz/networking/nmap-command-examples-tutorials/

CentOS, Debian, Linux, Subversion, Ubuntu, Uncategorized

Easy way to scheduling commands in linux

August 5, 2013by viniciusNo Comments
utilizando o comando at linux

utilizando o comando at linux

And alas! Let us understand more a Linux command, now the at . That also did not know until recently.

Imagine yourself in the following situation, you have to run a command now, so to come back from lunch (that’s damn silly example), but will only arrive at 14:30. and your boss wants the result of this command to 2 hours, or it will eat your … liver. Simple!! The command at will leave you with your … intact liver. Let’s practice, and stop bla bla.

The command behaves like a cron that will run, and then cease to exist. Much simpler than configuring a line in cron to run a command only once.

at practice

Assuming that the command that your boss wants to be shot tomorrow, and is the list of all users logged in at 14:00, by which it accesses a file on the network.

The command accepts multiple configuration variants of the date / time. For this example we use in this way

$ At 2pm tomorrow
at> who> / var / www / list_users.html

When you enter the command at it will open a “sub-terminal” at the for you to enter your command, in our case who> / var / www / list_users. html , to save at the command, use ctrl + d .

Tips command at linux

List commands (jobs) configured at the

Use command atq , it will list the work to be performed, for your user, if you are the root of all the users.

$ Atq

Delete commands (jobs) configured at the

Use command atrm , it will remove a specific job, you should specify the work to be removed. For example:

$ Atq
5 Fri May 17 13:30:00 2013 vinicius
6 Fri May 17 13:31:00 2013 vinicius

$ 5 atrm

Going deep in at

I advise to read the documentation at as there are many tips on the same

 man at 

For example:

Running a command in 3 days at 4 o’clock

at 4pm + 3 days

Running a command on a specific day (18.10.2013) at 4 o’clock in the morning

Observer this example, the date is in standard MMDDCCYY

at 4am 10,182,013
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